Thought of the Day



To forget how to dig the earth and tend to the soil is to forget ourselves.

     Mahatma Gandhi 


Why I Just Love Dwarf Conifers


A garden dominated by dwarf conifers. Source:

I like making gardening easy, so dwarf conifers fit me like a glove. Imagine! Once the plant is established (so, after the first year), there is no need for pruning, fertilizing, winter protection or even, in most cases, watering … at least, unless there is a really bad drought. Really, they don’t make plants any easier: they’re just the thing for the laidback gardener!

True enough, gardeners who are focused on blooms are going to find them a bit dull, because conifers simply don’t have striking flowers. In fact, in most cases, the flowers are so discreet that they literally go unnoticed! But flowers aren’t everything, and yearlong foliage is hard to beat. After all, how many flowering plants can offer non-stop beauty 12 months a year? And dwarf conifers come in such a wide-enough range of colors, textures and shapes (pyramidal, oval, columnar, flared, rounded, mounded, etc.) that any decent garden designer could create striking gardens using them alone!

What Is a Dwarf Conifer?

Very few conifers are natural dwarfs. Most dwarf conifers come about as mutations, when a normal branch on a normal tree suddenly produces a section with very compact growth, often with shorter needles. This type of mutation often forms a clump of branches, a phenomenon known as a witch’s broom. If you take a cutting or graft a branch from a witch’s broom, usually the new plant keeps its compact growth habit. Bingo! You now have a dwarf conifer.

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Some of the huge conifers in the Pinetum at Bodnant Gardens, Conwy, Wales are dwarf conifers planted in the 1870s. Source: naturalistsnotebook

However, the term “dwarf conifer,” although the accepted term in horticulture, was really not well chosen. I would have rather called these plants “slow-growing conifers,” because any conifer, even a so-called dwarf one, will continue to grow all its life. So, eventually, even the smallest of the dwarf evergreens will become humungous over time. I’ve seen a “dwarf” conifer that I was told was 65 feet (20 m) tall (no, I didn’t measure it myself!)! Admittedly, it was believed to be well over one hundred years old, but still, that gives you an idea that dwarf conifers do grow and perhaps faster than you think.

Conifer Size Categories

The American Conifer Society developed four size categories for conifers, according to their growth rate, and this very useful information is being shared by more and more nurseries.

Miniature Conifer: grows less than 1 inch (2.5 cm) per year, so a 10-year old specimen could still be under 1 foot (30 cm) in height and spread.

Dwarf Conifer: grows 1 to 6 inches (2.5 to 15 cm) per year. That means some might be 5 feet tall or wide after 10 years … possibly less dwarf than you had hoped.

Intermediate Conifer: grows 6 to 12 inches (15 to 30 cm) per year.

Large Conifer: grows by more than 12 inches (30 cm) per year.

For small gardens and intimate corners, therefore, prefer miniature or dwarf conifers.

Understanding Conifer Labels


All dwarf conifers look cute when you buy them, but how will they look in 10 years? Or 20 years?  Source:

Did you know that when you buy a dwarf conifer, the dimensions listed don’t refer to its maximum size, but rather its dimensions when it reaches 10 years old? It will not just reach that size and stop growing, but will keep on at the same pace. This convention, adopted by many conifer growers, is not well-known to amateur gardeners, who assume that measurements they see on the label are maximums and so are surprised—if not stunned!—to see their “dwarf conifer” engulf their entire flower bed over time.

For example, a dwarf mugo pine (Pinus mugo mughus) whose dimensions are listed as something like 3 feet (1 m) in height by 5 feet (1.5 m) in diameter will reach that at about 10 years of age and will certainly not be very dwarf in 20 years when it will measure 6 feet (2 m) in height and 10 feet (3 m) in diameter! And imagine its size in 40 years!

Laidback Gardening Tip


This miniature conifer garden looks fine now, but it’s very overcrowded. Already some varieties are encroaching on others and things will only get worse over time. You have to give dwarf conifers considerable space if you want their effect to last. Source:

When you’re planting a dwarf or miniature conifer, mentally double the dimensions on the label or in the catalog, then place the plant according to those calculations. In other words, set each tiny plant at quite a distance from its neighbor! Then cover the soil with thick mulch to prevent weeds as it slowly grows and fills in. That way you’ll have about 20 years of beauty with little to no maintenance.

