How to Overwinter a Bougainvillea Indoors

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Bougainvillea outdoors over the summer. Photo :

Question: I have a beautiful bougainvillea that has bloomed all summer. I was told that I could keep it indoors in the winter, but how?

Maude Archibald

Answer: The bougainvillea (Bougainvillea spp.) is a spiny climbing subtropical shrub that can bloom on and on for months, even all year long under very good conditions. There are more than 300 cultivars with different colors of bracts, most of which are complex hybrids between different species. You’ll see giant specimens covering entire walls in Mediterranean and tropical climates, but also potted bougainvilleas of a much smaller size (thanks to judicious pruning) sold in pots and baskets as a summer annual in colder areas.

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Louis-Antoine de Bougainville

The bougainvillea was named in honor of Count Louis-Antoine de Bougainville, an 18th century French aristocrat, navigator and explorer.

What a bougainvillea likes is full tropical sun, moderate watering (unlike most plants, it does better if you keep it on the dry side than evenly moist) and regular fertilization during its growing period. In regions with mild winters (zones 9 to 11), where it can be planted outdoors, that can sometimes be all year, but in more Mediterranean climates it will go semi-dormant and stop blooming over the winter. In temperate climates, you either have to grow it as an annual and let it die in the fall, or shelter it indoors over the winter … and keeping it alive it indoors during the dark days of winter is the subject of this article.

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True bougainvillea flowers surrounded by colorful papery bracts.. Photo : Max Pixel

The true “flowers” of the bougainvillea are small, fairly ephemeral white or pale yellow trumpets surrounded by three papery bracts (double bougainvilleas have more bracts). It’s these bracts in red, purple, yellow, orange and white—and that last for months!— that give the plant its festive appearance.

Keeping It Alive

Make sure you bring your bougainvillea indoors before frost hits. True enough, you’ll read that it’s able to tolerate some frost, but that’s when it’s growing in the ground … and even then, the damage can be severe. In pots, where frost can penetrate right through the root ball in no time, a serious cold snap can kill it outright.

There are two ways to keep a bougainvillea alive indoors over the winter: keeping it growing as a houseplant or forcing it into dormancy.

1. As a Houseplant

Place the plant in the sunniest spot possible, preferably in front of a large south-facing window or, better yet, in a moderately heated greenhouse or veranda with light coming from several sides. Even under these conditions, the plant will probably lose many of its leaves when you bring it in, as lighting indoors is always less than outdoors.

Things will only get worse as autumn gives way to winter and days become shorter and darker. In temperate regions, winter light is rarely sufficient for its taste. Good atmospheric moisture may help the plant to retain a few more leaves though.

Ideally, you’d lower the temperature as well to 45 °F or 50 °F (8 °C or 10 °C), but that’s not always possible in many homes. Fortunately, it will put up with room temperatures if it has too.

Your goal during the fall and winter is just to keep your bougainvillea alive, not to stimulate growth, so water very modestly, letting the soil dry out considerably before watering again. Nor should you fertilize in fall or winter: that will only stimulate weak growth you’ll have to prune off later.

2. Force It Into Dormancy


Bougainvillée en dormance. Photo :

Dormancy is not a normal state for bougainvilleas. In the wild, they do best where they can grow at least a bit at all times. Still, they’ll adapt to it if necessary.

To initiate dormancy, place the plant in a cool basement, a heated garage or any other cold but frost-free spot. No light is needed: the plant will be dormant, after all. Water only enough so that the root ball doesn’t dry out completely, perhaps once or twice a month. The plant will lose all its leaves, but that doesn’t mean it’s dead.

Back to Life in Spring

With the return of longer days in March, it’s time to wake your bougainvillea up. If possible, place the plant in a sunny room and start giving it better care, especially more frequent waterings. Start fertilizing it too (any fertilizer will do), lightly at first, at about one eighth of the recommend rate, then more as it puts on more growth. The idea at this point is to give it a head start on summer.

