Do Orchids Need Cooler Night Temperatures?


Whether phalaenopsis truly need distinctly cooler night temperatures is debatable. Photo: &

One persistent semi-myth about growing orchids is that they need a distinctly cooler night temperature in order to bloom. It’s only a semi-myth, because there are indeed orchids (and in fact, many of them) that do need truly cool night temperatures: think of hardy orchids like slipper orchids (Cypripedium spp.) or many of the dendrobiums (Dendrobium nobile and others). However, 99% of orchids sold today are moth orchids (Phalaenopsis cvs) and their need for distinctly cooler night temperatures is … debatable.

Things Have Changed

The official recommendation I was given when I first started growing phalaeopsis orchids back in the 1980s was that they needed 70–80ºF (21–27ºC) days and 55–65ºF (13–18ºC) nights starting in the fall to order to initiate bloom. (Nighttime temperature dips during the spring and summer have always been considered less vital to flowering.) 

The first part was easy enough: 70–80ºF (21–27ºC) are average indoor temperatures. But 55–65ºF (13–18ºC) nights: geez! I gardened at the time in an apartment with pretty much no temperature control. There was no way I could offer them nights that cool. So, I just gave my phals the best care I could and hoped for the best. And guess what? They did bloom!

The reason is partly because such strict temperature ranges really weren’t that necessary to start with. (Early orchid growers were likely a bit too zealous in their advice!), but also because phalaenopsis have, over time, adapted to “normal indoor growing conditions.” 

tiny orchid Phalaenopsis equistris
Phalaenopsis species, like this Phalaenopsis equistris, are often smaller than modern hybrids with smaller flowers and some (although not P. equistris) really do need cool night temperatures in order to bloom. Photo: Kroton, Wikimedia Commons

The original species, phalaenopsis taken directly from the wild, may indeed have had distinct night temperature preferences (at least, some of them did), but as hybrid varieties came to dominate the market, that became less and less true. The ones that bloomed the best were kept and those that weren’t so satisfactory were eliminated. And thus gradually “easier to grow” phalaenopsis, often ones that bloomed more than once a year, began to take over the market. And one factor in making orchids “easier to grow” included the lesser need for a distinct night temperature change during the fall and winter months, so hard to give in the average home. 

This is actually common with almost any cultivated plant. By choosing the most successful subjects from even a “difficult” plant, using those in crosses and keeping, again and again, year after year, the best performing plants of each generation, our garden plants have become less wild and more adaptable to cultivation. Some are no longer even capable of growing in the wild anymore! And so it is with orchids as well.

Even by the 1980s, this was already happening, whence my success with phalaeopsis orchids in spite of having no temperature control. It’s even more the case today. It’s hard to find a hybrid phalaenopsis today that really needs at nighttime temperature drop to 55ºF (13ºC) in order to bloom!

If You Can…

Hybrid phalaenopsis and thermometer
A slight nocturnal temperature drop can sometimes be useful. Photo: &

A bit of a nighttime drop is still helpful. Cooler nighttime temperatures allow orchids to slow down and store carbohydrates rather than expending them all night. But they’re unlikely to need a precipitous drop. Even a 5ºF (3ºC) drop from the daytime temperature (whatever it is) usually suffices these days, and that’s usually easy enough to give … with no effort on your part! 

First, sunlight during the day warms up leaves that then cool down when the sun goes down in the evening. You don’t have to do anything special to take advantage of that. Plus, cooler nighttime air outdoors in fall and winter tends to cool the air just inside the window, so plants on a windowsill typically do profit from a bit of a temperature drop even on cloudy days. Even plants growing under lights in a basement far from any natural light tend to cool off a bit when the lights are turned off at night. 

That’s why most phalaenopsis automatically profit from somewhat cooler nights even if you don’t do anything special … and that’s generally enough for them to bloom.

That said, if your phalaenopsis is growing vigorously, but still fails to flower, you might want to try and find a way to give it a good 10˚C (5ºC) temperature drop at night. You just might have a recalcitrant phal not as adapted to modern ways!

Yew Suffering From a Sexual Identity Crisis


Hey, Taxus × media ‘Densiformis’! Are “yew” a male or a female? Photo:

Question: Could you tell me if the hybrid yew ‘Densiformis’ (Taxus × media ‘Densiformis’) produces arils (berries)? While searching on the Internet, I found little information and much is contradictory. Some sources say the ‘Densiformis’ yew is a female cultivar, but none say whether it requires a male plant for pollination. Other sites say this cultivar does not produce fruit, but others suggest it produces a lot of arils! 

If you were able to clarify all of this, I would be very happy!

Alexandra Paré

Answer: There is nothing that looks so much like one yew (Taxus spp.) as another yew. Their correct identification is therefore very difficult and that results in a lot of confusion.

The “real” ‘Densiformis’ hybrid yew is a dense, spreading yew with dark green needles very popular in foundation plantings. It is indeed a female cultivar and yes, it does produce a quite a good crop of very attractive bright red arils, but only in the presence of a male yew.

Taxus × media with red berries.
The red berries (arils) of Taxus × media ‘Densiformis’. Photo: American Conifer Society

As the pollen is carried by the wind, the male can still be a certain distance away. However, the further away it is, the less reliable berry production will be. So, with female yews being used more often in landscaping than males, you often see ‘Densiformis’ hybrid yews that remain berriless for lack of any male nearby to pollinate them or, at least, that only rarely produce any berries (occasionally a female yew will sometimes produce an aril or two without pollination).

Taxus × media ‘Densiformis sans baies
Sold as Taxus × media ‘Densiformis’, this plant’s lack of berries could mean it’s an impostor… or just that there is no pollinator nearby. Photo:

But in addition to that, there is a lot of confusion in horticultural circles and some yews sold under the name ‘Densiformis’ are actually male. It’s practically impossible to know which nursery sells the real ‘Densiformis’ (female) and which sells the impostor.

Ideally, if you want the real thing, therefore female, you’d look for a specimen that already bears at least one aril at the time of purchase. And if you want many red berries, be sure to plant a yew known to be male, like T. × media ‘Hillii’, not too far away, to act as a pollinator and thus ensure good fruiting.

Garden Myth: Aspirin as Rooting Hormone


Photo: &

Question: Can you use aspirin as a rooting hormone?

Zofia Walnik

Answer: No, or at least, you could, but it won’t likely be of any help.

Of course, information to the contrary abounds on social media. Usually one of two methods is recommended:

1. Adding a regular strength aspirin tablet to a glass of water and rooting the cutting in the resulting solution.

2. Adding a regular strength aspirin tablet to a glass of water and soaking the cutting for 1 hour before inserting it into potting soil.

Neither of the two methods will get any notable boost from the aspirin. The second method will be more successful than the first, though, because cuttings rooted in potting soil grow much more vigorously than those started in water. (Read Starting Cuttings in Water: Not Such a Good Idea to better understand why.) But that has nothing to do with the aspirin treatment.

