Introduction to Bougainvilleas

Bougainvilleas are vigorous tropical vines that bloom in a range of vibrant, jewel-toned hues that create cascades of eye-popping color. With woody vines growing up to 40' long, bougainvilleas put on a spectacular show when in full bloom.

About Bougainvilleas

As versatile as they are beautiful, bougainvilleas are often trained to grow on trellises, arches, and against walls. They're at home draping over stone walls and adorning planters — even hanging baskets! They can also be pruned to maintain a shrubby shape and planted in rows to create a hedge. Most varieties have sharp thorns though there are some thornless varieties.

Native to eastern South America, the plants are perennial in frost-free climates and generally bloom for at least four to six weeks in shades of magenta, red, orange, pink, yellow, and white. The papery "flowers" are, botanically speaking, modified leaves called bracts that surround tiny white flowers in the center. The vines are often evergreen, though the plant may drop its leaves during prolonged dry spells, resuming growth when watered. Overall, these reliable plants are drought-tolerant, resistant to pests and diseases, and easy to grow.

There are hundreds of varieties, most of which are hybrids created by crossing the numerous Bougainvillea species. In regions near the equator, they'll flower nearly year-round. Elsewhere, they typically bloom for four to six weeks, usually in spring and fall when the day length is about 12 hours.

Left on their own, the vigorous vines will ramble over the ground or cascade over walls. Although the plants can "climb" using their curved thorns, they are best trained to a trellis or other support by tying the vines with soft plant ties or strips of fabric.

Pronunciation: boo-gun-VILL-ee-uh

Growing Zones for Bougainvilleas

Bougainvilleas are perennial in USDA Hardiness Zones 9-11. In colder regions, they can be grown as annuals or overwintered indoors. Although established vines can withstand a light frost, the plants won't tolerate a hard freeze.

Choosing a Site to Grow Bougainvilleas

Bougainvilleas love heat and sun, making them an ideal choice for south-facing walls where they'll get at least 6 hours of sun per day. They require well-drained soil that is slightly acidic.

Keep in mind that most varieties have sharp thorns, making them unsuitable for areas with foot traffic. Plan ahead for the vigorous vines by erecting a support at planting time. Wooden and metal trellises and wire grids are good choices. Dwarf varieties produce vines from 3' to 6' long and are suitable for planters and hanging baskets.

Planting Instructions for Bougainvilleas 

Loosen soil to a depth of at least 12" and mix in some compost and/or slow-release fertilizer prior to planting. Handle young plants carefully to avoid damaging the fragile roots. Set the plant at the same depth as it was in its original container. Install your trellis or other support at planting time. Apply a thin layer of organic mulch, such as pine straw, keeping it a few inches from plant stems to avoid rot. Water plants as needed during their first growing season to keep the soil slightly moist but not saturated. The plants will grow slowly at first as they establish their root systems and may produce few flowers the first year; however, in season two and beyond you'll be rewarded with stunning blooms for years to come.

Fertilizer for Bougainvilleas

Bougainvilleas need regular fertilizing to support vigorous growth and bountiful blooms. Apply a thin layer of compost or a granular fertilizer to the soil beneath the plants each spring. Avoid over-fertilizing, especially with nitrogen, which will encourage lots of foliage at the expense of flowers. 

Bougainvillea Pests and Problems

Bougainvilleas are generally pest- and disease-free. Occasionally, aphids and mites will attack the foliage; these can be controlled with insecticidal soap. Avoid overwatering to discourage root rot.

Ongoing Care for Bougainvilleas

Once mature, bougainvilleas are relatively tolerant of drought. Once plants are established, water in-ground plants thoroughly every three weeks or so. Container-grown plants will need more frequent watering. 

Left unpruned, the vines can become rampant and overwhelm their supports, so keep their grown in check with regular pruning. The plants bloom on new wood, so you can prune the plants in late fall or very early spring to encourage a flush of new growth. You can also prune them back after they're finished flowering. You can do light maintenance pruning, such as removing dead wood or cutting back errant vines, at any time. Wear sturdy gloves; some people get a rash from contact with the foliage, and most varieties have sharp thorns.

In cold climates, you can bring potted plants indoors for the winter. Place them in a sunny window and reduce watering to avoid root rot and allow the plants to rest. 

Frequently Asked Questions about Bougainvilleas

Why do the flowers only last four to six weeks?

Nothing is wrong. Bougainvillea blooms in cycles, much as roses do. A flush of color lasts roughly five to six weeks, then the bracts fall, the plant puts on a round of new leaves and stems, and if it is growing well another flush follows on that new growth.

