This terrestrial orchid has a confused and confusing nomenclatural history (see wikipedia), but it is a beautiful and relatively easy subject for the warm greenhouse or, possibly, a sunny windowsill.
Cynorkis angustipetala is from Madagascar and is a member of the subtribe Habenariinae, which also includes our native Platanthera orchids:
In common with most of the tropical Habenariinae, C. angustipetala requires a dry winter dormancy when the foliage completely dies away, and the plant consists of a sausage-shaped tuber buried in the potting mix. C. angustifolia is one of the earliest of this group to break dormancy, and it will often start growing before I begin watering in the spring. My plants are currently blooming, while their relatives Habenaria rhodocheila and Pecteilis hawkesiana have yet to reveal whether they survived this year’s dormancy.
Potting mix can either be long fibered sphagnum or (my favorite) a 50/50 mix of sphagnum peat moss and perlite. Beware of perlite that has added fertilizer, because most terrestrial orchids react poorly to over-fertilization. In case any manufacturers read this: Hey! Stop putting fertilizer in perlite! The whole point of perlite is that it is inert.
Keep the mix constantly moist from early April until the foliage starts to yellow, probably in September or October, and do not water at all over the winter. If you are concerned about accidentally watering the pot (or over-drying the tuber in low humidity), you can seal the pot in a ziploc bag. Store the bag indoors in a dark place, because direct sunlight will cook the enclosed tubers.