The white flowers of Holothrix orthoceras grow from a leafless, but hairy, purplish scape. The slender flower spike becomes about 15 cm long, bearing up to 20 flowers. The inflorescence is not cylindrical; all the flowers face in roughly one direction (secund).
The pale green ovary angled upwards, curves away from the stem. The sepals are small, ovate with acutely pointed tips and coloured green and purple. The lateral petals angling up and outwards are small and narrow, white in colour.
The five-lobed lip, the main feature of the flower, becomes about 6 mm long, the lobes on the sides shorter than the central three. The lobes all have rounded to pointed tips. Dark, purplish markings on the lip surface run part of the way along the lines where the lobes are joined to each other.
The white spur is short, cylindrical and nearly straight. The specific name, orthoceras, is derived from Greek, meaning straight horn, probably referring to the spur.
Flowering happens during autumn (Germishuizen and Fabian, 1982; Gledhill, 1981; iSpot).