What you see as flowers are bracts, three papery modified leaves surrounding the tiny white tubular true flowers, which is why the common name is paper flower and why the display lasts as long as it does. A vine in good condition produces so many, so continuously, that most gardeners never notice the old ones going.

In California the strongest flowering tends to come in spring, fall, and winter, and the long days of midsummer often slow bract formation, although some varieties keep going through summer if they are well cared for. A plant that colors up, drops, greens up, and colors again is on schedule.

My bougainvillea has lots of flowers but very few leaves. What should I do?

Prune. Cut the stems back after the flowers fade and the plant will respond with new growth carrying full green leaves. Each new stem will have leaves along its length and flowers at the tip, typically within about six weeks. Use this if you want a better balance of foliage and bloom rather than solid color.

It bloomed heavily the first year and hardly at all since. Why?

Four causes account for nearly all of these, and they have different fixes.

Too much nitrogen. This is the most common. Bougainvillea fed like a general shrub, on a product high in the first NPK number, responds by making vigorous foliage instead of flower buds. It looks healthy and well fed, and you have inadvertently selected for leaves. Stop any feeding above the label rate or frequency, then switch to a product labeled for flowering plants or for bougainvillea specifically, where phosphorus and potassium are high relative to nitrogen. Apply it per the current label, typically every four to six weeks in the growing season, and stop in late fall and winter. Do not swing to a bloom booster chosen for phosphorus alone, because excess phosphorus interferes with nutrient uptake just as excess nitrogen does. After two or three growth cycles bloom should recover; a plant conditioned by years of high nitrogen may take a full season, and erratic feeding resets the clock.

Root restriction, in one of two opposite forms. A plant whose roots have nearly filled its pot often blooms prolifically, because a full root mass cannot make more roots and the energy goes to reproduction. That is legitimate and harmless. True root starvation looks different: growth slows or stops, new leaves come in smaller than the old ones, foliage pales, the plant does not perk up after watering, and water runs straight through and out the drainage holes. If it is blooming and growing steadily, leave it another season. If growth has stalled and the plant is staying in a container long term, move it up, and expect a cycle or two of lighter bloom while the roots fill the new space.

Day length. Flowering is sensitive to photoperiod. In most regions bloom is strongest in spring, fall, and early winter and lighter through the long days of summer. That is the plant's rhythm, not a fault in your care, and you cannot reliably manipulate it without greenhouse-level control.

Maturity. A young plant spends its first season on roots and branches. If the plant is vigorous, the leaves are full sized and dark, and it is simply setting fewer clusters than it did at first, it may just have settled into its real rhythm. What signals a genuine problem is a sharp collapse rather than a gentle decline.

Should I stop watering to force blooms?

No, and this is the most persistent piece of bougainvillea folklore. In their native habitat these vines often bloom as rain returns after a dry spell, and that has hardened into a rule that drought forces flowers. What is actually true is narrower: the soil should dry down a little between waterings, and letting the foliage wilt very slightly before you water can encourage bloom. Soggy soil is what suppresses it.

What is not true is that established plants need no water. In a hot dry inland summer a bougainvillea appreciates regular deep watering through the growing season, and depriving it costs you growth and flowers rather than buying them. The plants that appear to thrive unwatered along the coast or in Hawaii are living on ambient humidity that inland gardens do not have.

Practically: water deeply and less often rather than briefly and daily, let the top inch dry before the next watering, and never leave the soil wet. A plant that wilts hard and repeatedly is losing ground, not being encouraged.

My bougainvillea is stressed with small leaves and dried flower clusters after heavy rain. How do I recover it?

Overwatering. Cut the frequency back sharply. While it is recovering, water deeply no more than once a week, then check the soil three or four days later; if it is still moist several inches down, wait. Water only when it is dry at that depth. This recovery schedule is more frequent than an established in-ground plant needs, so return to the longer intervals above once new growth looks normal. Small leaves are a stress signal and should improve as the schedule corrects.

My newly planted bougainvillea is wilting and dropping everything. Will it live?

Probably, and there is very little you can do to hurry it. Water faithfully once a week, soaking the whole root mass rather than wetting the surface. A healthy plant recovers from transplant shock; in a bad case the top dies back to the ground and new shoots still come from the crown. It may look terrible for weeks and sulk for a couple of months before it decides to grow. Keep the water steady and prune off what has clearly died.

The same applies when a root ball breaks apart during repotting. There is nothing useful to do but water regularly, let the top inch dry between waterings, and wait. Starting over is almost never necessary.

What is the right way to get one in the ground?

