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Swainsona formosa

Sturt's desert pea

Attracts Pollinators Drought Tolerant Container Friendly

Overview

Swainsona formosa is a prostrate, trailing annual or short-lived perennial of arid inland Australia, with soft, sprawling stems radiating 3-6 feet (0.9-1.8 m) from a central crown and rising only 4-12 inches (10-30 cm) above the ground. The grey-green leaves are pinnate, 2-6 inches (5-15 cm) long, divided into many rounded leaflets and covered in soft silvery hairs that reduce water loss. The flowers are large pea blooms 3-4 inches (8-10 cm) long, held in upright clusters of six or more, with blood-red petals and a raised glossy black boss at the base of the upright standard petal. Some forms carry red-and-cream or all-cream flowers. After flowering, slender pods 2-3 inches (5-7.5 cm) long form and split to release hard seeds that persist in the soil for years. The plant germinates after rain on sandy and gravelly desert soils and flowers within a few months. It is highly sensitive to root disturbance and damping-off fungi, which makes it short-lived and difficult to transplant.

Native Range

Swainsona formosa is native to the arid and semi-arid interior of Australia, across Western Australia, the Northern Territory, South Australia, Queensland, and inland New South Wales. It grows on sandy plains, gravelly rises, and clay flats that flood briefly after rain.

Suggested Uses

Grown as a container and raised-bed feature in hot, dry climates, and in arid native gardens where drainage is sharp. It is displayed in hanging baskets and tall pots that let the flowering stems trail. It is the floral emblem of South Australia and is grown for cut and display flowers.

How to Identify

Recognized by prostrate trailing stems and grey, silvery-haired pinnate leaves, topped by upright clusters of large pea flowers 3-4 inches (8-10 cm) long. The typical flower is blood-red with a raised glossy black boss at the base of the standard petal. The combination of a desert prostrate habit, silvery foliage, and large black-bossed red flowers separates it from other Australian peas.

Appearance

Size & Dimensions

Height4" - 1'

Width/Spread3' - 6'

Colors

Flower Colors

red

black

Foliage Colors

gray green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~10 weeks

Winter Spring

Flowers in spring after winter and spring rains, broadly August to November, with timing driven by rainfall in its arid range. In good seasons plants carpet desert flats with flowers. Pods follow within weeks and shed long-lived seed.

Detailed Descriptions

Flower Description

blood-red with black boss

Foliage Description

grey-green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 8-12 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 Range6.0 - 8.0(Neutral)

357912

Soil Types

sand rocky

Drainagewell drained

Water & Climate

Water Needs

Very Low

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Grows in full sun on sharply drained sandy or gravelly soil low in nutrients. It is highly prone to root and stem rot, so it is grown in deep containers or raised beds and watered sparingly at the base, keeping foliage dry. Seed is scarified and sown direct or raised in deep tube pots, as the long taproot is easily damaged by disturbance. Hot, dry, airy conditions suit it, while humidity and wet soil cause rapid collapse. The plant is short-lived, often lasting a single season, and is renewed from seed. Like other Swainsona spp., it can contain swainsonine, an alkaloid toxic to grazing animals.

Pruning

Spent flower clusters are removed to prolong flowering through the season. The trailing stems are otherwise left to sprawl, as the plant is short-lived and not shaped. Dead and rotting growth is cleared promptly to slow the spread of fungal rots.