Alstonia spp.

Tropical Africa, Asia, northern Australia, and the Pacific

SunFull Sun – Part Shade

HardinessZones 10–12

Overview

Alstonia spp. is a genus of about 40 to 60 evergreen trees and shrubs in the family Apocynaceae, spread through the lowland tropics of Africa, Asia, northern Australia, and the Pacific. Most species reach 10-40 m (33-130 ft), with tiered, horizontal branches and a layered crown; all parts exude a milky white latex when cut. The leaves are leathery and arranged in whorls of three to ten around the stem, 5-25 cm (2-10 in) long, with many close, parallel side veins. Clusters of small tubular flowers, white to greenish-cream, open at the branch tips and carry a heavy scent, often strongest at night. Each pollinated flower forms a pair of long, slender follicles 20-60 cm (8-24 in) long that split to release flat seeds fringed with silky hairs for wind dispersal. Alstonia spp. grows in rainforest, monsoon forest, and swamp margins and does not tolerate frost. The pale, even-grained wood of A. scholaris has been used for blackboards, carving, and light timber. The latex and bark are bitter and have a long record of use in traditional medicine.

Native Range

Native to the lowland tropics of Africa, South and Southeast Asia, northern Australia, and the Pacific, growing in rainforest, monsoon forest, and along swampy margins.

Suggested Uses

Grown as shade, avenue, and specimen trees in tropical parks and large gardens, and used in their native regions for light timber and medicinal bark and latex. The strong night scent makes several species common near temples and roadsides.

How to Identify

Recognized by leaves arranged in whorls around the stem, each leathery and marked with many close, parallel side veins, and by the milky latex that flows from any cut surface. Clusters of small white to greenish tubular flowers smell strongly, mainly at night. The fruit is a pair of very long, slender follicles 20-60 cm (8-24 in) long.

Appearance

Size & Dimensions

Height32'10" - 131'3"

Width/Spread16'5" - 49'3"

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~6 weeks

Fall

Clusters of small tubular white to greenish flowers open mainly in the warm, wet months, with timing varying across the genus wide range. The scent is heavy and carries furthest at night, drawing moths. Long paired follicles develop over several months and split to shed plumed seeds.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 5-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

loam clay sand

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

tender

Time to Maturity

10-25 years

Care & Maintenance

Care Guide

Most species grow in full sun to part shade on moist, deep, well-drained soils in frost-free climates. Steady warmth and reliable moisture support fast growth and the tiered branching habit. Plants exude latex from any wound and resprout after damage. They are damaged or killed by frost and are grown under glass outside the tropics. The seeds are short-lived and germinate readily when fresh.

Pruning

Little pruning is needed beyond shaping young trees and removing lower or crossing limbs. Cuts bleed latex, which seals the wound as it dries. Plants tolerate crown reduction in warm weather and regrow from the cut points.

⚠️ Toxicity Warning

Toxic to pets and humans

Trees

Alstonia spp.

Apocynaceae

Tropical Africa, Asia, northern Australia, and the Pacific

Attracts Pollinators Fragrant (strong)

SunFull Sun – Part Shade

WaterMedium

HardinessZones 10–12

Overview

Native Range

Native to the lowland tropics of Africa, South and Southeast Asia, northern Australia, and the Pacific, growing in rainforest, monsoon forest, and along swampy margins.