Dwarf Conifers Often Age Badly

Unless you have a lot of room, it isn’t easy to recuperate an overgrown conifer and, in fact, in most cases, it’s probably impossible: most of them simply do not respond well to rejuvenation pruning. So, after 20 years of lying back and watching yours grow and thrive, get out of your hammock and put a bit elbow grease into removing it. Then replace it with another dwarf conifer. That will give you another 20 years of peace!

Growing Dwarf Conifers

I can only give you very vague information about growing dwarf conifers. That’s because there are so many different varieties, each with their own preferences. For example, when it comes to climate, some thrive in the tropics, others in the Arctic and some do just fine under desert conditions while others prefer rainforests. That gives you some idea about just how widely their needs can differ!

Even some, a few generalities do apply.

For example, most prefer full sun and will tolerate partial shade. There are also a few shade-tolerant conifers, such as yew and hemlock.

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Most conifers need well-drained soil … but the bald cypress (Taxodium distichum) is an exception and will grow with its roots in water. And yes, there are dwarf varieties of this species. Source: Kej605, Wikimedia Commons.

Most conifers prefer well-drained soils, although there are a few that will grow in soggy ones! Most do fine in acid soil, but none require acid soil. There are also conifers tolerant of alkaline soils (some junipers and yews, for example), but again, none require such soil.

Watering needs of most conifers are fairly modest … once they’re established, at least. The first year after planting, it would be wise to keep their soil on the moist side until their roots develop. Thereafter, you’d only need to consider watering them in periods of extreme drought. If the fall is dry, though, water them until the ground freezes, otherwise their needles may dry out and “burn” during the winter.

(Note that container-grown conifers are more dependent on watering than those growing in the ground and should be watered regularly and thoroughly as soon as their soil begins to dry out.)

Few conifers tolerate salt spray (white spruce [Picea glauca] and blue spruce [Picea pungens] are among the few exceptions), so it’s not wise to plant conifers too close to bodies of salt water or near roads treated with de-icing products in winter. Nor should you plant conifers in the path of snowblowers that shoot out snow and ice crystals that tear off needles, bark and buds.

Of course, always choose conifers adapted to your local hardiness zone. The hardiness zone of the variety is usually listed on the label. Basically, choose plants adapted to your zone or colder ones (ones with lower numbers). If you live in zone 6, for example, choose conifers adapted to zones 1, 2, 3, 4, 5 or 6, but not 7. In zone 5, go for zones 1, 2, 3, 4 and 5, but not 6. Etc.

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This abnormal growth spring from a dwarf spruce is a reversion. Prune it out or it will take over the plant. Source: Ragesoss, Wikimedia Commons

Normally, if you have chosen the right dwarf conifer for your location, no pruning will be needed. On the other hand, sometimes dwarf conifers produce a reversion, a stem that returns to the normal growth pattern of the species, i.e. a much longer distance between nodes. If you leave the reverted stem on the plant, it will grow faster than the rest and take over, destroying your plant’s symmetry, so just prune it off.

But shouldn’t you be fertilizing your dwarf conifer? Well, first remember that you want it to stay small. Fertilizer can stimulate longer branches and you don’t want that. Plus, even normal-sized conifers usually get along fine without fertilizer. (Those specialized conifer fertilizers you find on the market are mostly there to give anxious gardeners the impression they’re doing something useful for their plants.) Unless the soil you’re growing your conifer in is extremely poor, it will take care of its own mineral needs.


You might want to consider a bit of winter protection the first year. Source:

If you chose a conifer adapted to your growing conditions, no water protection should be needed. And indeed, one of the reasons we plant dwarf conifers is because they are attractive year-round, hardly the case if you wrap them for the winter! However, it may be useful to protect yours from the drying effects of the wind for the first winter. No need to wrap them up like a mummy, though. Just install a temporary screen (a piece of geotextile or jute stretched between two stakes, for example) between the plant and prevailing wind at the end of autumn. In following years, no protection will be necessary.