This is where it most often goes wrong. Bougainvillea has a coarse, brittle root system with little fine root to hold a root ball together, and it strongly resents disturbance. Do not tease the roots apart, do not knock the soil off, and never pull the plant out of its container by the stem.

Two methods work:

  • Cut the container off. Slit the pot down the sides with a knife or tin snips and peel it away, leaving the root ball intact, then set it in the hole without squeezing it.
  • Slide the container up and off. Dig and size the hole first. Cut the bottom out of the pot, set pot and plant together into the hole, then backfill around it while easing the pot upward and off over the branches, ideally with a second person shoveling. As long as soil stays packed against the roots the whole time, the plant barely registers the move. You will scuff or snap a few vining stems getting the pot past them; prune those off afterward, and count it a good trade.

Set the top of the root ball level with the surrounding soil, backfill with the soil that came out of the hole rather than a heavily amended mix, water it in to settle everything, and then leave it alone.

How far apart should I space them?

Spacing depends on the variety and on how long you are willing to wait. Most of the growth goes up rather than sideways, so closer spacing buys faster coverage at little long term cost.

Against a wall, expect 15 to 30 feet of height with most varieties maturing around 6 to 8 feet wide. On a long wall, planting on about 6 foot centers gives good coverage in reasonable time. Fill the gaps meanwhile with a temporary shrub or a mass of flowering perennials and pull those out as the vines want the room.

Along a fence, where the vigorous types run much larger, a frost free climate can produce 25 to 50 feet of growth with a 25 to 35 foot spread. For quick coverage set plants 8 to 10 feet apart; if you can wait, 15 to 20 feet apart is enough and you will spend less time cutting them out of each other later.

Those ranges are not a contradiction. Compact and dwarf selections sold for containers stay near the small end while old vigorous cultivars in a frost free coastal or desert garden reach the large end and keep going, so ask what variety you are buying and what it does locally. Avoid very tight spacing: planting at a foot apart wastes plants and money, covers no faster than the roots and the season allow, and leaves a congested tangle that is hard to prune.

If you are mixing in star jasmine along the same fence, it twines and can add up to 20 feet of vine in a season. Set plants 3 to 4 feet apart for quick coverage, or 6 feet apart if you can wait four or five years, and pinch the growing tips to make it throw more vining stems and fill in denser.

Will it damage my house, and how should I support it?

It cannot attach itself to your house. Bougainvillea has no clinging pads or aerial roots of the kind ivy uses to grip a wall. What it has is long, arching, thorny canes that scramble through anything nearby, and with nothing to climb it simply piles up on itself into a mound. So it is not a masonry or shingle problem the way a self clinging vine is, but a mature plant is heavy and it will get into a soffit, a gutter, or under a roof edge if you let it grow there.

For a house wall, use a sturdy trellis set about three feet out from the wall. That gap keeps air moving behind the plant, leaves you room to prune, and means the house can still be painted or repaired without dismantling the vine. Wire and lattice both work as supports. What matters is the attachment:

  • Tie loosely with a soft material that will not cut into the bark, leaving room for stems to thicken. A tie that fits perfectly today is a girdle in two years.
  • Use a loose loop rather than a tight wrap so the cane can move a little.
  • Ties break down in the sun. Fold their replacement into your pruning: whenever you go up to cut the plant back, check and renew every tie you can reach.
  • Fasten the wires or the trellis to something structural. A mature bougainvillea carries real weight, especially wet.

Should I keep the stake that came with my plant?

While the main stems are still flexible and green, a stake will hold a young plant upright. As the stems mature and turn woody the plant develops its natural sprawling or cascading form anyway, and once woody they carry their own weight. Remove the stake early and the branches tend to spread low and creep along the ground, so keep it if you want an upright form. Check the ties frequently, because thickening stems girdle against them, and replace ties and stake as the plant grows.

Can I train three plants into a tree?

Not literally, since these are vines, but you can build a good braided standard. Pick a large pot and fill it with a mix as close as you can get to what the plants are already in. Push a tall, sturdy stake into the center. Move all three plants in together, spaced as close around the stake as you can and with as little root disturbance as possible, then braid or wind the stems around the stake, trimming off side branches that get in the way. If the stems are young and pliable you may be able to braid them around each other without winding on the stake, but you still want a stake underneath to carry the weight.

Tie loosely with soft ties so nothing bruises or girdles, and check those ties every few months. Once the braid reaches the height you want, perhaps three feet, let the growth above it go where it likes; much of it will fall into a weeping shape you can then shape by pruning.

One honest expectation: standards, and braided ones in particular, are normally trained from young plants as they grow. Older nursery plants with set stems may never quite look like the ones in the display garden.

