Taxonomy and origin
Bougainvillea is a woody climber from tropical South America, a scrambler armed with curved thorns 1 to 2 inches long that has to be tied to a fence, wall, or pergola or it sprawls where it lands. It belongs to the four-o'clock family, Nyctaginaceae. The genus is small: 18 species by one count, 14 by another. Bougainvillea glabra comes from Brazil and Peru. The plant carries the name of Louis Antoine de Bougainville, a French explorer who lived from 1729 to 1811 and is credited with finding it in South America, and the genus name marks the voyage he sailed around the world from 1767 to 1769.
None of that color is petal. Each cluster of three true flowers is wrapped in three to six papery bracts, and the bracts carry the pink, purple, red, orange, white, or yellow that people buy the plant for. The flowers themselves are tubular, about an inch across, and creamy white to yellow, tucked in far enough that most people never notice them. Because bracts are modified leaves, they hold their color for weeks while the flowers inside come and go. Up close, the two species behind most cultivars separate cleanly: Bougainvillea glabra has five-angled floral tubes and short bracts, while Bougainvillea spectabilis has rounded tubes, longer bracts, and stems covered in short hairs. The warm colors came later, from Bougainvillea peruviana, a Colombian and Peruvian species with rose to magenta bracts whose cross with B. glabra produced the lemon yellow, orange, and crimson forms grouped as B. x buttiana.
Bloom time
Outdoors in frost-free ground, bougainvillea blooms from spring through fall, and in the warmest places it flowers year-round. The color comes in cycles: an individual plant blooms on and off through the year, heaviest from spring into early summer and again from late summer into fall. Every one of those flushes forms on new growth, so a plant that has stopped putting out shoots has also stopped setting bracts. Once a flush opens it holds, and on a potted plant kept in a sunny spot the display lasts up to eight weeks. Age counts as well, since an established plant blooms over a longer stretch than a young one. The timing behind all of this is day length and temperature together: bougainvillea normally flowers during the short days of winter, and how much it flowers then depends heavily on how warm those weeks are. Where winter brings frost, the plant is dormant or indoors through that natural window, so the outdoor year runs spring to fall on whatever new growth it makes.
Leaves but no flowers: why bougainvillea stops blooming
The usual reason a bougainvillea covers itself in leaves and shows no color is water. Too much of it, or roots sitting in wet soil, makes the plant drop its bracts or stop blooming altogether. The opposite works as a trigger: mild drought stress brings on flowering even under long days, and commercial growers dry their plants to the edge of wilting on purpose to set a crop. At home the method is the same. Let the leaves wilt slightly before watering, staying short of the point where they will not recover, and flower buds generally appear four to six weeks after you start. As soon as buds show, normal watering resumes, and from that moment a blooming plant must never be allowed to wilt or it drops its bracts and flowers.
Sun is the second thing to check, and shade is no small handicap: in a partly shaded spot bougainvillea produces healthy, dark green leaves and few or no flowers. Feeding is the third, and it fails in a specific way. A high-nitrogen fertilizer is a common reason for a big green plant with nothing on it, because nitrogen buys foliage. Nitrogen and phosphate both matter to flowering, but overfeeding adds growth while holding bloom back, so the correction is less fertilizer at a weaker rate. Pot size belongs in the same group. Restricting the roots keeps bougainvillea from growing rampantly and appears to push it toward flowering, while a container that is too large delays bloom, which is why a plant just moved up a size or two often spends the season making stems.
Two more causes are about time. A bougainvillea planted in the ground grows rampantly and is reluctant to bloom for a couple of years after planting, which is normal behavior for a young plant. That early shyness is not a nutrition problem either: fertilizer and irrigation will likely delay flowers further, because these plants bloom better when they are neglected. The other cause is old wood. Flowering happens on new growth, which makes pinching and pruning part of getting any bloom at all, and a plant left uncut for years runs short of the shoots that can carry bracts.
What to check when it will not bloom
Order matters here, because two of the common fixes work against each other. Feeding and watering a plant that needs drying out will set the flowers back further.
Pots and winter care
North of the hardiness range, bougainvillea lives in a pot and comes indoors before the first freeze, the same arrangement that suits bird of paradise and other frost-tender tropicals. The container has to drain hard, because the root system is extremely fine and does poorly in peat-heavy, water-retentive mixes that hold moisture around those roots. Once the plant is inside, there are two honest ways to run the winter. You can keep it in active growth, which means the brightest window in the house, steady warmth, and light watering. You can also rest it, which means a cool bright room, very little water, no feeding, and no expectation of a leafy plant in midwinter.