Container Conifers


You can make a lovely mini landscape in a container with the smallest conifers. Source:

Dwarf conifers—and especially miniature ones—also make excellent container garden subjects for decks, balconies or rooftop gardens. But be sure to choose an extra-hardy cultivar, as cold penetrates more deeply into the soil of potted plants than it would in the ground. So, prefer a variety hardy to at least one zone colder than your zone. Gardeners in Zone 6, for example, should consider conifers for zones 1, 2, 3, 4 or 5 for container culture rather than zone 6; those of zone 5, conifers for zones 1, 2, 3 and 4, but not 5, etc.

There you go: colorful dwarf conifers may be just what you need to give your landscape a bit of pizzazz in all seasons while you just relax and let them grow!20180718A

A New Pest Practically in My Own Backyard!

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Damaged goat’s beard leaves with two sawfly larvae visible. Source: Julie Nadeau

No one wants to hear about a new insect pest. There are already so many of them and it seems new ones appear every year. Well, sorry to have to tell you, but here’s one more, especially interesting to me because I (sort of) helped discover it.

Three years ago, a reader from Quebec City, Canada (where I live), sent me a photo of the damage done to her goat’s beard (Aruncus dioicus), a popular perennial reputed to be particularly easy to grow and free of insects and diseases. Certainly, I’ve grown it for years and have never seen a “bug” touch it. But on hers, the leaves were skeletonized, with only veins remaining. She described the predator as being a little green caterpillar.

I was baffled. I’d never heard of a goat’s beard suffering an insect attack, at least not in North America. On the other hand, considering the damage (I had her send me a photo), the fact that it only fed on goat’s beard and the description of the insect, it really sounded a lot like the goat’s beard sawfly (Nematus spiraeae). Yet this insect is strictly European in distribution.

I explained to the reader that I wasn’t sure, but it sure sounded like sawfly damage and explained what to do about it. Still, I had my doubts. What insect was it really?

A Scientific Confirmation

I kept getting emails about this pest, all very local, both in 2016 and 2017 and again this year. So I checked the Internet again a few times … and last week, eureka! I discovered the pest had been officially identified.


This report identifies the culprit. Source:

The report A Palearctic Sawfly on Aruncus (Rosaceae) New to North America, by Joseph Moisan-De Serres of the Quebec Department of Agriculture, Fisheries and Food and David R. Smith, Department of US Agriculture, was published in August 2017. It reports the discovery of this European insect in a private garden in Stoneham, Quebec (just north of Quebec City) in 2016. According to the owner of the garden, the insect had been present for “four or five years,” so since 2011 or 2012. The report makes no suggestion as to how the pest got from Europe to Canada.

Potential Distribution

How far will this insect spread?

For the moment, it seems to be confined to the Quebec City region in eastern Canada, but is spreading locally. Given that goat’s beard is not only native throughout much of North America* (other than in the more arid Prairie states and provinces), but is also widely grown as an ornamental throughout temperate areas of the continent (even in the Prairies!), the sawfly can readily find its host plant just about everywhere and it’s therefore probable it will expand its range over time, likely throughout North America.

*Goat’s beard (Aruncus dioicus) is native throughout the temperate Northern Hemisphere, thus not only North America, but Europe and Asia as well.

So, here’s what to be prepared for:

Description and Life Cycle

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Adult goat’s beard sawfly. Source: Joseph Moisan-De Serres, DP,  Quebec Department of Agriculture, Fisheries and Food

The goat’s beard sawfly (N. spiraeae) is a rather svelte flying insect with black to brown head and a yellowish abdomen. It’s about 5 to 6 mm long. Despite its wasplike narrow waist and long antennae, it’s a sawfly, perhaps distantly related to ants and wasps, but not a true wasp and no, it will not sting.

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Goat’s beard sawfly larva. Source: Joseph Moisan-De Serres, DP,  Quebec Department of Agriculture, Fisheries and Food

The larva looks much like a caterpillar, but that term applies strictly to butterfly and moth larvae, so it is sometimes called a false caterpillar. It’s light green and somewhat translucent with a greenish to brown head. It can measure up to 20 mm in length.