How much sun does it actually need?

Six hours a day of direct sun at minimum to flower properly. Below about four hours it may start dropping leaves, and growth visibly slows. There is a useful test for what counts as direct sun: the plant should cast its own sharply defined shadow. Bright but diffused light does not qualify.

Alongside light it wants warmth, moving air, and relatively low humidity, with the soil drying slightly between waterings. Indoors or in a sun room, supplement with a grow light if the natural light falls short, and give each plant elbow room. What matters is sun on the vine, not on the pot.

How big a container does it need, and what should I fill it with?

Start much larger than the plant looks like it needs, because this is a plant you do not want to repot. A container plant that will not climb or flourish has very often been potted on once too often, or was put in a pot it outgrew within a season and has sulked ever since.

  • Ten to fifteen gallons is the working range for a plant meant to climb, and a pot that size will serve for years.
  • For real size on a trellis or patio cover, treat 15 gallons as the minimum, or use a half whiskey barrel. Established plants put on a good six feet in every direction in a season and fill a large pot readily.
  • Do not choose a small pot to force flowering. These plants do bloom best slightly rootbound, but that is what happens naturally in a large pot after several years. A pot that is too small runs the plant out of water and nutrients and stops it climbing altogether.
  • Moving from a five gallon nursery pot, go straight to a 15 gallon container or a barrel rather than stepping up in stages. Each step is another root disturbance.

For the mix, use equal parts garden soil and potting soil. That ratio does two jobs neither ingredient does alone: straight garden soil in a pot is hard to keep evenly moist and it compacts, while straight potting soil drains well but is very light, and a bougainvillea trained up a trellis becomes top heavy. A light pot with a heavy plant blows over in the first real wind. In a windy spot that is not a small consideration, and it is worth buying the heaviest pot your budget allows. Plastic, fiberglass, ceramic, and stone are all horticulturally fine.

How often do I water and feed a plant in a pot?

Water thoroughly, then let the mix become moderately dry before watering again, putting on enough that water runs from the drainage holes so the whole root ball is wetted. Expect to do this nearly every day in summer despite the plant's reputation for drought tolerance: the root system is small relative to the top growth and a container cannot store much. Water generously through the whole first season while the plant builds the root system it will live on; after that, deep watering once or twice a week suits an in-ground plant or a very large container.

These are heavy feeders, and consistent feeding is what separates a plant that blooms for a few weeks from one that blooms nearly year round. With good light and a steady routine a container plant will carry bracts for ten or eleven months.

  • Feed every week or two through the growing season rather than heavily and occasionally.
  • Use a water soluble fertilizer at reduced strength, diluted well below the full rate, so frequent feeding does not accumulate salts. A balanced analysis such as 20-20-20, or one with a higher potassium share, suits the plant. Hibiscus food is also a reliable and easily found choice.
  • Follow the dilution and frequency on the current label of the product in your hand. Concentrations and directions vary between brands and have changed over the years.
  • Flush the pot with plain water every few weeks on this schedule, especially in a hot dry climate where evaporation concentrates whatever is left behind.

A slow release granular product is generally the easier choice for in-ground plants, applied roughly every five or six weeks following each bloom cycle. Whatever you use, heavy nitrogen gives you leaves at the expense of bracts.

One potted plant is thriving and its twin is collapsing. Why?

Almost certainly water that is not reaching the roots. Containers in full sun dry out fast, and once the mix has shrunk from the sides of the pot, water runs down the gap and straight out the drainage holes while the root ball stays dry. You water daily and the plant still starves.

The fix is immersion: stand the whole pot in a bigger tub of water for about fifteen minutes, which saturates the mix through and drives out the air pockets. Then deal with root temperature. A black nursery pot in full sun can heat the root zone past what the plant can stand, so cluster rocks or decorative pots around it to shade the sides, or drop the nursery pot inside a larger one.

Do not repot to fix this. If the plan is to plant it in the ground in a few months, leave it in its nursery container until then.

My pot sits on a concrete patio in full sun. Will the roots be all right?

This is the one genuine hazard of container growing in a hot climate: a container in full sun absorbs enough heat to cook the roots, and concrete makes it worse by re-radiating heat into the pot from underneath and from the side all afternoon.

The fix is insulation. Set the planted container inside a larger decorative one and pack insulating material into the gap. The outer pot takes the sun and the inner one stays much cooler, and it looks better than a nursery container besides. Placement helps too: a low wall that shades the container while leaving the trellis above it in full sun is close to ideal, since the plant wants sun on its top growth and cool roots.

My leaves are pale green with dark green veins and the flowers look faded. Why?