This is also the time for a bit of pruning. Since bougainvilleas bloom on new wood, you can cut them back quite severely and that should stimulate the growth of more branches and therefore more bloom in the months to come. Besides, who has the space to allow a potted plant to produce branches 10 feet (3 m) long? However, the downside to pruning is that it will also delay blooming. A good compromise is to cut the branches back by about a third. (Note too that, during the summer months, you should also prune back any stems that are getting too long.)

If you want to repot, spring is also the right season. Note that bougainvilleas bloom best when they’re a bit underpotted … but they’re fast-growing plants: after 2 or 3 years, you’ll have no choice but to repot it.

A Summer Outdoors

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Bougainvillea bracts come in some pretty flamboyant colors!. Photo : adrien0, Pixabay

As soon as the risk of frost is gone, gradually acclimatize the plant to outdoor conditions. A site in full sun is ideal. And remember to water and fertilize regularly.

Remember that bougainvilleas really aren’t good houseplants, that you only bring them indoors to keep them alive until the following summer. It’s outdoors under the intense summer sun that bougainvilleas truly strut their stuff! So be prepared to accept a rather discouraging winter appearance as the price to pay for beautiful summer blooms!20170924A ‘Elsbeth_ HortiCom



Pears Don’t Ripen on the Tree


Ripe or not ripe? With pears, you can’t tell by looking or even by touching! Photo:

Unlike apples, cherries and in fact the vast majority of other fruits, the European pear, also known as the common pear, (Pyrus communis) doesn’t ripen on the tree, at least not from the point of view of the consumer. If you leave it long enough for the outside to soften, it will be too ripe inside, with a mushy consistency. You can use overripe pears in cooking, but you wouldn’t want to eat them fresh.

Moreover, you can’t rely on the pear’s appearance to tell you when it’s ready to harvest. True enough, most varieties change color at least a bit as maturity approaches, but many are still green or only somewhat yellowish when ripe. And even if the fruit becomes flushed with red, that doesn’t necessarily mean that it’s ready to harvest.

Nor can you solely rely on a calendar date. Some pears ripen as early as August, but most in September or October, more rarely in November … but the date will vary according not only to your climate, but to the weather starting from the time the tree first bloomed the previous spring.

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Pear harvesting. Photo: Apple and Pear Australia, Flickr

To know if a pear is truly ready to be harvested, hold the branch in one hand and the fruit in the other, then lift it upwards from its hanging position as you twist very gently. If the pear remains firmly attached, it’s not ready to harvest. If it comes off easily, get out a few baskets: it’s time to get at it!

After the Harvest

But the European pear is not yet ready to eat, even when it’s ready to harvest. It will still be too hard and astringent. It simply doesn’t ripen on the tree! Instead, place it on a shelf, preferably in the dark, or in a paper bag, and store it at room temperature for a week or two until it does soften up. Then it will finally be ready to eat.

There is even a term for allowing a pear to soften until it’s edible: it’s called bletting.

Asian Pears: Different Rules Apply

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Asian pears do ripen on the tree. Photo: User:Fir0002, Wikimedia Commons

The above information applies only to the European pear (P. communis), with its oblong shape, wider at the base than the top. The Asian pear (P. pyrifolia), round as an apple, ripens on the tree just like most fruits do.20170923A

International Save-a-Plant Week



Actually, there is no International Save-a-Plant Week … but I think there should be one.

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Gorgeous late summer flower beds at the International Peace Garden, Ottawa. All these plants will soon be pulled out and destroyed. Photo:

This would be a week in late September or early October when gardeners would be allowed to help themselves to cuttings of annuals and dig up tender bulbs in public spaces. I’m thinking of all the splendid plantings of so-called annuals that are actually tender perennials—plants like coleus, dahlias, begonias, flowering maples, cannas, feather grasses, hibiscus, echeverias, ornamental bananas, elephant ears and so much more—that presently fill traffic islands, roadside carpet beds and city park flower beds.