The female reproduces by parthenogenesis (without fertilization) and in fact, no male of this species has ever been found. It emerges in late spring and lays small white eggs under goat’s beard leaves, its exclusive host. Larvae, very gregarious, feed on the tissues between the veins of the leaves. After a few weeks, they drop to the ground, dig in, weave a shelter of silk and become pupae, then remain quiescent for about a month. A second cycle then begins. In mild climates, there is often a third generation in early fall. The larvae of the year’s final generation drop to the ground in the fall and overwinter underground as larvae, becoming pupae only in the spring. Then the cycle starts all over.

Reducing Damage

Goat’s beard sawfly populations are very irregular: there are years when you’ll scarcely notice the damage and others where the whole plant is defoliated.

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Goat’s beard sawfly larvae are gregarious, so you’ll likely see many on the same part of the plant. Source: Joseph Moisan-De Serres, DP,  Quebec Department of Agriculture, Fisheries and Food

The easiest and most effective way of controlling them is to keep an eye open for the larvae, then when they appear in early summer, knock them off the plant into a bowl of soapy water. Since they are gregarious, at least they tend to concentrate on the same part of the plant, making harvesting easier.

Or spray with a pyrethrum-based insecticide, preferably in the evening. Although it’s an organic insecticide, it has a broad spectrum and can therefore harm bees and other pollinating insects, so avoid applying it when your goat’s beard is in bloom. Note that although the pyrethrum treatment works well on young sawflies, more mature ones seem to be fairly resistant to insecticides.

Note that you would be wasting your time applying BTK (Bacillus thuringiensis kurstaki) to control goat’s beard sawfly. This popular organic pesticide is only useful for controlling true caterpillars, not false ones!

Well, let’s all hope that the goat’s beard sawfly doesn’t spread any further, but I’d be surprised if it didn’t. Otherwise, it will end up knocking yet one more plant—goat’s beard—off the list of the truly easy perennials anyone can grow!

If you find sawflies on your goat’s beard plants, please share the information with Joseph Moisan-De Serres of the Quebec Plant Protection Expert and Diagnostic Laboratory. He’s trying to track the progress of this new invader. He can be reached at Julie Nadeau.jpg

A Fast and Easy Green Carpet!


English ivy (Hedera helix) used as a ground cover. Source:

Almost any climbing plant (vine) will make an excellent groundcover plant if you place it where there is nothing it can climb or cling to (tree, arbor, trellis, wall, etc.). And climbers cover a lot of space very quickly, much faster than more typical groundcover plants, meaning you need to buy fewer plants. For example, a single Virginia creeper plant can easily cover 100 square feet (10 m2) in only 2 years!

If climbers grown as creepers start to go too far, just trim their extremities… and this is doubly beneficial in that it will encourage them to fill in faster.

Here are few climbing plants you might want to consider for use as groundcovers:

Plants for Cold Climates

  1. Akebia (Akebia spp.)
  2. Boston ivy (Parthenocissus tricuspidata)
  3. Clematis (Clematis spp.)
  4. Climbing honeysuckle (Loniceraspp.)
  5. Climbing hydrangea (Hydrangea petiolaris)
  6. Climbing or rambling rose (Rosa spp.)
  7. Dutchman’s pipe (Aristolochia spp.)
  8. English ivy (Hedera helix)
  9. Everlasting pea (Lathyrus latifolius)
  10. Grapevine (Vitis spp.)
  11. Trumpetcreeper (Campsis spp.)
  12. Virginia creeper (Parthenocissus quinquefolia)
  13. Wintercreeper (Euonymus fortunei)

Plants for Moderate to Tropical Climates*


Morning glories (here Ipomoea tricolor ‘Heavenly Blue’) make wonderful, fast-growing groundcovers. Source:

  1. Black-eyed Susan vine (Thunbergia alata)
  2. Blue pea (Clitoria terneata)
  3. Blue trumpet vine (Thunbergia grandiflora)
  4. Bougainvillea (Bougainvillea spp.)
  5. Clerodendrum (Clerodendrum spp.)
  6. Coral vine (Antigonon leptopus)
  7. Hyacinth bean (Lablab purpureus, formerly Dolichos lablab)
  8. Jasmine (Jasminum spp.)
  9. Mandevilla or dipladenia (Mandevilla spp.)
  10. Morning glory (Ipomoea spp.)
  11. Passion flower (Passiflora spp.)
  12. Rangoon creeper (Quisqualis spp.)
  13. Scarlet runner bean (Phaseolus coccineus)
  14. Star jasmine (Trachelospermum spp.)
*Many of these plants can be used as annual groundcovers in colder climates.

