Common name: Stephenson's midge orchid
Genoplesium stephensonii (D.L.Jones) J.M.H.Shaw APNI*
Synonyms: Corunastylis stephensonii D.L.Jones APNI*
Description: Terrestrial tuberous herb.
Leaf terete, 10–18 cm long, 1.0 mm wide, base reddish; free lamina linear-lanceolate 10–15 mm long, 2.0 mm wide, ending just below the first flower.
Inflorescence 11–20 cm tall, bearing 1–5(-8) flowers in a closely set, but not congested or crowded, spike 8–15 mm tall. Flowers deflexed, 5.5 mm wide, green with pink to reddish markings and hairs. Dorsal sepal ovate lanceolate with an acuminate apex, 4.5–5.0 mm long by 3.5 mm wide, concave, margins entire, pale purple or purple-green with 5 darker purple medial and marginal stripes. Lateral sepals narrowly triangular-falcate, 5.0–5.5 mm long by 1.5 mm wide, ascendant in outer two thirds when fully opened, margins inrolled in the outer half to two thirds, apex obtuse; green with a red base. Petals lanceolate, 4.3–5.0 mm long by 1.5 mm wide, margins entire or with a few short hairs toward the base, apex acuminate; pale with red margins and three medial red stripes. Labellum hinged by a short claw, not mobile, ovate (in protologue) to elliptic (other individuals from West Nowra), semi-deflexed and evenly curved along its most of its length but with sharp curvature at the apex, 4.3 mm long by 2.6 mm wide, margins with numerous short spreading pink to purplish cilia 0.3–0.6 mm long, apex acute (protologue) to acuminate (other individuals from West Nowra); callus dark red, thickest and broadest just above the base then tapered to the apex, extending to (protologue) or close to (other individuals from West Nowra) the labellum apex. Column 2 (protologue)-2.5(other individuals from West Nowra) mm tall by 1.2 mm wide, pale or with reddish wash; wings deeply notched, lobes unequal; lower lobe falcate and attenuate with an acuminate apex, with red wash, the lower margin below the sinus slightly dilated, margins bearing closely set cilia that increase in length toward the middle of the lobe then decrease in length toward the apex, curved, purplish, with margins bearing dense short and irregular cilia; upper lobe ligulate with an obtuse to rounded apex, pale, entire, shorter (protologue and other individuals from West Nowra) to equal (other individuals from West Nowra) in length to the lower lobe. Stigma ovate-elliptic 0.8 mm long and 0.5 mm wide.
Flowering: Flowering recorded from November through to February.
Distribution and occurrence: In the vicinity of Nowra, extending south into Jervis Bay National Park and west to Sassafrass Hill.
In shallow well-drained sandy loam over sandstone pavements, and in sandy loam within low stature open woodland, often under tall Kunzea.
NSW subdivisions: SC
Genoplesium stephensonii is a member of the G. archeri complex, and can be recognised by the combination of 1) ciliate labellum margins, 2) entire petal and dorsal sepal margins; 3) the attenuate apex of the lower column arm lobe (where lower is defined by the floral axis – this lobe is described by Jones as the anterior lobe); 4) the few flowered inflorescences, usually with a maximum of 8 flowers.
Text by David L. Jones, with modification by Matt A.M. Renner (2 February 2021)
Taxon concept: Jones DL (2013) Corunastylis stephensonii, a new orchid species from the Shoalhaven Region of south-eastern New South Wales. Australian Orchid Review 78: 51-54.
APNI* Provides a link to the Australian Plant Name Index (hosted by the Australian National Botanic Gardens) for comprehensive bibliographic data
***The AVH map option provides a detailed interactive Australia wide distribution map drawn from collections held by all major Australian herbaria participating in the Australian Virtual Herbarium project.