Two brands of aspirin, one labelled ASA.
Aspirin may also be labelled ASA. Photo: Daniel Case, Wikimedia Commons

Aspirin is acetylsalicylic acid (ASA), very similar to the salicylic acid that plants themselves produce when they are stressed. Used at very low doses (it’s toxic at high doses), ASA has all kinds of beneficial effects on humans, but very little on plants.

In different studies, ASA was generally found to have no effect on rooting. In the few cases when it did, it tended be more likely to inhibit rooting than to stimulate it, although in some cases there was a very slight beneficial effect. However, either way, the effect, positive or negative, was so slight that “the results were not scientifically valid.” In other words, the effect of aspirin on cuttings is not worthy of mention. So, essentially, you simply waste an aspirin tablet when you apply one to a plant cutting.

But precisely, since aspirin has essentially no effect, people who use it cry victory when their cuttings take root and then spread the good news on Facebook, Twitter, etc., without thinking that if they had not used aspirin, the result would likely have been just as good, even slightly better in some cases. 

Most soft stem cuttings produce their own rooting hormones and don’t need outside help. That’s why rooting cuttings is so easy!

Cutting with rooting hormone applied.
For plants that are difficult to root, applying rooting hormone gives the best results. Photo:

For cuttings with semi-woody and woody stems, which are more reluctant to root, there are commercial rooting hormones that help a lot. But aspirin? It’s just a waste of time!

To learn more about the art of taking cuttings, read Rooting Cuttings Step by Step.

Pee Planters May Save Lives in Amsterdam


GreenPee planters have a urinal on the side. Photo:

12 new green urinals have been installed in Amsterdam to stop “wild peeing” … and they may also save some lives to boot.

The urinals, called GreenPees, produced by the Dutch company Urban Senses, look like traditional planters and have plants growing from the top. But there is also a target zone for urination on the side. The goal is to reduce public urination, an age-old problem in Amsterdam that damages buildings, creates undesirable odors and can be a health problem.

GreenPee planter near canal
I find this GreenPee a bit too close to the canal, don’t you? Photo: GreenPee

And lives may be saved. According to the tourism information site DutchAmsterdam, nearly 15 inebriated men drown every year in Amsterdam after losing their balance while peeing into a canal. So, guys, play it safe and pee into the pot, not into the canal!

4 GreenPees were placed around Rembrandtplein square in a pilot project in 2018 and resulted in a reduction of 49% in wild peeing. No estimate was made of lives saved, but then, the Rembrandtplein is one of the rare spots in Amsterdam that is not located on a canal.

How They Work

Man urinating into a GreenPee planter.
You can readily find men eager to demonstrate how the GreenPee works. Photo: S. Boztas,

The GreenPees are installed in public places, especially near bars where large quantities of beer are consumed. One side of the planter (or two sides, if you prefer to pee with a friend) has a clearly marked target where the pee deposit can be made. The tank inside is filled with odor absorbing hemp fibers: it is fully self-contained and no flushing is required, thus no water is wasted. After composting, this fiber-urine-mixture becomes a phosphate-rich organic fertilizer used to fertilize the city’s green spaces.

A wide range of plants can be grown in the container which has a water reservoir and a wicking system to reduce watering needs.

As far as I know, pea plants are not among the plants so far tested.


When I first heard of the GreenPees, I assumed that the urine was being used to water the plants directly, which seemed like a wonderful idea, but apparently that would be too much of a good thing. Some have more than 75 pee visits per day! The poor plants would quickly be overcome by the quantity. Instead, the container inside, which can handle up to 300 pee visits, is regularly emptied. A smart sensor can be included to warn the operator when it’s time to do a round.

The GreenPee is presently still a strictly male-oriented device, but research is underway on developing a LadyGreenPee.

Growing Vegetables Indoors Over the Winter: Not So Simple!


Don’t believe it when magazine articles and blogs promote growing vegetables indoors as something the average home gardener could do: it’s not easy, but instead very difficult. Photo: Kang Starr

As I write this in mid-fall, I’ve just leafed through yet another magazine article about easy it is to grow vegetables and herbs indoors over the winter. Pretty clearly, the writer never tried it. It was essentially nonsense: beautifully illustrated nonsense, but nonsense just the same.

Growing vegetables (and herbs) indoors is not easy, especially if by that you mean growing vegetables to full maturity. It’s damn hard! A challenge even for expert gardeners. And it’s expensive to boot! By the time you install the equipment necessary to really grow vegetables indoors, we’re talking $40 head lettuce plants. Ouch! 

Now, I’m not talking here about starting seeds indoors you’ll be planting outdoors later—that’s easy enough —, but rather vegetables you can really grow from seed to full maturity in your home during the dark days of fall and winter. The grocery list would ideally include tomatoes, peppers, lettuce, celery and others: the same veggies you normally grow outdoors during the summer. Is that even possible?

My answer is a very timid yes, but it isn’t going to be easy.

Fighting Mother Nature

Mother Nature getting a sucker punch.
Growing vegetables indoors is essentially fighting Mother Nature. Ill.:, &

The important thing to understand is that by forcing vegetables to grow under indoor conditions in the off-season, you’re fighting Mother Nature every step of the way. It’s like trying to raise fish on dry land and thinking you can do so just by spraying them regularly with water. Vegetables abhor short days, low light and dry air and so grow poorly, weakly and produce less. Insects and diseases, many that scarcely ever attack them outdoors, quickly move in: there’s nothing they like better plants suffering from severe trauma.

If growing vegetables indoors had been easy, we would have known about it long ago. Humans have been growing vegetables outdoors for at least 2,500 years. They were living in huts and log houses at the time, often right next to the vegetable garden, yet they never succeeded in growing vegetables indoors. I think it’s telling that a hundred generations of vegetable gardeners exclusively grew their vegetables outdoors.

One thing that 2,500 years of vegetable gardening has taught us all is that you get the best results when you give the plant what it wants. That works every time. Vegetables like growing outdoors in full sun (or nearly full sun) with plentiful moving air, regular rains, high atmospheric humidity and rich soil. And growing plants indoors—again, in fall and winter, when light is exceedingly rare and the air is desert dry—means putting plants in an environment where they don’t get what they want. It’s practically like plant torture.

Large-scale greenhouse planting of pepper plants.
Even greenhouse growers struggle to maintain a suitable indoor environment for vegetable production. Photo: Aqua4D

Of course, I’m sure some readers will say, “What about those commercial greenhouses that grow tomatoes and peppers under glass?” Yeah, that works … but only because the greenhouse staff practically bends over backward to make the greenhouse environment as much like outdoor conditions as possible. They invest millions in making that happen, controlling every little aspect of care. I’m not sure you can turn your living room or basement into a reasonable facsimile of an outdoor vegetable garden with the kind of budget you’ll likely want to invest in it.