The temperatures differ by which winter you pick. A resting plant is held at a night minimum near 50 F and can be kept above freezing with the compost fairly dry, though it will drop its leaves, while a plant kept actively growing is asked for consistent temperatures above 60 F with plenty of sun. For that cool rest, a bright spot that stays between 40 and 50 F works well: a sunroom, a south-facing window, or a well-lit basement. Growing temperatures run at normal room level, and the resting period stays cool but never below 50 F.
When flowering ends in fall, water less often, let the plant dry further between waterings, and stop feeding. A young potted plant, roughly one to four years old, takes a deep watering every three to four weeks through winter, adjusted for how warm the room is. Leaf drop through any of this is expected, since bougainvillea is semi-deciduous in cooler climates and shedding is part of its cycle. A bare plant in January is not a dead one, and bark scratched with a thumbnail shows green underneath. In February and March, rising light and temperature restart growth, and that is the signal to increase water again. Repotting, when the plant needs it, belongs in early spring, in a loam-based, peat-free compost.
Winter by zone
What winter asks of you changes every half zone, from ground plants that never come inside to pots that spend five months in a window.
Pruning and training
There are two good times to cut bougainvillea back, and both work: right after a bloom period finishes, or in late winter to early spring just before growth begins. Which one you use depends on the winter you get. Cutting after a flush keeps the plant in cycle, since the long growth that carried the last set of bracts can be cut back by half once the bracts fall, and that brings a second flush in late summer. A single late-winter cut fits colder ground better, because foliage left on the plant protects it from cold damage and a fall pruning takes that protection away. In a borderline zone the wait runs to the end of February or into mid-March before any cutting starts. Neither timing changes the rule underneath: the cut is what forces the new shoots that carry the next bracts, since the plant flowers on the current season's growth.
Bougainvillea takes a hard cut, and hard pruning is the tool for size: cut hard to restrict growth, and cut individual stems where you want the plant to branch. Branching is the whole point, because every new shoot tip is a place bracts can form. Pinching does the same job at a smaller scale, and the more you pinch after a flowering cycle finishes, the more the plant branches and blooms. Nursery practice pinches at four weeks to shape a young plant, or pinches to a stake when a taller specimen is wanted.
The form you want decides the cuts: aggressive growth for a hedge, vertical training for a trellis, or a full, bushy, overflowing plant for a pot. Traditionally bougainvillea is planted along trellises and fences, and in containers it is trained to a shrubbier shape. It also takes espalier, training as a standard, and a large basket. The standard, the small tree with a bare trunk and a head of color that turns up in courtyard photographs, is kept to size by spur pruning.
When to prune, month by month
Timing decides whether a cut costs you a flush or buys one.
Bougainvillea varieties worth knowing apart
Color is the easy half of the choice. Habit decides whether a plant covers a wall or fills a patio pot, and a few named forms trade the thorns or the plain green leaves for something else.
Light
Full sun is the requirement, and for bougainvillea that means six or more hours of direct light a day. The minimum for bloom is given two ways: six or more hours, or four hours of direct sun with bright light through the rest of the day. Light does more than keep the plant fed: high light intensity, moderate temperatures, and longer nights together bring flowering on sooner and more heavily, a combination that turns up in very early spring. Site the plant against a south or west wall with nothing shading it through the middle of the day, and use the one advantage a pot has, which is that it can follow the light through the season.
Water
Water deeply, then let the soil dry out before watering again. That one habit covers most of what bougainvillea asks for, in the ground and in a pot. The plant is extremely drought resistant once established and grows in almost any soil type that does not stay constantly wet, which is why it holds up in a hot bed next to lantana and other plants that resent a daily sprinkler. A container in full sun dries far faster than open ground, so the interval shortens in summer heat and stretches in cool weather, while the pattern stays the same: a thorough soak, then a real dry-down. Leaf drop is a signal that has to be read carefully, because it follows overwatering, underwatering, low light, and cold alike. Weigh the pot or push a finger into the mix before watering, because a soaked plant shedding leaves and a bone-dry one shedding leaves need opposite fixes.