These gardens are actually stunning right now, but all of these plants will soon be pulled up and destroyed by teams of municipal employees. In warmer climates, they pull “summer annuals” to make room for winter ones; in cold climates, they’re often replaced by tulip bulbs … or the beds are simply left empty until the following spring.

A Bit of Organization


This would have to be organized: we don’t want people rampaging through public gardens like Swedish soccer fans! Photo: Frankie Fouganthin, Wikimedia Commons

Of course, I’m not promoting allowing novice gardeners to rampage through public parks, taking cuttings and pulling plants indiscriminately. Many plantings are permanent ones and you need a bit of experience to tell the difference between perennials and shrubs that need to be left in peace and the temporary plantings that will soon head to the trash heap. You’d need to set up special days and schedules and have an employee or master gardener who knows their plants there to oversee and direct.

Or let local garden clubs harvest plant material, then offer it to gardeners.

Failing that, municipalities should at least put their pulled plants in piles in designated spots and let people rummage through them. And if you don’t think anyone would pick their way through piles of wilting refuse plants, you don’t know gardeners!

Criminal Mind

I must confess that each year at this season, while I see those luscious beds brimming with gorgeous plants that have no idea they’re about to meet their maker, I’m sorely tempted to sneak out after dark and do a bit of guerrilla plant harvesting myself. In fact, only the thought of arrest and possible imprisonment really holds me back.


I’d rather think of myself as a horticultural Robin Hood than a plant thief. Illus.:

I’m not even afraid of public embarrassment: you could put me on the front page of the local newspaper with a caption “Garden Writer Caught Stealing Coleus Cuttings” and I wouldn’t be ashamed at all. I know a lot of people who would see me as a sort of horticultural Robin Hood: stealing from Big Brother to give to the people.

So, what do you think? Don’t gardeners everywhere—and the plants that are about to die!—deserve an International Save-a-Plant Week? Bring it up at your local municipal council meeting. Maybe something can be done!20170922B

Overwintering Hardy Water Lilies

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Even hardy water lilies may need a bit of winter protection. Photo: Kelvinsong, Wikimedia Commons

Here’s a curious contradiction: hardy water lilies (Nymphaea spp.), even those growing naturally way up north in the snow-covered boreal forest, are incapable of tolerating freezing! That’s because, even in the Far North, the water of a lake rarely freezes very deeply. So even aquatic plants adapted to very cold climates have never had to adapt to freezing. Therefore if you’re growing hardy water lilies in a garden pond, you have to take that into consideration.

In regions where ice comes and goes in the winter (usually zones 8 and above, as well as in certain zone 7 areas), the water in a pond will never freeze to any great depth and you can put your hardy water lilies just about anywhere as long as the crown is covered with water at all times, but in any climate where solid ice does form, you have to assume that the water will freeze to a depth of 12 to 16 inches (30-40 cm). Since water lilies are usually grown in pots placed on the bottom of the pond, that elevates their crown to about 8 inches (20 cm) above the bottom. In other words, if you add the two together, you’re essentially looking at needing a pond depth of 2 feet (60 cm) or more to ensure that the crown is not in danger of freezing.

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You can move the water-lily’s pot to the bottom of a neighbor’s swimming pool for the winter.

If your pond is over 2 feet (60 cm) deep, just move your water lily pots to the deepest part for the winter. Or, if you or a neighbor has a swimming pool, place them at the bottom of the pool for the winter. Another possibility is to dig a trench in the garden and to bury the pots below the frost level.

The easiest solution, though, is to find cultivars capable of growing at a good depth (60 cm or more), such as ‘Sultan’, ‘Comanche’, ‘Attraction’ or ‘Moorei’, and to simply place them at that depth permanently. Yes, they’ll be slower off the mark in the spring (the deeper a water lily grows, the longer it takes for its leaves to reach the water’s surface), but at least you’ve saved yourself the effort of sloshing knee-deep through the cold water of a pond each spring and fall as you carry your water lily pots back and forth.20170921a Kelvinsong, WC

How Bulbs Plant Themselves


Contractile roots pull bulbs down to the proper depth.

