Bougainvillea

Bougainvillea glabra is native to Brazil, where it grows in the Atlantic Forest region and other tropical to subtropical habitats. It was discovered by European explorers in the 18th century.

• Named in honor of Louis Antoine de Bougainville (1729–1811), the French navigator and military commander who led the first French circumnavigation of the globe (1766–1769)
• The plant was discovered in Brazil in 1768 by Philibert Commerçon, the naturalist aboard Bougainville's expedition — though it may actually have been discovered by Commerçon's assistant (and disguised lover) Jeanne Baret, the first woman to circumnavigate the globe
• The species name glabra means "smooth" or "hairless," referring to the relatively smooth leaves and stems (compared to other Bougainvillea species)
• Introduced to European horticulture in the early 19th century and quickly became a prized greenhouse and conservatory plant
• By the 20th century, bougainvillea had been planted throughout the tropics and subtropics and had become one of the most recognizable ornamental plants in the world
• The genus Bougainvillea contains approximately 18 species native to South America
• The vivid "petals" are actually bracts — modified leaves that have evolved to attract pollinators to the tiny true flowers they surround
• Modern cultivar breeding has produced an enormous range of colors, double-flowered forms, and variegated foliage
• Bougainvillea is the national flower of Grenada and the state flower of Guam
• Widely planted along the Mediterranean coast, in India, Southeast Asia, Australia, and the Americas

Bougainvillea is a vigorous, thorny, woody evergreen vine climbing 5–10+ m by scrambling over supports, with long, arching canes armed with sharp thorns.

Stems: Long, arching, woody canes armed with sharp, curved thorns 0.5–1.5 cm long. Young stems are green; mature bark is gray-brown. The thorns (technically modified stipules) are curved downward and help the vine scramble through vegetation.

Leaves: Alternate, ovate to elliptic, 5–10 cm long and 2.5–5 cm wide, dark green, smooth, with smooth margins. Some cultivars have variegated foliage.

Flowers: The spectacular display consists of: (1) BRACTS — the large, showy, papery-thin, intensely colored modified leaves, typically in clusters of 3 surrounding each true flower. Bracts are 2–4 cm long, in brilliant shades of magenta-purple, crimson-red, orange, pink, or white depending on cultivar. The bracts persist for weeks to months. (2) TRUE FLOWERS — tiny, tubular, waxy, cream-white to yellowish flowers, 1–2 cm long, emerging from the center of the bract cluster. Individually inconspicuous, but the overall effect of bracts plus flowers is spectacular.

Fruit: Small, dry, 5-angled achenes. Rarely produced in cultivation.

Roots: Extensive, deep root system. The plant is very drought-tolerant once established.

Bougainvillea grows naturally in the tropical and subtropical forests of Brazil, where it scrambles through vegetation in warm, seasonally dry conditions.

• Thrives in full sun and heat — the more sun, the more bloom
• Extremely drought-tolerant — actually blooms best when slightly stressed (underwatered)
• Prefers well-drained, even rocky or sandy soils — excellent drainage is essential
• Tolerates salt spray — widely planted in coastal gardens
• The brilliant bracts attract butterflies and hummingbirds to the tiny true flowers within
• In cultivation, the plant is extremely versatile — grown as a vine on walls and pergolas, shaped as a shrub, trained as a tree standard, or even as a bonsai
• Overwatering and excess nitrogen promote leafy growth at the expense of bloom
• The sharp thorns make bougainvillea an effective security barrier when planted under windows or along fence lines
• Generally pest and disease-free in good cultural conditions
• Can be damaged by frost — prolonged temperatures below -2°C cause damage
• Has naturalized in many tropical and subtropical regions but is not generally considered a serious invasive species
• The plant responds to stress (drought, root restriction) by producing more flowers

Bougainvillea is one of the most dramatic and rewarding vines for warm-climate gardens, but it has specific cultural requirements.

Light: Full sun — absolutely essential. Needs at least 6–8 hours of direct, intense sun daily. Will not bloom well in shade or even light shade.

Soil: Well-drained soil — the most critical requirement. Tolerates poor, sandy, rocky, and alkaline soils. pH 5.5–7.0. Will rot in heavy, wet, poorly drained soils.

Planting: Plant container-grown plants in spring or summer. Space 1.5–3 m apart. Do not disturb the root ball — bougainvillea resents root disturbance. Handle gently during transplanting.

Watering: This is the key to bougainvillea success — water deeply, then allow the soil to dry out significantly before watering again. Overwatering produces lush green foliage but no flowers. Underwatering slightly (wilting) triggers bloom. Once established, bougainvillea is extremely drought-tolerant.

Fertilization: Minimal — avoid excess nitrogen. Use a bloom-boosting fertilizer (higher phosphorus and potassium) sparingly in spring and summer. No fertilizer in fall and winter.

Pruning: Prune after each bloom cycle. Cut back long canes by up to half. Remove dead wood and shape as desired. Can be pruned hard — the plant regrows rapidly. Wear thick gloves to protect against thorns.

Container Growing: Excellent in containers — root restriction promotes flowering. Use a well-draining potting mix. Allow to dry between waterings.

Hardiness: USDA Zones 9–11. Damaged below -2°C. In Zone 8, grow in containers and move indoors for winter. Root-hardy to about -7°C with heavy mulch.

Propagation: By semi-hardwood cuttings in summer (use rooting hormone). Can also be propagated by air layering.