Lack of Light

Seedlings etiolated from lack of light.
Etiolated seedlings struggling to survive under a lack of light. Photo: gardenbettycom

The main limiting factor in growing vegetables indoors in the winter is light. Meeting the plants’ other needs is fairly simple. We already heat our homes and vegetables need about the same temperature as people. Watering is easy to organize (just don’t forget!), humidifiers are widely available to bring atmospheric humidity up and there is a wide range of soils, fertilizers, pots, etc. you can use. But where are you to get the intense sun that vegetables prefer?

That’s not a problem in the summer outdoors or even indoors in front of a large south-facing window at that season, but in autumn and winter, with their short, gray days and the sun’s reduced intensity? Just being behind a glass window that isn’t sparkling clean can reduce the light plants receive to half what they would get in summer. By mid-winter, as far as a tomato plant or a lettuce plant is concerned, a windowsill is pretty much as dark as Hades.

From Laidback to Excessive

A truly laidback gardener would simply grow their vegetables outdoors in the summer, the way Ma Nature intended it. But there are ways of growing vegetables indoors over the winter. Let’s look at them one by one, starting with the easiest methods and working towards the difficult (and expensive) ones.

1. Sprouts

Sprout container being rinsed.
Anyone can grow sprouts: no horticultural knowledge is needed! Ill.: Claire Tourigny, from the book Les idées du jardinier paresseux: Potager

Many vegetables and cereals are a snap to sprout as sprouts and the only equipment you need is a Mason jar and a piece of plastic mosquito screen. Plus, the technique is certainly simply enough.

Just pour about 1 or 2 tablespoons of seeds into the jar. Cover the opening with a piece of mosquito screen and hold it in place with the metal screw band of the lid (you won’t need the flat part of the lid). Now cover the seeds with 2 inches (5 cm) of cool water and soak overnight. In the morning, drain, then pour in more cool water, swish the seeds around to rinse them well, then drain again. From now on, twice a day, pour in enough cool water to cover the seeds, shake a bit, then drain well. Your sprouts will be ready in about 5 to 10 days (each type has its own schedule). You’ll know they’re ready when there are roots visible, but the first leaves (cotyledons) aren’t yet fully developed.

No light at all is needed at first, but after two or three days, a bit of natural sunlight will give greener sprouts with a stronger taste. You’ll have to experiment a bit on that level: some people find paler sprouts tastier than green ones.

Keep several sprouting jars going with various seeds at various stages of maturity so you’ll have something to harvest daily.

Why are sprouts so easy to grow? Because you harvest them at a very young stage, when they’re still living off the energy stored in the seed and before the lack of intense light harms them … and before anything has time to go wrong! 

You can read more about growing sprouts in this article: Sprouts: Fresh Home-Grown Greens All Year Long.

2. Microgreens

3 small trays of microgreens
Microgreens are just like sprouts, but a bit more mature. Photo:

These are almost the same as sprouts, but you sow the seeds in soil … and harvest them a few days later than sprouts, in about two weeks, when the cotyledons (first leaves) are fully developed. For microgreens, more intense lighting is required or they will etiolate (stretch for the light), as they no longer rely totally on the energy stored in their seed. A place on a sunny window (winter sun does suffice) or under a fluorescent or LED lamp, for example, will be needed.

You can harvest microgreens with scissors, cutting them off at the base, or pull them out of the potting mix and rinse them well to remove any soil particles, as their roots are edible too.

You need to start new cultures every two weeks or so to always have fresh microgreens on hand through the fall, winter and early spring.

You can read more about growing your own microgreens here: Indoor Gardening All Year Long With Microgreens.

3. Salad Greens Under Artificial Light 

Leafy vegetables growing under lights.
Growing salad greens under artificial light is fairly easy, but don’t wait too long to harvest them. Photo: Unemployed Redneck Hillbilly Creations

Leafy vegetables require less light than fruit-producing vegetables and root vegetables and ripen more rapidly. That means you can grow them indoors without too many complications. However, not in front of a window; at least, not in the fall or winter: there just won’t be enough light to grow healthy leaves. However, with a simple shop-type LED or fluorescent lamp suspended over a table or a shelf, you can grow leafy vegetables anywhere: in the basement, the attic, under a staircase, in a closet, etc.

You’ll need an inexpensive timer to make sure your plants get the light they need each day. I set mine to 14 to 16 hours to encourage a bit of extra growth.

Growing leafy vegetables under lights is certainly simple enough to do. Just fill pots or trays with moist soil (I prefer potting mixes that contain mycorrhizae, i.e. beneficial fungi) and sow the seeds about ½ to 1 inch apart (1–2 cm), barely covering them with mix. You can also use hydroponics and raise them without soil: that works too.

Adjust the height of the lamp so it is about 6 inches (15 cm) above the trays or pots. As the plants grow (and they’ll grow very quickly!), raise the lamp so it remains about 6 inches (15 cm) above the plants themselves.

Water as needed when the soil is dry to the touch, adding a little seaweed fertilizer to the irrigation water when you do.

How you maintain your plants as they grow depends on you, though.

Leafy vegetables growing under lights.
If you prefer, you can give the greens individual pots and let them spread out a bit. Photo:

Some gardeners like to grow their vegetables well spaced so each produces a nice individual rosette. If so, transplant the seedlings into individual 4- to 6-inch pots (10–15 cm) when their leaves start to touch. The maturity rate will vary, but, to give you an example, most lettuces will form a beautiful small but ready-to-harvest rosette in 40–60 days.

I prefer to harvest my greens without going through the hassle of transplanting. This close spacing gives a sort of hodgepodge of leaves where the individual plants aren’t too recognizable, but they will be ready to harvest sooner, in about 20 to 30 days, when they are about 6 inches (15 cm) tall. Just cut them about ½ inches (1 cm) from the ground … and let new leaves grow back. This “cut and come again” method normally gives a second harvest, sometimes even a third.

With either method, make successive plantings from early fall right through the winter so you’ll always have fresh salads to harvest right through until the outdoor gardening season begins.

Young mesclun plants
Mesclun, a mix of salad greens, is popular. Photo:

You can grow most leafy vegetables following one or the other of the methods described. If you’re just starting out, I suggest trying mesclun (a mixture of greens): it will give you a bouquet of flavors in little space. Or sow individual varieties, such as lettuce (leaf lettuce grows the fastest), spinach, arugula, beet (for its leaves), etc. You can also grow several herbs this way, notably basil, coriander (cilantro) and parsley, although parsley is very slow growing.

As for root vegetables, the easiest to grow indoors is certainly the spring radish: just follow the method described above. For other root vegetables, use deeper pots, space the plants more carefully … and stick to baby vegetables: baby carrots, baby beets, etc.: they’re faster to mature. It isn’t as easy to grow full-size root vegetables in a pot!