Pale foliage with dark veins typically indicates iron deficiency, a nutritional problem separate from normal fertilizer needs, and the plant may need an iron supplement applied at soil level. Check your watering at the same time: water should penetrate at least 12 inches into the root zone, because roots in deeper soil that stay dry cannot take up the iron that is there. Correcting both together should restore the color.

Why are my old leaves turning red and crispy?

Mature leaves on an otherwise healthy plant develop bright red or reddish edges, turn brittle, and look worn before they drop. That is natural aging; bougainvillea sheds older foliage to make room for new growth, and cold winter weather accelerates the reddening. It fades with time or goes with the leaf. As long as new growth is green and the rest of the plant looks well, there is nothing to do.

In genuine desert heat, leaves can brown and curl at the margins while the soil is still moist. That is heat and dry wind pulling water from the foliage faster than the roots can supply it, not a watering fault, and afternoon shade is the answer.

Why did my plant drop all its bracts after I brought it home?

Moving, shipping, wind, a sudden overwatering, or any comparable shock can make a plant drop many or all of its bracts at once even though they were healthy on arrival. This stress drop is separate from normal bract fading. Settle the plant in bright light, water consistently but not heavily, and do not try to fertilize it out of the problem. It will start setting new bracts as conditions stabilize.

What is the white fuzz on my bougainvillea, and why is it sticky?

The stickiness is the clue, and it points away from the first guess most people make. Powdery mildew is a dry, dusty white coating and leaves nothing sticky. White fluff plus a sticky film means a sap feeding insect, most often mealybugs, which look like small tufts of white cotton tucked into leaf axils and stem joints. The stickiness is honeydew, their excreted sugar, and black sooty mold usually follows on top of it. Scale, which looks like small flat discs, produces the same honeydew.

Sort out which you have before treating. For mealybugs and scale, start mechanically: prune out badly infested growth, wipe or pick off what you can reach, isolate the plant from the rest of the collection, and wash off the honeydew, since the sooty mold goes when its food supply does. If you go further, use a product whose current label lists both bougainvillea and the pest, and follow it exactly on rate, timing, protective equipment, and reentry.

If it really is powdery mildew, dry and dusty rather than sticky, the answer is cultural. It appears where air circulation and light are poor and foliage stays damp. Prune the affected parts, then fix the conditions: more light, more space between plants, and a small fan on low, which does a surprising amount of work in a crowded sun room. A problem spreading plant to plant in an enclosed room is telling you they are too close together, too wet, and in air that is too humid and too still.

Something is eating the new growth and leaving black specks

Those specks are frass, which is insect droppings, and they are the classic sign of caterpillars feeding above. The usual culprit is the bougainvillea looper, almost exactly the color of the leaves and stems, feeding mostly at night and very hard to spot in daylight. Go out after dark with a flashlight and look along the leaf edges and at any rolled or curled new growth; you will usually find them.

Handpicking works on a small plant, and pruning out the chewed growth removes a good share of the population along with the damaged leaves while encouraging the fresh growth that carries the next flush of bloom.

If you treat, Bacillus thuringiensis subspecies kurstaki is the usual choice, sold under several brand names. One correction worth making, because it is repeated constantly: Bt is a bacterium, not a botanical, and it is not harmless to insects generally. It kills the larvae of butterflies and moths, which is exactly why it works here and exactly why it needs care. Do not let it drift onto milkweed or other butterfly host plants, do not spray on a windy day, and do not spray open flowers. It is not toxic to people, pets, or bees. Use a product whose current label names bougainvillea, and follow its directions. A broad spectrum insecticide would kill beneficial insects here and is unnecessary.

White speckling on the leaves is a separate question with several possible answers: spray damage, watering problems, or the early stage of a fungal or bacterial disease. Pruning away the marked growth is a reasonable first response while you watch what happens next. If you use neem oil or any other horticultural oil, check the current label for bougainvillea, treat a few leaves first and wait a couple of days, and never apply oil in direct sun or high heat, which is how oils burn foliage.

Why are the colored bracts turning white or fading at the edges?

Pale discoloration spreading in from the bract edges on a plant that looked fine at purchase is most often thrips rasping the bract surface and leaving silvery stippling and streaks. It can also be botrytis in cool damp conditions, or simple water spotting from overhead watering onto open bracts in strong sun. Check for thrips by tapping a discolored bract over a sheet of white paper and looking for tiny moving specks.

If you find thrips, remove the affected bracts and rinse the remaining foliage. If conditions are cool and damp, move the plant somewhere warmer and breezier and water at soil level only. Water spotting fades as new bracts emerge once you stop watering overhead. Nutrient and watering problems do stop a plant blooming and dull it overall, but they rarely show up first as edge discoloration on the bracts alone.