Soil and feeding
Bougainvillea wants soil that drains and leans slightly acidic. The target is a pH of 5.5 to 6.0, or just over 6.0. Alkaline ground is where trouble starts, since chlorosis, the yellowing that spreads between the leaf veins, is a known problem for bougainvillea in alkaline soil. Heavy soil that holds water is the other failure, and the answer is drainage before fertility: a raised bed, a slope, or a container will do more for the plant than trying to improve a wet clay hole. Those fine roots are the part that fails first in soggy ground, so pick the site for how it drains after a long rain.
Feeding is where most gardeners overdo it. Most growers use a balanced slow-release or soluble fertilizer at a 1:1:1 ratio, something like 20-20-20 or 14-14-14. For a plant in the garden, a general-purpose 10-10-10 at half the labeled rate, once a month, in early spring and midsummer, is enough. Container plants take a balanced 5-5-5 or 10-10-10 diluted to half strength, applied when the growing season begins and again in early summer, or monthly through the season. All three schedules are deliberately weak on a plant that flowers better hungry. Yellowing on new growth points somewhere else, usually a magnesium or iron shortage, and a complete micronutrient blend or a chelated spray corrects it.
USDA hardiness
Bougainvillea is hardy outdoors in zones 9 through 11. The edges of that range are disputed: 9a through 11b for Bougainvillea glabra, 9b and 10 in warm-climate production guidance, and zone 10 as the band where it thrives, with zone 9 survivable only when the plant is protected. Zone 9 is where the disagreement lives, because that is the band in which an ordinary winter costs nothing and a hard one takes the top of the plant. The thermometer is a better guide than the map: substantial winter damage arrives when temperatures hit the mid to low twenties. A plant frozen back is usually still alive at the root, and the bill comes due in color, since flowering is greatly reduced for a year or two after a freeze takes the top growth. Whether it comes back every year therefore depends on which side of that line you garden: zones 10 and 11 never interrupt it, zone 9 costs you the top growth in a hard winter, and north of there it comes back only if it spent the winter indoors.
Height and spread
Bougainvillea as a group is listed at 15 to 40 feet tall and as wide. The species set the range: Bougainvillea glabra runs 10 to 20 feet tall and 6 to 10 feet wide, and Bougainvillea spectabilis 15 to 40 feet tall and about as wide again. Held back by a pot and a glasshouse roof, the same plants stay 13 to 26 feet tall and only 3 to 5 feet across. At the far end of the scale, a single glabra stem in a warm climate has been measured at 20 to 30 meters, roughly 60 to 100 feet. Those figures are what the plant does unchecked, and in an American garden the container, the yearly cut, or the winter usually stops it first.
Planting and support
Plant it once and disturb the roots as little as you can. Bougainvillea roots are sensitive to movement and disruption and may not recover if they are handled roughly, so the root ball goes into the hole intact, with no teasing and no scoring. If an established plant has to move, dig out as much of the root ball as the shovel will lift, since root loss is what the plant struggles to replace. Careful handling doubles as the root rot control, along with a broad-spectrum fungicide drench applied at planting or transplanting. Put the trellis, fence, or pergola up before the plant goes in, because a young cane is easy to guide and a thorny mature one fights back. On the coast its salt tolerance is rated two ways: high enough to make bougainvillea a standard choice for south Florida and other coastal regions, and only moderate, with the plant better placed a little further inland.
Thorns, skin, and pet safety
Bougainvillea does not appear on the ASPCA plant lists for dogs or cats in either direction: both alphabetical listings run straight from borage to boxwood, with nothing in the place the name would occupy. A missing entry means no rating exists, which is a different thing from a clearance. The documented hazard on this plant is mechanical. The leaves themselves are not toxic, but a prick from the thorns can bring on dermatitis, a rash that behaves like poison oak or poison ivy, with pain, itching, stinging or burning skin, blisters, a scaly rash, swelling, and sores. Thorns are listed among the plant's own recognized problems, which is why the siting rule is to keep it out of high-traffic areas where somebody would brush it in passing. A doorway, a narrow walk, and the edge of a play area are all the wrong place for it.
Propagation
Bougainvillea is grown from cuttings. In cultivation the plant is sterile, which leaves stem cuttings as the only practical route and explains why every named variety on the market is a piece of one original plant. It roots best from semi-hardwood cuttings five to nine nodes long. Those should root in four to six weeks, and faster over bottom heat at 15 C, about 50 F, though rooting can take anywhere from six to twelve weeks depending on the method. Layering in late winter or early spring is usually more effective, and a layered plant flowers in two to three years.