Rotating light garden with vegetables
The ultimate indoor salad green grower involves a garden that rotates around an extremely intense light. Photo:

Plus, for the serious gardeners willing to pay a fortune for homemade veggies, there are all kinds of even more specialized lighting systems using LED or fluorescent lights, from AeroGarden type systems with all sorts of sophisticated controls that give you a small quantity of very expensive greens right up to rotating light gardens that slowly spin around a light source, a system so sophisticated it will wow all your friends … but I’ll leave that to the fanatics!

To discover the wide range of possibilities, visit a hydroponics shop. There is certainly a hydroponics shop in your neighborhood.

4. Combine Sun and Artificial Light for Fruiting Vegetables

Tomato seedlings etiolated from lack of light.
Though they grew right in front of a window, these tomato seedlings just aren’t getting enough light.

I’m not a great fan of growing fruiting vegetables (tomatoes, cucumbers, eggplants, beans, etc.) indoors for a winter harvest. They tend to be very tall, very needy plants that grow weakly when they don’t get enough light. Plus, they are slow to mature, taking months, not weeks like leafy vegetables … and the longer you grow a plant under less-than-ideal conditions, the more things are likely to go wrong. But if you insist on trying…

Tray of tomato seedlings under lights near a window.
Combining natural light and fluorescent or LED lights will give the intensity fruiting vegetables need. Photo:

The cheapest way to go is combining natural sunlight and artificial lighting. You could, for example, hang a high intensity LED or fluorescent lamp over plants placed near the brightest window possible, raising the lamp as the plants grow (keep them about 6 inches/15 cm from the top of the plants). I suggest using dwarf varieties of fruiting vegetables, such as those designed for growing in patio pots: small determinate tomatoes, patio cucumbers, dwarf French beans, etc. That’s because adequately lighting tall plants under ordinary LED and fluorescent lamps is very difficult: usually only the upper leaves get enough light and, even with a window right nearby, the lower leaves struggle.

5. Grow Room

Or convert a room in your home into a grow room.

Grow op installation with mylar paneling and grow light, buckets with vegetables growing.
Modelled on grow ops, grow rooms make it possible to grow fruiting vegetables like tomatoes and peppers indoors… but at what cost? Photo: Kang Starr

This is the same technology commonly used for growing marijuana indoors: 400- to 1000-watt high-intensity discharge lamps (HID lamps) installed on the ceiling providing light as close as possible to sunlight in intensity and in quality. This will likely require major modifications to your home: an additional electrical box, a special air conditioning system, a CO2 generator, etc. Expect to pay handsomely just to get started … and there will be a big electric bill to pay every month as well. You can grow your veggies in potting soil or hydroponically: the choice is yours. As you can imagine, though, you’ll have to grow a lot of vegetables to make this veggie grow op worthwhile.

A Final Word

So, going back to our original question, about whether it is possible to grow vegetables in indoors even in winter… Yes, it is, but I still suggest sticking to sprouts, microgreens and leafy vegetables. Leave the fruiting veggies to real indoor vegetable gardening maniacs … or just wait until summer and grow them outdoors which is, after all, where they want to be!

Article adapted from one originally published on November 5, 2015.

Lead Can Still Be a Problem in Urban Soils


Lead is still poisoning urban soils. Photo:, &

I had a horrible scare back in the mid-1980s. A news report came out about children in my neighborhood being poisoned by eating lead paint and the report further suggested that vegetables grown near old painted walls could be contaminated with lead.

Of course, where was I growing my vegetables, but right at the base of a very old wall indeed, one dating back to the 1850s, with plenty of ancient paint flaking off? I think I drove my city counselor half crazy with calls insisting that my 4-year-old son and the soil of my garden be tested right away! Well, both were: my son, right away; the soil, eventually. My son was fine (we had only just moved in and had only harvested the very earliest spring vegetables). But soil was indeed contaminated. Over 4,000 ppm of lead, if I remember correctly. I was told to not grow root vegetables there are all, that leafy vegetables needed to be thoroughly cleaned and rinsed, but that fruiting vegetables would be fine. (Those were the recommendations back in the 1980s.)

However, fat chance I’d take the risk of growing anything edible in that lead-tainted soil! I had a child to think of and children are much more susceptible to lead poisoning than adults. I had already pulled out all that first year’s crop after the initial report and put them straight into the trash. I didn’t even dare put them in the compost bin! And I started vegetable gardening in a community garden, far from any paint, the following spring. 

The old vegetable garden became a flower bed for the next few years, until we moved into a newer development in suburbia where we still live. Although, due to its lesser age, our current home is not as likely to have been contaminated with lead-based paint, I still put the vegetable garden far from the house … and there it remains. Once burned, twice shy!

So, the original incident happened nearly 40 years ago. Lead paint and leaded gas were banned in most developed countries somewhere between the mid-1970s and the mid-1980s.

What’s the situation today?

What follows is an article by Anna Wade of Duke University from the excellent site, Soils Matter, Get the Scoop! of the Soil Science Society of America, a go-to source for valuable and honest information on the soils we garden in.

Is lead contamination ancient history?

Lead’s use may be—but we still have a lead problem, especially in urban areas.

The first extraction of the metal lead from ores was ancient—around 7,000 BCE. In the millennia since, Egyptians have used it in cosmetics, Romans in their pipes, the British in their ammunition and now every society in lead-acid batteries.

And, if it were not so toxic to humans, the use of lead would still be widespread in our daily lives.

Lead is a “heavy” metal, meaning it’s a dense element. Lead is also soft, malleable, corrosion resistant and distinguished by a low melting point. That’s what gives it its useful characteristics.

Wall with peeling paint
Lead used to be in common household paints until the 1970s. If you live in an older home or apartment, have the paint tested. Chipping and peeling paint is hazardous. Credit: Rachel Leege

Yet lead is a highly poisonous metal. Its presence disrupts almost every organ in the body if inhaled or swallowed. Lead displaces other metals in the body, such as calcium and iron, disrupting chemical reactions. The most problematic effects are on children. By mimicking calcium, lead can enter a child’s developing brain and disrupt the functioning of mitochondria.

Currently, there is no known “safe” level of blood lead concentration in children. Since 1960, the Center for Disease Control’s advisory level for blood lead has dropped from 60 micrograms per deciliter to 5 micrograms per deciliter.

In the United States, risk of lead exposure is becoming more of a thing of the past. In the 1970s, lead-based paint was common, as it increased the paints’ durability and sped drying. It was also used in “leaded” gasoline, which made car engines of that generation (and prior) work more smoothly.

Old classic care
Classic old car engines relied on lead in the gasoline, but its use was banned due to environmental reasons in the 1970s. Credit: Tom Rumble via unsplash

Unfortunately, the lead from gasoline was also sent into the atmosphere through car exhaust. It landed in the soil everywhere. The higher the concentration of cars—like cities and highways—the more lead.

