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Cyrtostylis robusta

large gnat-orchid

Orchidaceae Southern Australia

Attracts Pollinators Container Friendly

SunPart Shade – Full Shade

WaterLow

HardinessZones 9–10

Overview

Cyrtostylis robusta is a small terrestrial orchid in the family Orchidaceae, growing from an underground tuber and producing a single flat, heart- to kidney-shaped basal leaf 0.8-2 inches (2-5 cm) long that lies close to the ground, green above and often reddish beneath. A slender flowering stem 4-10 inches (10-25 cm) tall carries two to ten small reddish to pinkish flowers, each about 0.4-0.6 inch (10-15 mm) across, with narrow, spreading sepals and petals and a broad, flat labellum. Flowering occurs in autumn and winter. The flowers are pollinated by small fungus gnats drawn to them. The plant grows in southern Australia in coastal scrub, mallee, and open woodland on sandy soils, often forming colonies through tuber division. After flowering and seed set, the leaf and stem die back and the plant survives the dry summer as a dormant tuber. In cultivation it requires a free-draining sandy mix, moisture through the cool growing season, and a dry summer rest. The tuber rots in soil that stays wet over summer. Colonies build slowly as tubers multiply underground.

Native Range

Cyrtostylis robusta occurs in southern Australia, including South Australia, Victoria, Tasmania, and southern Western Australia. It grows in coastal scrub, mallee, and open woodland on sandy soils, often forming colonies.

Suggested Uses

Grown by terrestrial orchid enthusiasts in pots and protected garden pockets. Suited to native orchid collections and shaded, free-draining bush-garden settings. Shown in colonies where the small flowers are visible together.

How to Identify

Identify Cyrtostylis robusta by its single flat, heart- to kidney-shaped basal leaf 0.8-2 inches (2-5 cm) long lying close to the ground, often reddish beneath. A slender stem 4-10 inches (10-25 cm) tall carries two to ten small reddish flowers with narrow, spreading segments and a broad flat labellum. Autumn and winter flowering and the larger flowers separate it from the smaller, spring-flowering Cyrtostylis reniformis.

Appearance

Size & Dimensions

Height4" - 10"

Width/Spread2" - 4"

Colors

Flower Colors

red

pink

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~6 weeks

Fall Winter

Flowering occurs in autumn and winter, around April to July in its native range. The slender stem carries two to ten small reddish to pinkish flowers with spreading segments. Flowers are pollinated by small fungus gnats.

Detailed Descriptions

Flower Description

reddish to pink

Foliage Description

green, reddish beneath

Growing Conditions

Sun Requirements

SunPartial Shade SunFull Shade

Tolerates up to 4 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 loam

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

2-4 years

Care & Maintenance

Care Guide

Grow Cyrtostylis robusta in a free-draining sandy terrestrial orchid mix in dappled shade to part sun. The mix is held lightly moist through the autumn-to-spring growing season, then water is withheld during summer dormancy. The tuber rots in soil that stays wet over summer. Cool, frost-free to lightly frosted conditions suit active growth. A light leaf-litter topdressing applied each autumn supports growth as it resumes. Pots are left undisturbed for several seasons to let colonies build.

Pruning

Spent flowering stems are removed after seed set where self-seeding is not wanted. Cyrtostylis robusta dies back naturally to its tuber, so no foliage pruning is needed. Dead growth is cleared before the next season begins.