For a long time, scientists wondered how bulbs, which grow from seeds that germinate at or near the surface of the soil, end up being buried so deeply. And they discovered that it’s because they produce unique roots called contractile roots. These begin the season like any other root, penetrating deep into the soil, but then they begin to contract, becoming condensed and wrinkled, like an accordion that deflates. Since the lower end of the root clings to the soil particles in its vicinity, the result is that they pull the bulb downward. Thus, the bulb actually plants itself!

The Right Depth


Traditional planting depths for spring-flowering bulbs.

Each species of bulb at its preferred soil depth, one that shelters it from predators and drought, and may take a few years to reach it, descending deeper and deeper each season as the bulb, tiny when it germinates, grows in size. The bulbs even adjust to the type of soil, descending deeper in light, airy soils than in dense, heavy ones.

Studies have shown that the main influence in bulb depth is actually sunlight. Contractile roots react to light penetrating the soil, specifically rays at the blue end of the spectrum, pulling the bulb deep enough into the soil that the penetration of blue rays no longer influences it. And the degree of tolerance to blue rays varies according to the species, explaining why some bulbs descend more deeply than others.

In Your Own Garden

If you pay attention, you can actually observe the phenomenon of contractile roots in your own garden. Here are two examples:

  • While planting bulbs in the fall, you accidentally drop one and it lies on the ground all winter. (And who hasn’t done that!) You’ll find the lost bulb in the spring, as it will bloom even if it’s only partly buried. But come summer, it will have disappeared entirely, pulled underground by its contractile roots. Within two or three years, it will have planted itself at the right depth for the type of bulb in question.
  • Or you planted lily bulbs at a depth of 6 inches (15 cm), as recommended on the planting instructions that came with them. Now, some lilies adapt very well to that depth and will remain there. However, when you decide to divide your lilies five years later, you will find that some have “migrated” to a depth of 8 inches (20 cm) and others to a full foot (30 cm), according to their true preferred depth.

Tulips Like It Deep

Most tulips actually like much deeper plantings than bulb companies usually recommend: some botanical tulips will descend to a depth of 2 feet (60 cm) over the years!


Bulbs often pull themselves down below depths where predators can reach them.

The theory for this extreme depth is that the bulb is trying to protect itself from bulb-loving marmots found in their natural environment. The squirrels of your own garden also like tulip bulbs, but they won’t dig anywhere near 2 feet (60 cm) to find them. They’ll even give up past 8 inches (20 cm)! That’s one of the reasons why tulip bulbs planted 1 foot (30 cm) deep often perennialize better than the tulip bulbs planted at the usually recommended 6 inches (15 cm). (Read more about this phenomenon at Deep Planting Prolongs Tulips.)

The bulbs that plant themselves: ain’t nature wonderful?20170920A

Plants: Not Good at Multitasking


20170919A.jpgWe all know people who seem capable of multitasking (performing multiple tasks simultaneously): answering the phone while filling in a crossword, weeding the vegetable garden while watching the kids, washing the baby while mowing the lawn, and so on.

But plants are not very good at multitasking. They prefer to do one thing at a time, performing their various tasks—rooting, growing, flowering, producing seed, preparing for winter, lying dormant, etc.—successively. Thus, when they’re in bloom, they’re not inclined to produce new roots, new stems or new leaves, nor when they’re producing seeds, and when they’re dormant … well, they won’t do much of anything!

This affects the way we garden, or at least should affect it. Unfortunately, too many gardeners expect their plants to do everything at the same time and come away disappointed or confused when that just doesn’t work.