Lead paint is a big risk for children. Medical studies showed lead exposure affected learning abilities and other health issues—especially in children. Lead paint that peeled off—or created dust—could be ingested or inhaled. This is especially true close to exteriors of older homes, around windows and other locations where lead paint was used.

Luckily, the U.S. banned manufacture of lead-based paint in the late 1970s. The EPA mandated a nearly 100% reduction of lead in gasoline by 1986. Between 1980 and 1991, mean blood lead levels of children ages 1 to 5 dropped by 77%.

Despite the phase out of lead in paint and gasoline, urban soils remain recognized as a leading source of lead exposure. That also goes back to lead being a heavy metal. That character means it tends to accumulate in soils and remains bioavailable for long periods of time.

Once deposited, lead remains strongly bound to clay and organic matter in the topsoil. Lead is not taken up in substantial amounts by plants, nor does it easily leach or migrate further down in the soil. Instead, this lead remains as part of the reservoir of urban soil and dust, susceptible to resuspension during dry periods. This resuspension is why children’s blood lead levels are believed to peak during the summers and reach a minimum in the winter.

There is some good news. A recent study in New Orleans reported an approximate 45% decline in soil lead over the span of 15 years.

Fire hydrant with flaking paint
Fire hydrant in Durham, NC with chipping lead-based paint. Photo taken in 2019. Credit: Anna Wade

Currently, a group of students and faculty at Duke University are mapping soil lead concentrations in Durham, North Carolina. We’ve collected street-side soils along 40 km of roadways in the city, and we’re currently sampling over 60 houses throughout the city. The results show there is still widespread lead contamination from before regulations went into effect.

Your average soil will naturally contain about 25 parts per million (ppm) of lead. Street-side soils in Durham currently have 245 ppm of lead on average. Sites that are across from old gas stations, fire hydrants and older buildings have lead levels up to 3,000 ppm. Our only point of comparison is a 1976 study, which found 2850 ppm of lead in street-side soils.

This means that in some parts of Durham, lead levels may have dropped 90% from their peak values. Our results suggest urban soil lead is on average declining in Durham, but hotspots of contamination persist.

While the primary sources of lead emissions are in the past—leaded gasoline and lead-based paint—urban soil lead contamination is not. By mapping urban soil lead levels, we have a greater chance of making childhood lead exposure become ancient history.

Are You Concerned About Possible Lead Contamination in Your Garden? 

If you live in an urban core or garden at the base of an old building with painted walls, maybe you should be! Here are some things you could do*: 

Vegetables in a wire basket being rinsed by a hose.
Rinse potentially contaminated vegetables outdoors. Photo: Lee Valley Tools
  1. Don’t locate food gardens next to a busy road or a home built prior to 1940 with a painted wooden exterior.
  2. Contaminated soil particles are more likely to cling to or become embedded in leafy greens (lettuce, spinach) and root crops (carrot, turnip) and they are therefore likely to contain high lead levels than fruiting vegetables like tomatoes and cucumbers.
  3. Always wash all vegetables and peel all root crops before they are cooked and eaten. Remove the outer wrapper leaves of cabbage.
  4. Wash off excess soil from root and leaf crops outside the house, preferably at an outside hose bib, to prevent bringing contaminated soil into the home.
  5. The amount of lead absorbed by plants is affected by the soil pH, organic matter and phosphorus content of the soil, and total soil lead level. To reduce lead uptake by plants, adjust the pH of the soil to a level of 6.5 to 7.0. Add organic matter such as compost, manure, leaf mold, or grass clippings to the gardening site. Add phosphorus to the soil as recommended by a soil test.
  6. In heavily contaminated soils adjacent to a residence, don’t grow vegetables. Instead, plant trees, shrubs or perennials and mulch the area to keep the soil covered. Soil removal and replacement should be considered if the soil lead level is over 5000 ppm total lead.
  7. Food crops should not be grown in soil that is over 400 ppm total lead. Use containers for gardening or cover the soil with landscape fabric and fill at least 8 inch (20 cm) high raised beds with a mixture of clean topsoil (low in lead) and compost.
  8. Don’t allow young children to play in contaminated soils. Frequent hand washing and rinsing outside toys will reduce the amount of soil ingested. Always wash hands before eating meals or snacks. Have family members leave outdoor shoes in a cardboard box at the door, to avoid spreading lead contaminated dust through the home. Rinse and launder gardening clothing promptly. Mulch play areas with wood chips or other soft materials to reduce soil dust.
  9. Parents of children under age 6 living in areas with contaminated soils should consult their physician. A blood test to monitor lead levels may be recommended.

*Information obtained from the website of the University of Maryland Extension.

Garden Myth: Sterilize Garden Tools With Vinegar


Contrary to popular belief, vinegar is not a good product for sterilizing cutting tools. Photo: &

Question: I was told to wipe my pruning shears with white vinegar to sterilize them between cuts. It’s apparently more ecological than using bleach.

Answer: True enough, but does it kill microbes? After all, the idea of sterilizing tools before reusing them is all about killing all microbes that could be carried from one plant to the next or from an infected part of the plant to a healthy one. And no, vinegar does not kill all microbes. It may be deadly to some, but is harmless to others.

So, no, don’t use white vinegar (or any vinegar) to wipe your garden tools between cuts.

Bottle of bleach with an X through it.

But then, neither should you be using household bleach! There are more details in the article Gardening Myth: Sterilizing Pruning Tools with Bleach, but in a nutshell, while bleach will sterilize pruning tools, it will also corrode and blunt them; plus it is awkward and dangerous to use (it’s irritating to the skin and dangerous to the eyes), stains and damages clothes and will ruin your gardening gloves. Plus, it’s extremely toxic to plants and can damage the tissue of the next cut.

So, bleach is certainly not something you should be using to sterilize pruning tools either!

What To Use to Sterilize Cutting Tools

The classic product for sterilizing garden tools is rubbing alcohol (isopropyl alcohol). It kills microbes, then quickly evaporates, so doesn’t harm the cut surfaces of the plant, nor does it corrode tools. Also, it’s harmless to clothing and garden gloves, is only an irritant if used repeatedly and can be easily carried around in your pocket in a small bottle.

Bottle of hand saniitizer

And in the COVID-19 era, you may already be carrying around hand sanitizer. Well, it’s also usually alcohol based (indeed, it is often largely isopropyl alcohol), so it will sterilize tools perfectly well, although do let the product evaporate from the tool (gels especially tends to be slower to evaporate than rubbing alcohol) before making another cut, as it can damage plant tissues. 

Other sterilizing liquids you could try are household cleaners, like Lysol, Pine-Sol or even an antiseptic mouthwash like Listerine. As with hand sanitizer, let them evaporate before making the next cut.

But just say no to vinegar and bleach!