How to Hybridize Your Own Tomato

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Anybody can create new tomatoes through hybridization. Source:, &, montage:

When it comes to pollination, domestic tomatoes (Solanum lycopersicum) are curious plants. The flower is essentially closed, as the pistil (female part) is shorter than the stamens (male parts) that form a protective cone or tube around it.

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Structure of a tomato flower. Note the hidden stigma inside the staminal cone at the center of the tomato flower. Source:, montage:

That means the flower does not readily accept pollen from outside sources. That’s why it’s so easy to maintain heritage tomato lines: unlike almost any other vegetable, you don’t have to be too concerned about cross-pollination: pollen from another variety is unlikely to arrive and create an unwanted hybrid with mixed genes.


A wild tomato flower (left) has an exerted stigma, available to pollinating insects. No stigma is visible in the domestic tomato flower (right). It’s hidden inside the staminal cone where insects can’t reach it. Source:, montage:

This wasn’t always the case. Wild tomatoes do cross readily, with a stigma that extends beyond the staminal cone, a structure designed to permit cross-pollination. But about 1500 years ago, undoubtedly somewhere in the Andes, a mutation with a short pistil appeared, so the stigma (at the tip of the pistil) remained inside the staminal cone, out of reach of pollinators. Clearly gardeners of the time appreciated the innovation, as once they developed bigger, juicier, tastier tomatoes, they could maintain them without fear their plant’s good traits would be overwhelmed by wild tomato genes. Soon, they grew them exclusively and self-pollination became the norm for domestic tomatoes.


Bumblebees vibrate to release pollen. Source:

Even so, tomatoes still need bees*, preferably bumblebees, whose vibrations release the pollen grains from the stamens so they can fall on the stigma. (This is called buzz pollination or sonication.) However, the pollen inevitably falls on the stigma of the same plant, resulting in self-pollination.

*Sometimes wind will pollinate tomatoes in the absence of bees.

Breaking the Rules

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To develop giant tomatoes like this ‘Giant Monster’ (‘Belgian Giant’), hybridizers crossed large strains of tomatoes, then repeatedly selected for size over several generations. (Tomato generations, that is!) Source: Jack Seeds

To hybridize tomatoes, in other words, cross one tomato variety with another, you have to break the rules. You’ll have cut open the flower to move the pollen from one flower to the stigma of another.

Let’s say you have a favorite tomato with outstanding flavor and great disease resistance, but it’s a weak grower and none too productive. Yet another tomato you grow is ultra-vigorous with a massive production of … not-so-tasty fruits and unfortunately, it’s terribly subject to disease. You could try crossing the two and attempt to create the vigorous, tasty, productive, disease-resistant tomato of your dreams.

Here’s how:

Gather Your Tools

You’ll need:

• small labels you can attach to the flowers (jewelry tags are perfect!);
• a pen or pencil;
• forceps or fine-tipped tweezers;
• a fine artist brush;
• two different tomato varieties
• reading glasses (for most of us).

Step by Step

This is very delicate work and at first you may end up damaging the flowers you’re working with. Take it slowly and be patient. You’ll soon get it!

You have to be growing the two tomatoes you intend to cross and both must be in bloom. Also, choose a period when there will be a few sunny days in a row. Tomato flowers won’t always mature in rainy weather.


Make sure you label your crosses. Source:, montage:

1. Start by writing the names of the parents (and the date if you want) on the label. You’ll need one label per intended cross.

2. On the plant you decide will bear the hybrid fruit (the female parent), choose a flower bud at the right stage. It should be well developed and turning yellow, but not yet open. If it’s it already open, it’s too late and will likely have been fertilized by its own pollen.

