Dipodium atropurpureum, commonly known as the purple hyacinth orchid, is a mostly leafless mycoheterotrophic orchid that is endemic to New South Wales. In summer it has up to forty dark pinkish purple to reddish purple flowers with darker spots and blotches on a tall flowering stem.
Dipodium atropurpureum is a tuberous, perennial herb with leaves reduced to overlapping, greenish purple bracts about 15sigfig=1NaNsigfig=1 long and 12sigfig=1NaNsigfig=1 wide on the flowering stem. For most of the year, plants are dormant and have no above-ground presence. The flowering stem reaches to a height of NaNsigfig=2NaNsigfig=2 and appears between December and February. It bears between ten and forty dark pinkish purple to reddish purple flowers with darker spots and blotches, and NaNsigfig=1NaNsigfig=1 wide. The dorsal sepal is linear to elliptic, NaNsigfig=1NaNsigfig=1 long, about 5sigfig=1NaNsigfig=1 wide and the lateral sepals are a similar length but lance-shaped and slightly narrower. The petals are slightly shorter than the sepals and all are free from each other with their tips strongly curved backwards. The labellum is dark purplish red and projects forwards, NaNsigfig=1NaNsigfig=1 long, NaNsigfig=1NaNsigfig=1 wide with a narrow central band of mauve hairs up to 1sigfig=1NaNsigfig=1 long.[1] [2] [3]
Dipodium atropurpureum was first formally described in 1991 by Australian botanist David Jones and the description was published in Australian Orchid Research. The type specimen was collected east of Walcha in 1987. The specific epithet (atropurpureum) is derived from the Latin words ater meaning "black"[4] and purpura meaning "purple", referring to the dark purple flowers of this orchid.
The purple hyacinth orchid is common on the ranges between Kyogle and Wauchope in northern New South Wales where it grows in open forest with sparse low shrubs.
Pollination of this species, as for all species in the genus, is by native bees and wasps.
No leafless species of Dipodium has been sustained in cultivation due to the inability to replicate its association with mycorrhizal fungi in a horticultural context.