Expansion of Huntington’s Chinese Garden


View from the Stargazing Tower, one of the new pavilions in the expanded section of the Chinese Garden. The Stargazing Tower offers sweeping views of the lake and garden below and of the “borrowed landscape” beyond, including the San Gabriel Mountains and Mount Wilson Observatory, which inspired the pavilion’s name. Photo: Aric Allen, © The Huntington

The Huntington Library, Art Museum, and Botanical Gardens in San Marino, California, simply called “The Huntington” by its admirers, is one of my favorite gardens. I’ve been able to visit several times and always come away impressed. There is so much to see, you’ll certainly need two or more days, especially if you want to visit not only the gardens, but the museums as well. Among the gardens are the fabulous Desert Garden, said to contain the largest collection of cactus and succulents in the world, the Japanese Garden, the Jungle Garden, the Australian Garden and the Chinese Garden, but there are 11 others. And over 15,000 different varieties of plants.

Well, today a vastly expanded version of the already exceptional Chinese Garden finally opens to the public. Here’s the press release about it:

After a nearly five-month postponement caused by the COVID-19 pandemic, The Huntington Library, Art Museum, and Botanical Gardens will open the outdoor areas of the highly anticipated expansion of its renowned Chinese Garden on Friday, Oct. 9, 2020. Visitors will be treated to 11.5 new acres of landscape, pavilions, and other features in Liu Fang Yuan 流芳園, the Garden of Flowing Fragrance. With this last phase of construction now complete, Liu Fang Yuan has expanded from its initial 3.5 acres to 15 acres, becoming one of the largest classical-style Chinese gardens in the world. The complex includes the 12 acres of the central garden, as well as an extensive bamboo grove on the garden’s western edge (to be completed in the next few months) and a conifer forest to the north.

Map of Chinese Garden, The Huntington
Map of the new garden. Ill.: © The Huntington

History of the Chinese Garden 

Lake of Reflected Fragrance, Chinese Garden, The Huntington
View of the Lake of Reflected Fragrance, showing some of the original features that opened in 2008 (l–r): the Pavilion of the Three Friends, the Jade Ribbon Bridge and the Hall of the Jade Camellia.  In the foreground is the Bridge of the Joy of Fish. Photo: Martha Benedict, © The Huntington

Inspired by the centuries-old Chinese tradition of private scholars’ gardens, Liu Fang Yuan (the Chinese Garden) made its debut in 2008 with eight pavilions linked by courtyards and walkways situated around a one-acre lake. In 2014, two new pavilions and a rock grotto were added. Groundbreaking on the garden’s final section began in August 2018. The following year, more than 50 Chinese artisans from the Suzhou Garden Development Co. spent six months at The Huntington carrying out specialized carpentry, masonry, and tile work for the traditional structures in the final phase. Their artisanship gives the garden its authenticity and beauty.

As with the earlier stages of the garden’s construction, this project has been an international partnership between Chinese and American architects, contractors, and craftspeople—all working together to ensure that the garden remains authentic to Chinese traditions of architecture and landscape design while meeting state and federal regulations for seismic safety and accessibility.

The total cost of this final phase of construction was approximately $24.6 million. This brings the combined total cost of the garden to about $54.6 million, all of which was raised from individual, corporate, and foundation gifts.

“We are delighted to be able to welcome visitors to explore these exquisite new features that further demonstrate the beauty and depth of Chinese cultural and landscape gardening traditions,” said Karen R. Lawrence, president of The Huntington. “The debut of these new sections of the Chinese Garden coincides with the conclusion of The Huntington’s yearlong Centennial Celebration, and symbolically opens a new chapter in the institution’s history.”

Gourd-shaped window, Chinese Garden, The Huntington
A gourd-shaped window frames a view and is an artful element in its own right. More than 50 artisans from Suzhou, China, provided the specialized carpentry, masonry and tile work that give the garden its authenticity and beauty. Photo: Aric Allen, © The Huntington

Indoor spaces within this expanded section of the Chinese Garden will open later. These include a new art gallery and a traditional scholar’s studio, as well as a casual restaurant. The inaugural exhibition in the art gallery, “A Garden of Words: The Calligraphy of Liu Fang Yuan,” is set to open in May 2021.

“The Chinese Garden has been more than two decades in the making, and the opening of this expanded section is the realization of the long-shared vision that countless individuals have worked toward: generous community donors, architects and designers from China and the United States, hardworking staff and volunteers, and many others,” said James Folsom, the Telleen/Jorgensen Director of the Botanical Gardens. “Together we have created a world-class attraction that not only celebrates historical landscape traditions but also embodies the contemporary ideals of international cooperation and cross-cultural exchange.”

Coast live oak, Chinese Garden, The Huntington
The design of the garden’s new features respects the existing landscape and safeguards mature trees like this coast live oak, Quercus agrifolia, estimated to be at least 300 years old. Photo: Aric Allen, © The Huntington

Timed entry tickets (purchased online in advance at are required for The Huntington as a whole, and visitors must comply with all mandated safety requirements, including a pre-entry symptom check, wearing face coverings and maintaining physical distancing while on the property.


The Stargazing Tower 望星樓 – Situated on the highest point in the garden at the southern end of the lake, this beautiful 527-sq.-ft. pavilion provides stunning views of the landscape, the distant mountains, and (with a bit of imagination) the universe beyond. The name pays homage to the Mount Wilson Observatory—visible from the tower—and to the work of astronomer Edwin Hubble. Hubble’s papers are part of the Library’s holdings in the history of science.

The Pavilion of Myriad Scenes, Chinese Garden, The Huntington
The Pavilion of Myriad Scenes, one of the architectural features within the Verdant Microcosm, the garden’s new penjing complex. Photo: Aric Allen, © The Huntington

The Verdant Microcosm 翠玲瓏 – This 17,900-sq.-ft. area on the western slope of the garden is designed for the study, creation, and display of penjing 盆景 (miniature potted landscapes, similar to Japanese bonsai). A complex of walled courtyards showcases dozens of examples of the penjing art form, as well as distinctive scholar’s rocks.

Reflections in the Stream and Fragrance of Orchids Pavilion 映水蘭香 – Shaded by mature California oaks near a gently flowing stream, this delicate 308-sq.-ft. pavilion is a place to pause, meditate, and be poetically inspired. The name recalls the legendary gathering of poets at the Orchid Pavilion in Shaoxing in 353, immortalized by the great calligrapher Wang Xizhi 王羲之 (ca. 303–361), who wrote the preface to the collected poems.

The Courtyard of Assembled Worthies, Chinese Garden, The Huntington
The Courtyard of Assembled Worthies in the expanded northern section of the garden, with the Flowery Brush Library at left. Photo: Aric Allen, © The Huntington

Courtyard of Assembled Worthies 集賢院 – Paved with intricate pebble mosaics, this expansive courtyard links the exciting Clear and Transcendent Pavilion on the north side of the lake—a frequent site of concerts and performances—with the new exhibition complex. Together, these features will serve as a center for future cultural programming.

