Shrub · Nyctaginaceae
Bougainvillea
Bougainvillea spectabilis
Give it scorching sun and lean, dry roots, and the woody stems crowd themselves with papery color.
Full sun
Every 7–14 days
USDA 9–11
15–40 ft · 4.6–12.2 m
Overview
Bougainvillea is the source of those sheets of color spilling over fences and arches in warm regions. The frame underneath is a woody, thorny shrub out of South America that can scramble and sprawl to 15 to 40 feet (4.6 to 12.2 m) where it is content, or stay knee-high in a container. The color is not petals at all but a dense crowd of papery bracts, thin and crinkled like tissue, which is why people call it paper flower.
The trick is that the bracts come thickest when the plant is a little starved. Rich soil, steady water, and a heavy feed grow you a leafy green bush with almost no color showing. Pull back instead, give the canopy fierce sun and lean, dry footing, and the papery color floods the stems from spring into fall.
Outdoors it survives only in USDA zones 9 to 11, where a killing frost almost never lands. In colder places it goes in a pot and comes under cover for winter, since it puts on growth quickly and shrugs off hard pruning. The thorns never leave, lining the woody stems in the leaf axils, so heavy gloves stay part of the work.
Care
The short version: all-day sun on the canopy, fast-draining soil at the roots, and a drink only after the top dries. Feed lightly with low nitrogen, cut it back after bloom, and shield the tender shoots from frost.
Light
The canopy wants full sun, at least 6 hours a day, and more only helps. Drop it into shade and the stems run to plain green leaves with no papery color, because it takes strong light to set bracts at all.
Water
Soak it deeply, then let the top of the soil dry before the next drink, which usually works out to every 7 to 14 days on an established plant. It handles drought and even colors up better kept on the dry side, while soil that never dries grows leaves in place of bracts and rots the roots.
Soil
Set it in well-drained sandy or loamy soil. It prefers a slightly acidic to neutral root zone, around 6.0 to 7.0, and the foliage suffers in ground that stays wet.
Temperature
Heat suits it, and it takes anything from about 30°F to 100°F (-1°C to 38°C) in stride. Freezing is the wall it cannot pass, since frozen tissue turns water-soaked and then black, so cover it or bring it in once cold threatens.
Humidity
Plain average air is enough, with no figure to chase. The plant cares far more about sun on its bracts and dry footing at the roots than about moisture around the leaves.
Feeding
Feed monthly from spring through midsummer using a balanced fertilizer at half the usual rate. Hold the nitrogen down, because a rich feed swells leafy growth and starves out the bracts you are growing it for.
Pruning
Cut it back in late winter or early spring after flowering, and leave any hard reduction until the bloom period closes. Keep heavy gloves on, since the spines in the leaf axils catch and tear.
Repotting
Move it up every 2 to 3 years or once it crowds the pot. A tight, slightly pot-bound root ball actually pushes more bracts, so there is no hurry to give it a bigger home.
Size & spacing
Turned loose, it climbs to 15 to 40 feet (4.6 to 12.2 m) tall with a spread to match, so a climbing specimen needs a solid wall or trellis to lean on. Penned in a pot it stays much smaller, and the dwarf cultivars are bred for cramped corners.
When to plant
This plant lives on heat and the soft new shoots blacken at a frost, so wait until spring has truly warmed before setting it out. Once warm, the bract clusters open from spring through fall and sometimes keep their color into winter where the cold never bites.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: after all danger of frost has passed in spring
- Harvest: spring through fall, sometimes into winter
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Trouble on a bougainvillea reads right off the plant itself: bare green stems with no papery color, or a sudden carpet of dropped leaves and bracts. Both point back to how it is grown rather than to disease. Look closely at the parts described below and match what you see before a small slip leaves you with a thorny, leafless frame.
A sudden carpet of fallen leaves and bracts
A sudden shed almost always trails a shock, usually a cold snap, a draft, or a move to a new spot. Frozen leaves and tender shoots go water-soaked first and then turn black. Hold it in one steady, warm, sunny place, water on an even rhythm, and bring pots indoors before the air slides toward 30°F (-1°C).
Fix:
- Protect from frost and bring containers indoors before temperatures fall below about 30 degrees F
- Keep the plant in a stable location and avoid moving it
- Maintain consistent watering, avoiding both drought and waterlogging
Leaves gone yellow while the veins stay green
When the newest leaves pale to yellow but the veins hold their green, the roots cannot pull up enough micronutrients, usually because the soil runs too alkaline or sits wet too long. Keep it in slightly acidic, fast-draining ground and let the soil dry between drinks. A foliar micronutrient spray made for citrus or palms brings the green back.