Pests and diseases
Bougainvillea is generally disease free, troubled mainly by whitefly, mealybug, aphid, and red spider mite. Fungal and bacterial leaf spots do occur, and scales join the insect list, mainly under glass. Where the plant lives changes which of them you meet: mealybug and scale are the indoor problems, while aphids are the common outdoor one. Slugs and snails turn up in a mild garden, and hand removal is the first control, with a labeled neem oil as the next option.
One pest carries the plant's name. The bougainvillea looper is a smooth-skinned caterpillar, yellowish or green to brown, up to an inch long, that moves the way an inchworm does, drawing its rear up to its head and then reaching forward. Young larvae feed on tender shoots and along leaf edges, leaving them scalloped, older larvae work on mature leaves, and a heavy infestation can strip a plant. Catching one in the act takes effort, since both the larvae and the fast-flying gray to brown adult moths, wingspan about an inch, are active at night. For treatment, Bacillus thuringiensis controls young loopers and may do little against mature ones, while spinosad works on both.
What actually goes wrong, ranked
Ordered by how often each one comes up across roughly four dozen bougainvillea threads on general gardening and bonsai forums, counted by thread title, so treat the ranking as approximate.
Symptoms: a patio plant brought inside sheds most of its leaves and sits bare for months, and the owner cannot tell a resting plant from a dead one. Management: growers split between forcing dormancy in a cool dim spot and running the plant as a bright houseplant, and the threads reach no agreement; pick one method for your space and hold it, and scratch a stem for green wood before writing the plant off.
Symptoms: leaves yellow and fall, usually on a potted plant, often within weeks of a move indoors or a change in the watering can. Management: the same symptom follows overwatering, underwatering, low light, and cold, so read the mix and the window before treating anything, and separate yellowing on old growth from yellowing on new.
Symptoms: a dark green, healthy plant with no color on it, in threads that usually describe careful watering and regular feeding. Management: the fix that works is the one that feels wrong, letting the plant go dry enough to droop before watering it again. Moving a rootbound plant into a bigger pot is the common first instinct, and it buys a season of stems.
Symptoms: after a freeze the plant is a bundle of gray sticks with no leaves and no obvious green. Management: scratch the bark, cut nothing yet, and wait for the base to push. Growers report recovery far more often than a real loss.
Symptoms: leaf edges chewed into scallops overnight, with nothing visible on the plant during the day. Management: hunt after dark with a flashlight, since the culprit feeds at night and hides by day. Daytime searches turn up nothing and send people looking for a disease that is not there.
Symptoms: a plant over the gutter and into the eaves, with an owner who does not know how far back is safe. Management: only a couple of threads in the sample are about pruning at all, and both are asking permission more than technique.
Symptoms: a puncture straight through a gardening glove, then a finger that stays stiff, red, and sore for days. Management: one long comment thread follows a welt and body-wide itching that ran for weeks and ended at a doctor's office. Treat a deep prick as a wound worth cleaning, and use leather gloves, since cloth does nothing.
Meaning and culture
Bougainvillea carries its formal meaning in the Caribbean, where it is the national flower of Grenada. The crest on that country's coat of arms, seven roses for its seven parishes, is set between two sprays of the plant. In the American trade it sells on sheer output, marketed as a flowering machine for the amount of color it turns out in a season. Everywhere else its meaning is associative: magenta over whitewashed stucco is shorthand for heat and coastline, which is where most Americans first meet one.
Myths about bougainvillea
This plant attracts more folklore than most, because the care that works on it looks like neglect.
The myth: Epsom salt makes it bloom.
The reality: The one documented use of Epsom salt on bougainvillea is a magnesium drench at one to two teaspoons per gallon for yellowing on old growth, a chlorosis treatment with nothing to do with flowering.
The myth: In a heat wave it needs more water to keep the color coming.
The reality: Extra water on a potted plant shows up as fewer flowers and fewer colorful bracts.
The myth: It is a houseplant that flowers on the windowsill all winter.
The reality: Winter is a rest period in every zone, with no feeding, and a plant held above freezing on fairly dry compost will drop its leaves.
The myth: Cutting it back hard will kill it.
The reality: Bougainvillea responds well to hard pruning, and only a very old, worn-out plant is better replaced than renovated.