What pests should I expect indoors?

Whiteflies, spider mites, and scale. Whiteflies are tiny flying insects on the leaf undersides; spider mites leave fine webbing on stems and a stippled look to the leaves; scale looks like small flat brown discs stuck to stems and branches and is easy to overlook until it is heavy. Caught early, insecticidal soap applied per the product label will control all three over several applications, and any product you use must carry a current label naming bougainvillea and the pest you have identified.

For a heavy infestation, immerse the foliage in plain water in a large container or dishpan and swish it gently for a minute to dislodge the pests mechanically, repeating every few days, then follow up with soap if they return. Good air circulation from a small fan makes an indoor pest problem much less likely to take hold in the first place.

How do I protect an outdoor plant from frost?

Bougainvillea is tropical and frost damages it. On a frost-exposed pergola in zone 7 or colder, expect dieback whenever temperatures drop into the 25 to 30 degree range, and no cultivar is meaningfully hardier than another. Cover or otherwise protect plants when temperatures fall into the low thirties, and keep them out of high wind, which shreds and dries the foliage.

To improve the odds outdoors: choose the warmest, most sheltered spot you have; grow the plant in a container you can move indoors before the coldest nights rather than planting it in the ground; give it overhead protection from an open lattice structure or pergola that breaks the worst wind and cold while still letting light through; and accept some dieback in a typical cold winter. Prune the dead stems back to live wood in early spring as new growth begins, and the plant will regenerate from the crown.

If stems have died back to bare wood but the roots are alive, expect new shoots from the base and main limbs in about six weeks. If the roots themselves froze, recovery is unlikely. For a marginal climate, 'Barbara Karst' is among the most cold tolerant selections available, though no bougainvillea is reliably hardy north of zone 9b.

How do I overwinter it indoors?

Bring it in when night temperatures start hovering around 50 degrees, before the first properly cold night rather than after it, and begin the transition in late September as nights cool. Set the pot outdoors by day and indoors each evening, extending the indoor time over about a week until it stays in around the clock. Some leaf drop during this shift is normal and temporary. Reverse the process in spring, starting around mid-April adjusted for your last frost date, with a few hours out at first and a week of lengthening days until it can stay out overnight.

Once potted, keep the plant in a container year round rather than replanting it in the ground, so you can move it easily each season without disturbing the roots.

From there you have two approaches, and the right one depends on how much light and space you have.

Keep it growing. This works with a sunny south or west window, a glassed porch, or a grow light delivering at least 12 hours a day. Hold the temperature above 40 degrees, ideally nights near 50 and days near 65; warmer nights give weak, leggy growth and worse pest problems. Keep the soil moist but never waterlogged, watering thoroughly once the top few inches dry and checking that the water soaks in rather than running down between the root ball and the pot wall. Aim for 30 to 45 percent humidity, raising it by misting or by setting pans of water among the plants, but in a cold climate keep it just over 30 percent so condensation on the windows does not cause mold. Feed regularly with a water soluble fertilizer per the label, and prune once or twice over the winter to keep the plant compact and give yourself cuttings. Expect modest bloom at best.

Or put it to sleep. With no bright space, move it to a cool, dark or very dim place such as an unheated basement, garage, or cool closet, above freezing and ideally 40 to 45 degrees. It will read the cold and darkness, stop growing, and yellow and drop its leaves. Water only enough to keep the soil from drying completely, do not fertilize, and do not prune; the stems are the plant's reserves. Trim only what you must to fit the space, and prune properly in early spring. If instead the plant drops everything and goes dormant where you had hoped it would keep growing, treat it the same way: cut watering right back, cut the plant back by about a third, watch for the first new leaf buds, and resume normal watering when they appear.

To wake it, move it somewhere bright and warm once outdoor temperatures are reliably rising, resume watering and feeding, and give it roughly four weeks of growth indoors in good light so the new shoots harden before they go outside for the season.

Be honest about what indoor overwintering delivers: a plant that survives to next season but drops most of its leaves and blooms very little meanwhile. The goal is keeping it alive, not keeping it pretty.

Why is my indoor plant weak and spindly?

Weak, leggy growth indoors almost always means the air is too warm or the light too dim. Above 65 degrees at night, or under less than about 12 hours of good light, the plant stretches and weakens. Move it somewhere cooler or add a grow light positioned a few inches above the canopy. If it is wilting despite moist soil, check that the pot is actually draining and that water is not just running down the inside wall, since roots in waterlogged soil cannot take up water and the plant looks thirsty while the soil is wet.

