Petalostigma spp.

Picrodendraceae Australia and southern New Guinea

SunFull Sun – Part Shade

HardinessZones 10–11

Overview

Petalostigma spp. is a small genus of shrubs and small trees in the family Picrodendraceae, native to Australia and southern New Guinea and known as quinine bushes or bitterbarks for their bitter wood and fruit. Plants grow as dense shrubs or small trees 6-26 feet (2-8 m) tall, with rough or corky bark and alternate, leathery leaves that are dark green above and often rusty-hairy or pale beneath. The genus is dioecious, with separate male and female plants bearing small, petalless, greenish-yellow flowers in the leaf axils. Female plants develop hard, woody, orange to red capsules that split open forcefully when dry, flinging the seeds some distance from the plant. The bitter bark and fruit have a history of use in Aboriginal bush medicine. Petalostigma spp. grows in open forest, woodland, and scrub on sandy or gravelly soils across northern and eastern Australia, tolerating heat, drought, and seasonal dry periods. The genus is fire-tolerant and resprouts from the base and roots after burning, sometimes forming thickets through root suckering. Plants need sharp drainage and full sun and are slow-growing in cultivation. The hard, long-persistent fruit and rough bark give the shrubs a rugged appearance through the year.

Native Range

Petalostigma spp. is native to Australia and the savannas of southern New Guinea, ranging widely across northern, eastern, and central Australia. Plants grow in open eucalypt forest, woodland, and scrub on sandy and gravelly soils.

Suggested Uses

Petalostigma spp. is grown in Australian native and dryland gardens, in habitat and revegetation plantings, and as an informal screen on poor soils. The persistent colored fruit and drought tolerance suit low-water and wildlife gardens in warm climates.

How to Identify

Look for dense shrubs or small trees with leathery leaves that are dark green above and paler or rusty beneath, on rough or corky bark. Male and female plants are separate, and female plants carry hard, woody orange to red capsules that split open when dry. The bitter bark and woody, forcibly splitting fruit identify the quinine bushes.

Appearance

Size & Dimensions

Height6' - 26'

Width/Spread6' - 20'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~8 weeks

Spring Summer

Flowering occurs mainly in spring and early summer, with small greenish-yellow petalless flowers borne in the leaf axils. Male and female flowers are on separate plants, so only female plants set fruit. The hard capsules ripen to orange or red and persist on female plants for months.

Detailed Descriptions

Foliage Description

dark green above, paler beneath

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 - 7.0(Neutral)

357912

Soil Types

sand rocky loam

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

tender

Time to Maturity

4-8 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Petalostigma spp. grows in full sun to light shade on sandy or gravelly, sharply drained soil and tolerates heat, drought, and long dry seasons. The genus is fire-tolerant and resprouts from the base and roots after burning, sometimes suckering into thickets. Plants are slow-growing and need good drainage, declining in wet or heavy soils. Both male and female plants are needed for fruit to set. Few pests trouble the tough, leathery foliage. Established plants need little water or care in a suitable warm, dry climate.

Pruning

Light pruning after flowering shapes shrubby plants and removes dead wood. Plants tolerate harder cutting back because they resprout from the base. Root suckers can be removed to limit spread into thickets.