What to expect, year by year
A bougainvillea does not arrive at full strength, and the first season is the one people misread.
Year one is roots and stems. A plant set in the ground grows rampantly and holds its flowers back for a couple of seasons while it settles in, and a container plant, with its roots confined, generally starts sooner. Pinch the tips early to build a branched framework, and expect a light, uneven show in the first summer.
By the second and third seasons the plant has enough wood to run on a cycle. Flushes come heaviest from spring into early summer and again from late summer into fall, with a cut after each one setting up the next. This is also when a borderline-zone plant earns its margin: once it is past the first winter or two it is big enough to take most winter damage and recover.
A mature plant blooms over a longer stretch of the year than a young one, and the work turns from coaxing to restraint. Size is held by cutting hard and by leaving the roots crowded, and the yearly rhythm settles into flush, cut, flush.
In the vase
Bougainvillea is barely a cut flower. Stems of bracts wilt and the floral axis bends within a few days, because vascular occlusion blocks the water supply to the flowers. Almost everything measured about them comes from postharvest research on treated bracts in refrigerated storage, so read these as laboratory figures.
Flower photos
FAQ
Why does my bougainvillea have leaves but no flowers?
Water first: too much of it, or roots sitting wet, will stop the plant blooming completely. Then light, since a partly shaded plant makes healthy dark green leaves and few or no flowers, and then the bag, because a high-nitrogen fertilizer buys foliage.
What should I feed a bougainvillea to make it bloom?
Less than you think. A balanced formula diluted to half strength, applied when the growing season begins and again in early summer, is the container standard. Overfertilizing adds growth and inhibits blooming.
Does Epsom salt make a bougainvillea bloom?
No. Its one documented use on this plant is a magnesium drench for chlorosis on old growth.
What month does bougainvillea bloom?
There is no single month. Outdoors the season runs spring through fall, and year-round in some places, with the heaviest flushes from spring to early summer and again from late summer to fall.
Can I leave a potted bougainvillea outside all winter?
Only where frost does not reach it, since the plant is frost sensitive and is grown as a container plant or an annual everywhere else. Indoors, a resting plant wants a night minimum near 50 F.
How far back can I cut a bougainvillea?
Hard. Plants respond well to hard pruning, with a very old, worn one the exception. The routine maintenance cut takes long spent growth back by half once the bracts have fallen.
Is bougainvillea poisonous to dogs or cats?
It has no entry at all on the ASPCA plant lists for dogs or cats, so no rating exists either way. The hazard on record is the thorns, which are listed among the plant's problems.
Is it better to grow bougainvillea in a pot or in the ground?
A pot brings flowers sooner, because restricting the roots discourages rampant growth and encourages flowering. In the ground it grows rampantly and is reluctant to bloom for a couple of years, then covers whatever you gave it to climb.
What is eating my bougainvillea leaves at night?
Most likely the bougainvillea looper, a caterpillar up to an inch long whose larvae and adult moths are both active after dark. Leaf edges chewed into scallops are its signature.
How do you grow bougainvillea from a cutting?
Take semi-hardwood cuttings five to nine nodes long. They should root in four to six weeks, or quicker over bottom heat at 15 C, about 50 F.
Is bougainvillea a vine, a bush, or a tree?
All three, depending on how it is cut. Left to itself it is a woody climber that has to be tied to a fence, wall, or pergola; in a container it is trained to a more shrub-like shape; and as a standard it is spur-pruned to hold the size of a small tree.
Interesting tips
- A container plant can go into the ground without its roots being touched at all. Cut the bottom out of the pot, set plant and container together in the hole, then slide the container up over the leaves while you backfill around the root ball.
- Bougainvillea glabra has working uses beyond the wall it covers: it is used as a botanical insecticide, and in Mexico an infusion of it is taken for gastrointestinal and respiratory complaints.
- Bougainvillea spectabilis contains pinitol, a compound with an insulin-like effect that has been studied for development as a diabetes treatment.
Related Guides & Flowers
Hibiscus
The other tropical that carries a Sun Belt garden through the heat, with big single flowers where bougainvillea has bracts.
Pink flowers
Where the magenta and rose shades of bougainvillea sit among the other pink garden plants.
Purple flowers
The purple end of the range, from deep-bracted bougainvillea to the purples on other garden plants.
Types of flowers
The full catalog of flowers grouped by kind, for readers browsing beyond the tropics.