3. Remove all other flowers from the cluster to prevent accidental pollen transfer from another bloom on the same plant.

4. Remove the petals with the forceps or tweezers. They’re easy to remove.

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After removing the petals, carefully pull off the staminal cone. Source: &

5. You now have to emasculate the flower (remove its male parts). This is extremely delicate and I found it took me about 5 tries before I could do it without damaging the pistil (the female part). I found after practice that if I carefully grasped the staminal cone with forceps and pulled straight forward, it would generally come off, although at first I was only able to remove the stamens by pulling them free one by one (very tedious!).

6. Repeat with 4 or 5 other flowers to be sure of success.

7. Attach the label to the pedicel (stem) of the flower so you can better find it the next day, as the pistil will not yet be receptive. You’ll have to wait 24 to 36 hours before pollinating it.

There is no need to bag the flower: without petals to attract them, insects will not visit the pistil.

8. The next day, harvest a fully mature (open) flower from the male parent.

9. Open its staminal cone lengthwise, inserting the forceps into one of the slits in its side and forcing it apart.

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Lightly run the tip of the brush from the bottom to the top of a stamen to pick up pollen. Source:, montage:

10. Run the brush against the inside of a stamen, starting at the base and dragging it upwards to pick up pollen. You’ll see white powder (the pollen) form on the tip of the brush.

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Apply pollen to the stigma. Source: &

11. Apply the pollen to the emasculated flower, at the very tip of its pistil, the part called the stigma, which should be a bit sticky at this point. Apply enough to cover the stigma in white pollen.

12. Repeat about 12 hours later in case the stigma was not receptive the first time.

You’ll likely want to make several crosses, as not every one “takes.” You’ll know it has a few days later when the ovary at the flower’s base begins to expand and a fruit starts to form.

Testing Your Results

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Source: &, montage:

When the fruit you pollinated is fully mature, extract the seeds, then clean and dry them, storing them in a paper envelope with the label attached.

In the spring, sow the seeds about 6–8 weeks before you plan to plant the tomatoes out. As the plants grow and produce fruit, choose a ripe one from the plant that best meets your goals (productive, tasty, vigorous, disease-resistant, etc.) and keep its seeds. The following year, sow them, then again collect seeds from the best plant. And repeat the following year, and the following year. And so on.

By annually choosing the plant closest to your expectations, you’ll eventually obtain a stable line (although that can take 6 years, sometimes even more!): one where the plants meet your needs and are essentially identical. Congratulations! You’ve just created a brand new tomato variety! You can now give it the name of your choice and share it with the world.

Not What You Hoped For?


So, maybe your tomato isn’t the most beautiful one in town, but at least it’s yours! Source:

You didn’t get exactly the results you hoped for? That’s not unusual. Some tomatoes just don’t give good results when you cross them. Try again with other parents, remembering you’re doing this for the pleasure of it.

After all, even professional tomato hybridizers, who have an excellent grasp of tomato genetics, can spend a decade or more developing tomatoes that exactly match their goals.

Even so, almost all those heritage tomatoes that abound on the market today were developed by home gardeners: ‘Brandywine’, ‘Aunt Gertie’s Gold’ and ‘San Marzano’ are just a few examples among literally hundreds. And there’s the famous ‘Mortgage Lifter’ developed by the American M.C. Byles, that brought in enough money to pay off his $6000 mortgage back in the 1940s. That proves that some home gardeners have hit the jackpot in the past and there’s no reason you couldn’t as well.

Best of luck!20180715A, &

Garden Myth: Plants Grow Better with Coca-Cola


Is watering plants with soft drinks really good for them? Source: & Montage:

No, Coca-Cola is not good for plants … and you can substitute the soft drink of your choice for Coca-Cola in that statement. Where this strange belief comes from, I have no idea, but it’s widely repeated on the Internet.

Soft drinks are essentially carbonated water with lots and lots of added sugar. Carbonated water in itself is not harmful to plants and could even be good for them under some circumstances, but that’s not the case for sugar or, should I say, sugars, as various kinds of them are used in soft drinks: glucose, fructose, sucrose, etc.

