Monday, July 26, 2010

Small Round-leaf Orchis (Amerorchis rotundifolia)

The Small Round-leaf Orchis was originally classified as Orchis rotundifolia since it is most closely related to that European genus, but was reclassified in 1968. It is the only species in the genus Amerorchis and has no other close North American relatives.

This plant ranges from Alaska through Canada to Greenland, and south into the United States into Montana and Wyoming and from Minnesota eastward to Maine. Sadly, it is not found in Washington state.  It prefers open woodlands and boggy areas.

The plant is reported to grow to 35 cm tall, though the plants we have seen have all been much shorter, the tallest about 18 cm. The delightful bird-like or angel-like flowers are about 1-1.5 cm tall with 10-15 flowers per plant.  The plant has a single round leaf at the base.

There are various color forms, including a pure white form, but we have seen only one of these varieties (see below) and they are quite rare. The usual form, however, is quite abundant in some locations and we have seen them by the thousands in one area.

We've found this orchid several times in British Columbia and Alberta. We saw it first in British Columbia off an access road where it was growing with Cypripedium parviflorum and Platanthera huronensis.  We've since seen it in the area of Edmonton, Alberta.

The other BC location is in Mount Robson Provincial Park, where it was growing just beyond the bridge south of the Kinney lake campground and along the lake and on the edge of the woods past the bridge and then again along the river in the Whitehorn campground and north to White Falls.

We've seen two color varieties of this species  the striped-lip form, Amerorchis rotundifolia fma. lineata, found on an orchid hunting trip near Edmonton with a friend, and the nearly white form, Amerorchis rotundifolia fma. wardii, with only some pale coloring on the lip, seen along the Berg Lake Trail in Mount Robson Provincial Park.

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