Here are some examples of situations where it is better to let our plants do one thing at a time:

  • When you transplant or divide a plant, pinch off its flowers. It may pain you to do so, but you’ll reap the rewards later, as a pause in blooming encourages the plant to concentrate on producing a good root system. Once it is well established, you can let it bloom again … and now it will bloom much more heavily.
  • Avoid supplying nitrogen fertilizer (one where the first digit on the label, nitrogen, is the highest) to plants that are “hardening off” (preparing to enter dormancy), especially in late summer. Too much nitrogen at that time can stimulate off-season growth that will be weak and subject to cold damage and even reduce the plant’s overall hardiness.
  • Remove any fruits in the first year or two after planting small fruits (blueberries, currants, bush cherries, etc.) and for up to five years after planting fruit trees (apples, plums, pears, etc.). This will give the plant time to settle in well before having to invest its energy in bearing fruit.

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    Cutting back salad greens just before they mature will often encourage  them to start all over. Photo: Kent Tarrant

  • Harvest leafy vegetables like lettuce, arugula and spinach just before they reach their peak by cutting them back to about an inch (2 cm) above the ground. This will prevent them from producing a flower stalk and thus thwarts their goal of producing seed. It’s a well-known fact that when leaf vegetables “bolt” (the term used when they produce a flower stalk), they become bitter and inedible, but if you harvest them early, most will resprout from the base, producing new leaves … and giving you a second harvest.

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    Let broccoli resprout after you harvest it. Photo:

  • Similarly, rather than pulling out broccoli plants after harvest, simply leave what remains of the plant growing. Since you prevented it from blooming (what you harvest on broccoli are its immature flower buds), the plant will try to produce new flower stalks, giving you a second crop. This works too with cabbage and kale … if there’s still a few weeks left in the growing season, they’ll have time to produce a small head (cabbage) or a cluster of new leaves (kale).
  • If you buy a perennial that has been forced into early bloom for May sales (often the case with echinaceas and gaillardias, for example), it will pass the rest of the season trying to keep on blooming and will barely put on any growth at all, no matter how much you baby it. Thus it won’t produce the solid root system it needs to survive the winter. As a result, you often you’ve paid for a perennial that behaves like an annual and doesn’t come back the following spring. The secret to “re-perennializing” such a plant is to not to let it bloom at all the first year, but rather to remove not only the flowers that were present at purchase time, but every flower that it tries to produce that season. Since you thwart its effort to keep putting its energy into blooming, the plant will invest it instead in a robust root system, dense foliage and hardening off for winter. Then, the next summer, once it’s well-established, let it bloom its head off and you’ll find it’s gained in both vigor and hardiness.
  • Deadheading (removing the faded flowers) from certain shrubs and perennials (roses, golden marguerites [Anthemis tinctoria], perennial salvias, etc.) will prevent them from putting energy into producing seeds and will therefore often help the plant rebloom that same season.
  • Remove flowers and flower buds from cuttings and pinch even the tip of their stem to stop them temporarily from growing and blooming. That way the stem will focus on rooting.

Take full advantage of the natural tendency of plants to unitask and encourage them to do what you want them to do. After all, it is your garden!20170919A

The Rule of Three


Plant bulbs at at depth 3 times their height and space them at 3 times their diameter.

The basic rule for planting bulbs is to plant them at a depth equal to three times the height of the bulb and to space them at three times their diameter. In very cold climates (zone 3 or less), it may be helpful to bury hardy bulbs deeper than normal, up to a depth equal to five times the height of the bulb. That way the bulb will be better protected against the cold.


Tulips perenniallze best when planted 1 foot (30 cm) deep. Photo:

It is also worthwhile making am exception for hybrid tulips, like Triumphs, Parrots, and Darwin Hybrids. You’ll find that they will be more more perennial and better protected from squirrels if you plant 1 foot (30 cm) deep. That’s about twice the usual recommendation.

Even so, only plant tulip bulbs extra deep when you can offer them loose, well-drained soils. In heavy clay soil, which the tulip’s spring shoot  has more difficulty piercing, it is better to stick to the original rule of three!011.K