Do I need to deadhead, and how hard can I prune?

Ordinary types drop their spent bracts on their own and need no deadheading. The double flowered varieties are the exception: they hold everything and have to be cut off by hand if you want a tidy plant.

You can cut off spent flowers anyway, and there is a bonus in it, because cutting encourages new growth and the new growth flowers in about six weeks. On a plant you are training that is a useful lever: prune where you want branching and you get the shape and the bloom together. Prune lightly after each bloom cycle once the old bracts have dropped, cutting just above a leaf joint and leaving no stubs. On a container plant this also reduces how often you need to repot.

Hard pruning is well tolerated and is the standard way to hold a plant to its space; it does not cost you the season. The one caution is for a plant that has stalled and is recovering from establishment failure, where you should remove only dead or badly damaged growth until normal growth resumes.

My plant will not grow at all, in any season. What is wrong?

This is different from year-two bloom decline, and it is usually the site or the soil rather than your care. Bougainvillea does poorly in heavy clay without substantial amendment; roots trapped in an airless, wet zone will not grow no matter how correctly you water. Dig down beside the plant to the depth of the root ball and feel the soil. If it is dense and clay-like, work compost into the native soil 12 to 18 inches deep around the plant rather than piling it on top. Check the light as well, since below four hours of direct sun growth slows visibly and foliage thins.

In a container, establishment failure usually means the pot is too small or the mix stays too wet. Use a container-rated mix rather than garden soil for a young plant, and make sure the pot drains.

Recovery is slow either way. A plant that has stalled for months cannot be rushed back with fertilizer or hard pruning. Give it good light, well drained soil, and regular water without waterlogging, and expect it to take a full growing season to resume vigorous growth. Move a badly sited plant if you must, but know that it resents the disturbance and will take weeks or months to settle.

Will the roots break a drain pipe?

Probably not, though it cannot be ruled out. The roots grow down and outward and usually stay within the top foot of soil, and a root meeting a solid pipe normally deflects and grows elsewhere. What can happen over years is that roots grow around a pipe and gradually constrict it.

Modern sealed PVC is much less vulnerable than old clay or jointed pipe, because roots get into drains through leaks and open joints rather than by drilling through sound material. If your line is intact PVC and draining normally, the risk is low. The only way to know for certain is to dig and inspect, which will likely damage the plant more than the roots are damaging the pipe. Watching for slow drainage and having the line scoped if it changes is the more sensible approach.

Which varieties are worth looking for?

Remember first that you are choosing bracts, not flowers, which is why the display holds for weeks. Among the selections worth seeking out:

  • 'Barbara Karst', bright red shading toward a bluish crimson, flowers in sun or shade, begins blooming very young, and enjoys heat. A good first choice for a hot patio and the most cold tolerant of the common cultivars.
  • 'Royal Purple', the most striking purple on the market.
  • 'Dr. Barry', white and lavender, with a variegated form called 'Vickie' carrying gold and green leaves.
  • 'Juanita Hatten', dark pink, and a newer mutation of it whose green leaves are spatter painted with gold.
  • 'Sundown', apricot and vigorous, a good bloomer that feeds heavily even by the standards of this plant.
  • 'Hawaiian Torch', fuchsia, its bloom held compactly along an upright spike.
  • 'Texas Dawn', smaller pink flowers in very large clusters on a vigorous plant that needs cutting back.
  • 'Surprise', large two-tone blooms in clear pink and white, and an easy plant to get flowers from.
  • 'Double Pink', clear pink and vigorous, needing regular trimming, and one of the double flowered types that will not drop its spent bracts.

Can I use a low growing bougainvillea on a hillside?

For cascading color, yes. For erosion control, no, and it is worth being plain about that. What holds soil on a slope is a dense fibrous root system through the surface layers plus a continuous canopy that breaks the force of rain. Bougainvillea supplies neither: it is woody, its roots are coarse and brittle, and its cover is open at the base. It also takes a season or more to establish, and the slope is actively losing soil in the meantime. If holding soil is the real goal, handle the interim with mulch, an erosion control blanket, or jute netting, set plants across the slope rather than up and down it, and ask locally what is actually used for slopes in your climate.

Note also that "dwarf" covers two different habits. The truly sprawling or trailing selections mound and cascade and stay naturally low; the compact shrubby types stay small but grow upward and outward and need training to spread across a bank. Both are marketed as low growing. Read the grower's own habit description on the tag and pay as much attention to mature spread as to height, because on a slope the spread is what closes the gaps.