True enough, plants produce their own sugars and use them for their growth, but they can’t absorb them: the molecules are far too complex for roots to take in. And when you break down sugars, they give only products plants are already getting from air and rainwater: hydrogen, oxygen and carbon. So where’s the benefit?

Adding too much sugar to soil can lead to dehydration, as water will be pulled out of the plant’s roots to dilute any concentration of sugar (this is due to osmosis, something many of you probably vaguely remember from school). Plus the bacteria and fungi that break down sugars are not usually ones that are beneficial to plants in any way and may become so numerous they “gum up” the soil, preventing air and water circulation. Also, many sugar-loving soil microbes are actually harmful to plants, notably causing root rot.

So, watering plants with soft drinks does no particular good and can possibly harm them.

I suggest just watering plants with … water! It’s cheaper and better for them.

With Container Plants, Double Up on Fertilizer


To thrive, container gardens need lots of water… and fertilizer! Source:

If you want outstanding container flower gardens or abundant, tasty vegetables in pots, you have to both water and fertilize them. And the latter can present a problem.

Container plants dry out much more quickly than in-ground plants, a fact that is readily visible, as the leaves wilt quite dramatically, and the need to water more frequently is well understood by most gardeners, who therefore water them more frequently. Check! But what gardeners often fail to understand is that plants grown in containers (flower boxes, hanging baskets, planters, etc.) also need more minerals (fertilizer) than plants growing in the ground. That’s because the minerals are regularly leached out by rainfall and watering.

What is Leaching?

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Rain and watering move soluble minerals out of the root zone, but then they move back up as the soil dries. In containers, minerals just drain away! Source: &, montage:

When rain falls on a plant growing in the ground (or when you water it), minerals present in the soil tend to percolate downward as the water does. However, when the rain stops and the soil nearer to the surface starts to dry out, water is “pulled” back up from below due to capillary action … and minerals follow. The result is that minerals tend to stay more or less within the plant’s root zone. Perfect!

When you water a plant growing in a pot or it rains, excess water drains out of the pot … and so do its minerals. They can’t move back up as the soil dries out. And since you water container plants much more often than garden plants, often several times a week, this repeated leaching impoverishes the soil that the container plants grow in, leading to weak, lackluster growth and decreased flowering and yields.

The Two Fertilizer Solution

Many gardeners have found that the easiest way of keeping their container plants productive is to combine two fertilizer strategies.

First, mix in a slow-release fertilizer (usually good for at least three months use) into the potting medium at planting time in spring, according to the label (and also mycorrhizal fungi, very efficient at helping plant roots collect both minerals and water). Fertilizer spikes and tablets are also slow-release. If you didn’t do so in spring, you can at any time during the summer (by fall, though, it’s probably too late for slow-release fertilizers to be of much use, at least in climates where plants stop growing for the winter).


Simply add soluble fertilizer to the watering can when you water. Source:

Then also fertilize with a soluble fertilizer, adding it to your watering can and applying each time you water your plants*. This is called the constant fertilization method.

*During periods of extreme heat, it may be wise to stop fertilizing for a while, especially if your plants react by ceasing to grow. You can restart your regular fertilizing method when temperatures return to normal and plant growth is relaunched.

Hose-end sprayer. Source:

If you water using a hose, you’ll find a variety of hose-end sprayers to which you can add soluble fertilizer.

Dilute Accordingly

Most soluble fertilizers are labeled for use once per month, but it’s easier to remember when it’s time to fertilize if you add them at each watering: then it becomes part of your routine. However, it’s very important to dilute the fertilizer accordingly: typically, you’d apply them at one quarter to one eighth of the recommended monthly dose. And the dose, of course, will vary widely, according to the brand of fertilizer you use. (Hint: read the label!)

Organic or Synthetic: You Choose

Note that there are both organic and synthetic slow-release fertilizers and organic and synthetic soluble fertilizers. Personally, I prefer the organic option and use a slow-release organic one, such as chicken manure, early in the season, then complete with liquid seaweed fertilizer throughout the season.

Whatever method you choose, do keep in mind that container plants will need more minerals than your garden plants … and react accordingly!20180713A