Microtis arenaria
pale onion-orchid
Overview
Microtis arenaria is a terrestrial orchid that grows from an underground tuber and produces a single hollow, onion-like leaf 8-16 inches (20-40 cm) long, which sheaths the lower part of the flowering stem. The slender flower spike stands 6-16 inches (15-40 cm) tall and carries 10 to 50 small green flowers along its upper third. Each flower is about 0.1-0.2 inch (3-5 mm) across, with a hooded dorsal sepal arching over a down-curved labellum that has a notched tip. The plant is dormant through the dry months and reappears after autumn and winter rains, with flowering following in late spring and summer. It grows in sandy soils of coastal heath, woodland, and seasonally damp flats across southern and eastern Australia. Pollination is carried out by ants and small insects, and the flowers can also self-pollinate, so seed set is usually high. After seed release the leaf and stem wither back to the tuber, leaving no growth above ground until the next season. The green flowers blend into surrounding vegetation and are hard to see when the plant is not in full bloom. Tubers increase slowly, forming loose colonies in undisturbed sandy ground over several seasons.
Native Range
Microtis arenaria is native to southern and eastern Australia, including Victoria, New South Wales, South Australia, Tasmania, and Western Australia. It grows in sandy soils of coastal heath, open woodland, and seasonally moist flats.Suggested Uses
Microtis arenaria is grown by native-orchid growers in deep pots and is included in the ground layer of restored sandy heath and woodland. It suits undisturbed native garden beds where the summer-dormant tuber is not dug or watered.How to Identify
Appearance
Size & Dimensions
Height6" - 1'4"
Width/Spread2" - 4"
Reaches mature size in approximately 3 years
Bloom Information
Flowering runs from late spring into summer, roughly October to January in its native range. The small green flowers open in sequence from the base of the spike upward over two to four weeks. Flowering is heavier in seasons that follow good autumn and winter rainfall.
Detailed Descriptions
Foliage Description
greenGrowing Conditions
Sun Requirements
Requires 4-8 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
Care & Maintenance
Care Guide
Microtis arenaria grows from a tuber that needs a dry, warm dormancy once the foliage dies back in summer. It grows in a free-draining sandy mix kept moist through the autumn-to-spring growing period and left dry during dormancy. Like other terrestrial orchids it relies on soil mycorrhizal fungi, and seed germination depends on these fungi being present. In containers it is grown in deep pots that hold the tuber below the surface and drain freely. It grows in full sun to light shade. Tubers rot if the mix stays wet while the plant is dormant.Pruning
Pruning does not apply to this terrestrial orchid. The spent flower spike can be removed after seed has shed, and the leaf is left to die back on its own so the tuber can recharge for the next season.Container Growing
✓ Suitable for container growing
Minimum container size: 1 gallons