Finally, "little or no trimming" is not achievable with this plant. It is vigorous, it needs cutting back regularly to stay in bounds, and it flowers on new growth, so even the low selections need maintenance pruning. If you want a plant-it-and-forget-it slope cover, choose something else.

How do I propagate it?

Stem cuttings or layering. Be warned that plenty of experienced gardeners have failed repeatedly at cuttings even with bottom heat and good light, so take more than you need and do not take a poor strike rate personally.

Semi-ripe cuttings are taken in mid to late summer from the current season's growth once it has begun to stiffen and form bark. Take a piece six to eight inches long, strip all but a few leaves, dip the cut end in rooting hormone, and set it into moistened medium. An even blend of coarse sand and bagged potting mix works well; coir and perlite works at least as well and is easier to keep evenly damp. Keep the pots warm and humid, around 65 to 70 degrees, out of direct sun. A greenhouse, cloche, cold frame, or a pot inside a loosely perforated plastic bag on a bright windowsill will all hold the humidity that keeps a cutting alive long enough to root. New leaves along the stem mean roots have formed.

Hardwood cuttings are the same operation in midwinter using fully matured growth from the past season. Gardeners in warm climates often take these at the very end of winter, about six inches long from the newest wood, and hold them near 75 to 80 degrees under a vented cover.

Layering is easier and needs no equipment. In spring, while the plant is growing hard, bend a stem that is putting on new growth down to the ground, nick the underside lightly, bury the nicked section, and pin it with a bent wire or a stone. Check in late summer, and once there are roots, sever the stem from the parent and move the rooted section with as little root disturbance as you can manage.

That last point governs everything with this plant, and it is the main reason rooted cuttings and divisions are lost after they have already succeeded.

What should I know about the thorns before I plant one?

Treat them as a genuine hazard rather than an inconvenience. Mature bougainvillea carries long, hard, sharp spines set at the leaf bases that cause deep puncture wounds. Those punctures readily become infected or drive plant material under the skin, and retained thorn fragments are a documented cause of chronic inflammation, of infection in a tendon sheath, and of septic arthritis when the puncture is near a joint; some require surgical removal. Any puncture from these thorns that stays red, swollen, or painful deserves prompt medical attention rather than watching and waiting, and so does a wound with a fragment still in it. The sap also irritates skin, and some people get a rash simply from contact with the foliage.

Every bougainvillea is thorny, including those sold as thornless, which are merely less so.

  • Wear thick leather gloves, long sleeves, and eye protection whenever you prune, tie, repot, or move canes. Eye injuries are the serious risk, especially working overhead or reaching inside the canopy.
  • Wash any puncture immediately with soap and water and watch it.
  • Site the plant away from doorways, paths, play areas, and anywhere a person or pet moves quickly past, and keep canes off the route you walk to reach the hose.
  • Bag prunings rather than piling them, and keep them away from children and pets. The thorns stay sharp long after the wood dries.
  • On a tall wall most maintenance happens on a ladder. Have someone foot it, never reach out sideways, and hand any work near a roof edge or a power line to a professional. On a slope, secure your footing or work with a second person.

Is bougainvillea the right plant for a fence, and what else could I use?

Worth thinking about honestly before you plant sixty feet of it. In its favor: in a climate that suits it, nothing else gives that much color for that little water, and the thorny growth makes a fence genuinely hard to climb, which some gardeners plant it for deliberately. Against it: it is thorny everywhere, extremely vigorous, and it will overwhelm a chain link fence rather than politely covering it, and once established it is hard to remove and hard to keep in bounds. If you are the person maintaining that fence line, or you have young children using the yard, weigh that carefully.

Some alternatives that come up:

  • Star jasmine is far more manageable and pleasantly scented. See the spacing note above.
  • Carolina jessamine is easier to keep in check than star jasmine and flowers bright yellow in late winter. Note that every part of it is poisonous, including the nectar, so keep it away from where children play and away from grazing animals.
  • Evergreen honeysuckle and lavender trumpet vine (Clytostoma callistegioides) are both evergreen options for a hot fence in a mild climate.
  • Luffa, the sponge gourd, is an annual for zone 8 and warmer. It runs to about 30 feet in a season, flowers yellow, and dies with frost, which leaves a clean fence each winter. Young fruits are eaten as a vegetable and mature ones dry into scrubbing sponges. Harvest fruit small, and taste a small piece first: if any gourd or squash tastes bitter, spit it out and discard the whole fruit, because the bitter compounds cause severe stomach illness.

And if a hard winter appears to have killed a planting, wait before replacing it. Winter-killed leaves drop and new growth often begins about six weeks later, and even when the stem tips have died back the roots frequently push new growth in spring.