Fix:
- Maintain slightly acidic, well-drained soil
- Apply a foliar micronutrient spray suitable for citrus or palms
- Improve drainage and avoid keeping soil constantly wet
Plenty of green leaves, hardly any color
Bare green stems with no papery bracts nearly always mean the plant has it too easy. Bougainvillea sets color under stress, so trim back the water, push it into at least 6 hours of full sun, and cut the nitrogen. A touch of drought, even a root ball that is a little cramped, tips it into flowering.
Fix:
- Move to or provide full sun (6 or more hours direct)
- Allow soil to dry out between deep waterings and reduce watering
- Stop high-nitrogen feeding; use a balanced fertilizer at a reduced rate
- Allow the plant to become slightly pot-bound or stressed to encourage blooming
Leaf edges notched and scalloped, dark droppings below
This is the bougainvillea looper, a green-to-brown inchworm-like caterpillar that chews the leaf margins after dark and leaves them scalloped. Catch it in the act with a night check, then pick the caterpillars off by hand. For a worse outbreak, hit young larvae with Bt or use spinosad, which clears both young and grown caterpillars.
Fix:
- Handpick caterpillars, checking at night when they feed
- Apply Bacillus thuringiensis (Bt) to control young larvae
- Apply spinosad, which controls both young and mature larvae
Toxicity
There is no toxin in any part of this plant, so a nibbled leaf will not poison a cat, dog, or grazing animal. The danger is built into the stems themselves. Stiff, sharp thorns sit in the leaf axils and drive in like needles, leaving punctures, scratches, and sometimes dermatitis, while the thin sap can sting sensitive skin, so pull on heavy gloves before you touch it.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
There is no toxic compound in the tissue, so a curious cat is not poisoned by a taste. The hazard is the stiff thorns, which can rake a paw or a face, so set a potted plant clear of where a cat tends to leap.
Dogs None
A dog is safe around bougainvillea, and a chewed leaf will not poison it. Pushing through the canopy can snag a thorn, though, so watch for the odd scratch or puncture rather than any illness.
Horses Safe
Grazing the plant does a horse no harm. The sharp spines are the only worry, since a horse leaning into the branches can take a puncture.
Rabbits Safe
A rabbit can eat the leaves with no risk of poisoning. Keep the thorny stems off a small animal, where a spine could badly hurt soft skin or an eye.
Livestock Safe
Cattle, goats, and sheep meet no toxin in the plant. The woody thorns are what to watch, since they can scratch hide or muzzle as the animals browse the growth.
Birds Safe
Birds perch and nest in bougainvillea unharmed, with no toxin in play. The thick, spiny stems even hand small birds a sheltered place to hide.
People Safe
The plant poisons no one, but the thorns will get you. Their punctures and scratches can turn to dermatitis or, rarely, a skin infection, and the thin sap may sting sensitive skin, so keep heavy gloves on whenever you prune or handle it.
Not chemically poisonous, but the plant has sharp woody thorns/spines that cause puncture wounds and scratches (rarely skin infection or dermatitis), and the sap may cause mild skin irritation in sensitive people. The physical thorns are the real hazard, not chemical poisoning. Wear heavy gloves when pruning or handling.
Varieties
The named forms split mostly by bract color and by how big the woody frame gets, from sprawling climbers to tidy dwarfs sized for a pot. These are the ones you are most likely to meet.
Barbara Karst
A fast, strong grower that loads its stems with deep red to magenta bracts in heavy waves.
San Diego Red
A large, well-known red form valued for the sheer weight of bracts it carries.
Raspberry Ice
A compact form whose variegated green-and-cream foliage sits beneath rose-red bracts.
California Gold
Marked out by warm yellow to gold bracts in place of the usual pinks and reds.
Pixie
A dwarf, naturally tight grower that settles neatly into a container.
Helen Johnson
A dwarf, compact form that takes well to pots and hanging baskets.
How to propagate
Multiplying a bougainvillea takes patience more than skill, and a piece cut from a plant you already grow will copy its bract color far more reliably than a seed ever will.
Stem cuttingsModerate
Summer · Several weeks to a few months
The common route is a cutting taken in summer. Snip a length of this season's growth, push it into a sand and peat mix, and wait, because roots can take anywhere from a few weeks to a few months to break.
LayeringModerate
Growing season · Several weeks to months
You can also layer it through the growing season, pinning a low stem to the soil so it roots while still joined to the parent. Several weeks to months pass before that section holds enough root to cut loose.
SeedDemanding
Warm season · Slow and variable
Seed will sprout in the warm season but the process is slow and erratic, and seedlings seldom copy the parent. For that reason the named cultivars almost always come from cuttings or layers.
Myths
The bright papery parts of a bougainvillea are its flowers.
Those thin colored leaves are modified leaves called bracts, not flowers. The true flowers are the small white or cream tubes sitting at the center of each cluster, slim and easy to overlook against all that surrounding color.