INDOOR SPACES TO OPEN AT A LATER DATE: The art gallery, Studio for Lodging the Mind 寓意齋, is a 1,720-sq.-ft. climate- and light-controlled building at the northern end of the garden that will showcase changing exhibitions of Chinese artworks, both contemporary and historical. The gallery’s inaugural exhibition will feature Chinese calligraphy. Adjacent to the gallery is the Flowery Brush Library 筆花書房, a hall designed in the style of a scholar’s studio—a garden retreat traditionally used to create paintings and calligraphy. Also in this north section is a new casual restaurant with outdoor seating, known as the Pavilion Encircled by Jade 環翠閣. And a large open space overlooking the lake, the Terrace of Shared Delights 衆樂臺, will be used for banquets, festivals, and other gatherings.

The Flowery Brush Library, Chinese Garden, The Huntington
The Flowery Brush Library, one of the new structures in the expanded section of the Chinese Garden. The pavilion was designed in the style of a scholar’s studio—a garden retreat traditionally used for painting and calligraphy. Photo: Aric Allen, © The Huntington

“One of our primary goals in building Liu Fang Yuan was to make Chinese gardening traditions—including landscape design, architecture, art, and poetry—accessible to a wide audience of both Chinese and non-Chinese visitors,” said Phillip E. Bloom, the June and Simon K. C. Li Curator of the Chinese Garden and Director of the Center for East Asian Garden Studies. “The penjing complex, for example, provides a window into a centuries-old horticultural art form, and the new art gallery will anchor an exhibition and performance complex for which we are planning a robust slate of public programs, lectures, concerts, academic symposia, school programs, and other cultural offerings.”

So, the next time you’re in the Los Angeles, California area, you’ll know where to go!

Preparing Your Summer Cottage Garden for Winter


Just a bit of basic care will get your cottage garden ready for winter. Photo:

Around our homes, lawns, flower beds and vegetable gardens continue to grow until very late in the fall, so even in mid-October there are still plenty of plants still growing and blooming, even cold-tolerant vegetables you don’t have to hurry to harvest. But at the summer cottage, it’s often around mid-October that we close up shop for the season and return to town for the next few months. So, even as you unplug the appliances and pack up the leftover food to bring home, what do you have to do in the garden before closing the cottage?

In reality, relatively little. What’s great about a secondary home is that you can afford to only plant very hardy and maintenance-free plants and to have either no lawn or at least a less well-groomed one than in the city, and that greatly reduces the upkeep. 

Here are a few things you may have to do, though.

Lawn Care

Personally, I wouldn’t have a lawn at the cottage: it’s too much maintenance and aren’t cottages supposed to be for relaxing? But if you have one, and yes, many people do, know that its worst enemy in the fall is that layer of dead leaves that builds up on it, especially when it’s made up of large leaves like those of maple and oak. A dense layer of leaves can cut off light and air circulation, smothering lawn grasses. So, rake up what you can to give it some light.

Man using leaf blower to push leaves.
A leaf blower will quickly push the leaves off the lawn. Photo:

A leaf blower is faster than a lawn rake, though. Most give you two options. One is to can simply blow the leaves elsewhere, which is great if you have room for them. You could direct them into a forested area, for example, where they’ll decompose harmlessly. The other is the vacuum mode, which picks up and also shreds leaves. That will give you chopped leaves you can use in as a mulch for the flower bed or put into the compost.

A lawn mower with an attached leaf bag also makes an excellent “leaf picker-upper” for lawns. Use it to pick up and shred leaves you can then put to use elsewhere.

Finally, your lawn will likely still be growing at cottage-closing time, but its growth will be largely underground. Late in the season, its roots are still growing, but not the leaves, and that means you can give the lawn its final trim for the season. During summer, it’s always best to mow high, never lower than 3 inches (7.5 cm), as that gives a dense, healthier and more weed resistant lawn. The last mowing of the season is the one time you should mow low, only 2 inches (5 cm) from the ground. This will allow give the lawn better ventilation during the long winter months.

Flower Beds

Early fall flower bed
Flower beds pretty much take care of themselves in the fall. Photo:

There’s really not much to do there. You can just let them fend for themselves. 

True enough, in the old days, people used to cut back their perennials and pull out their annuals, but we know now that’s really not good for the garden. 

Cutting back perennials in the fall is now recognized as being bad for their health. It used to be thought that pruning them in the fall helped reduce insects and disease. We now know that it’s exactly the opposite: pruning weakens them and eliminates beneficial insects, so you end up with more diseases and insects the following year. In addition, the yellowing leaves of perennials are part of their winter protection plan: they evolved to stay on the plant and help protect the crown from the cold. So, just leave them be, as Ma Nature intended. 

You can, however, move and divide perennials in the fall if you have some empty spaces to fill.

As for annuals, though they’ll soon be dead if they aren’t already, they’re still useful in preventing erosion and also help shelter beneficial insects. Most will simply rot away over the winter, but if there are still traces of them in the spring, that’s when you could cut them to the ground. 

You can also cover flower beds, in and around the perennials and shrubs, with a thick layer (up to 4 inches/10 cm) of shredded fall leaves. This creates a mulch that will enrich the soil while helping protect the plants from the cold.

Do dig up any tender bulbs, such as gladiolus, dahlias and cannas, you planted last spring. They’re only hardy in very mild climates (zones 7 to 10, depending on the species). However, unless you heat your cottage in the winter, bring them back to the city with you rather than storing them in the cottage itself, as they can’t tolerate the freezing temperatures that generally reign in an unheated summer home over the winter. 

If you want to have flowers as soon as you reopen the cottage in the spring, plant hardy bulbs now. Since you don’t normally go to the chalet until mid-May, forget about the earliest bulbs like crocuses, hyacinths and snowdrops. Mid-season and late-season bulbs, like most tulips, narcissus and alliums, on the other hand, will be there to greet you.

Trees, Shrubs and Conifers

Shrubs wrapped in geotextile for the  winter.
No need to exaggerate with winter wrappings: properly chosen shrubs need no special care. Photo:

They need no special care for the winter. All the meticulous winter wrapping with burlap and geotextile that some city dwellers bestow on their woody plants at this season is mostly for show to impress their neighbors with how diligent and perfectionist they are. 

It is however true that if the road to the cottage will be maintained by a snowplow in the winter, harshly shoving piles of snow and gravel onto your lot, any shrubs, trees and evergreens in that sector can be seriously damaged. Rather than protecting them with complex wooden structures like you sometimes see, it’s better to dig up and move elsewhere any that got blasted the previous winter. 

The area immediately adjacent to the road should be reserved for perennials, as they’re dormant and underground by winter, so aren’t harmed by the action of snowplows.

In fact, the fall is an excellent season for planting or moving trees, shrubs and conifers. Don’t forget to mulch the base of recently transplanted woody plants with a good layer of shredded leaves to protect the roots from the cold, as they’ll still be quite fragile after the move.

Wrapping a young tree trunk with spiral tree bark guard.
How to install tree bark guard. Photo:

To protect the bark of young trees from voles (field mice), wrap the base of their trunk with tree bark guard, available in any garden center.

What About Roses? 

Hardy shrub roses are the best choices for the summer cottage because they’re very cold resistant and need no winter protection. If, on the other hand, you have roses that are not hardy locally, such as hybrid teas and grandifloras, solidly hardy only in zones 8–10, they’re exceptions and will need winter protection. Cover them with an 8-inch (20 cm) mound of soil taken from elsewhere in the flower bed and prune them back just enough to cover them with a rose cone. Punch holes into the cone near the top for better ventilation and use stakes, a brick or a large stone to hold it in place.

Or let them die and replace them with hardy roses next year!

Gardening Tools

Clean, sharpen and oil garden tools before storing them for the winter. And that includes the lawn mower. Also, if it’s gas powered, make sure to fill its tank to the brim with gasoline to prevent rust and condensation.

Garden hose outdoors in the snow
Garden hoses should at least be thoroughly drained before winter. Photo:

Turn off the outside tap and do your best to empty the garden hose of any water, as that might cause it to burst under the effect of freezing temperatures. Unless your cottage is heated, there’s no need to bring the hose indoors for the winter: frost will still get to it. 

So Little to Do

And that’s all! There isn’t really all that much you need to do to the garden around a summer cottage to prepare it for winter. Instead, focus on the cottage itself as well as the other accessories of summer living (garden furniture, boats, all-terrain vehicles, etc.). Preparing them properly for winter is quite enough without having to add unnecessary gardening chores!

How to Overwinter Tuberous Begonias


Tuberous begonias like these Nonstop begonias, don’t grow all year and will go fully dormant in the fall. Photo:

Tuberous begonias, mostly the large-flowered, double Begonia × tuberhybrida of which the ‘Nonstop’ series is perhaps the best known, or the smaller-flowered trailing B. boliviensis types, have a rather unique growth habit quite unlike other begonias (and there are literally thousands of non-tuberous begonias). They go dormant in the winter, losing leaves, stems and flowers, and then remain dormant for several months. They do this in all climates and whether they grow indoors or out. 

Tuberous begonias starting to turn yellow, indicating impending dormancy.
These tuberous begonias are not dying, they’re going dormant. Photo:

This is important to understand, as otherwise you might be quite upset when your beloved begonia seems to start to fall apart in the late fall or even throw it out, thinking it has died! 


In mild climates, ones where there is no frost, you can just let your tuberous begonia go dormant on its own, usually in late October or November in the Northern Hemisphere. 

In colder ones, though, it’s best to let the first frost cut it back. That way, its leaves will have had the longest possible period in which to store energy for the coming dormancy. This makes for a sort of forced dormancy brought on by the weather. A first frost won’t damage the tuber, still safely underground where it’s warmer than the air above, but don’t leave the tuber outdoors until the soil freezes or that will kill it.

Curing the Tubers

Tuberous begonias dried indoors, stems coming free.
As the tubers dry, the stems detach on their own. Photo:

In colder climates, once the foliage has been damaged by frost, you need to cure the tuber (harden it off). Dig up the entire plant including the tuber. Shake or knock most of the soil free and lay the plant in a warm dry area so it can dry out. This can take 2 or 3 weeks. When the tuber dries, the stems will detach on their own and can be removed and composted. After curing, shake off any remaining soil that comes free readily, but the tuber doesn’t have to be perfectly spotless.

If the tuber is in a pot, the treatment is much simpler. You can simply bring the pot indoors and let it dry as it is, removing the foliage when it comes free on its own. 

In climates with frost-free, dry winters, just cut off the foliage and leave the plant outdoors. It will sprout on its own come spring and you can then start watering it again. However, in mild climates where winter rains are current, you’ll still have to dig up the tuber (if it’s in the ground) and put it somewhere dry for the winter, either indoors or in a shed, or do the same with its pot if it’s growing in a container. 

💡Helpful Hint: Make sure you identify each tuber with a label as you bring it in. Even if you don’t know the cultivar name, you’ll likely want to at least know its color and form (upright, trailing, etc.). That way, you won’t mix up your tubers when planning your garden come spring. 

Winter Storage

Begonia tuber roughly cleaned of dirt.
When the tubers are dry, roughly clean them, removing most of the soil. Photo: Richard Jackson

You need a protected, dry location in which to store your tubers for the winter. Contrary to popular belief, though, it doesn’t have to be that cold. Tuberous begonias are tropical plants and, even when dormant, might find the near-freezing temperature inside some cold rooms too chilly. Temperatures between 40 and 55 °F (5 to 12 °C) are quite adequate. 

You don’t have a cool spot where you can store your tubers? You can easily store them at room temperature too. However, warmer air means there will be more evaporation and thus some dehydration. That means you’ll have to take an extra step and moisten them occasionally through the winter, just spray them lightly with water every month or so (see below).

Traditionally, tubers are stored in the dark, but in fact, that really isn’t necessary. They’ll do just as well in a brightly lit spot as a dark one. 

Begonia tubers ready for storage.
Tubers dried and cured, ready to be stored. Photo: Carrie’s Gardening Channel

You can store bare tubers in a cardboard box, placing them on a layer of peat moss, vermiculite or sawdust, then covering with additional peat, vermiculite or sawdust, or wrap them in paper. I put mine in individual paper bags, stapling the label to the outside, then pack them together in a box. That way if any insect or disease has followed one tuber indoors, it can’t spread to the others.

As for tubers stored in pots, just pile the pots up somewhere one on top of the other. 

Monthly Inspection

It’s wise to inspect the tubers monthly. Remove any that show signs of rot. If the tuber seems to be shrinking and wrinkling, just spray it lightly with water and it will plump up again. 

Tubers stored in pots aren’t as easy to inspect but, being in soil, they’re somewhat protected anyway, so don’t tend to dry out excessively like loose tubers sometimes can. However, you may still want to sniff the pots to detect rotting tubers. They’ll smell like a rotting potato.

Come Spring

Begonia tubers sprouting in the spring.
The appearance of fresh sprouts tells you the tubers are ready to start a new season. Photo:

Tuberous begonias conveniently tell you when it is time to start a new growth cycle. The tubers start to sprout all on their own towards the end of the winter. There’s no need rush and immediately plant them at the first appearance of sprouts: they do start to grow, but then stop and wait for appropriate conditions before going further.

What you’ll want to do is to wait until about 6 to 8 weeks before the planting-out date in your area, then repot the tuber (if it was stored bare) or just bring out the pot and start gently watering again. To help the plant on the way to summer bloom, place it in well-lit spot indoors at normal room temperatures. 

In no time, your begonia will be in full leaf and shortly after, in full bloom as well, just what it takes to properly launch your new flowering season.