America's Orchids - Small Roundleaved Orchis

Small roundleaved orchis (Amerorchis rotundifolia) is sometimes called one-leaf orchis and roundleaf orchis. This North American native plant can have as many as 15 small flowers on a single raceme. The pink buds open to become flowers that are white to soft pink to pale purple with deep rose polka dots on the lower, three-lobed petal. The flowers appear from May until August, depending on the area, in the northern most tier of the United States and throughout Canada.

Roundleaf orchis is a small plant and grows to a height of only 4 to 12 inches. Look for them in open wetlands such as swamps, bogs, moors, fens, and the tundra. They prefer acidic, moist soil with a chalky and lime substrate. They grow in full sun or light shade. They are not tolerant of competition for the minimal soil nutrients found in wetland areas and will be crowded out when seed does not germinate readily.

Roundleaf orchis can also be found growing in coniferous forests that are comprised mainly of balsam fir, black spruce, and white cedar.

Roundleaf orchis is found more often in lowland areas fed by a very cold groundwater source. The plant distribution will be impacted by warming trends either from clear-cutting of the surrounding tree canopy or changes in climatic conditions that affect predominant water and air temperatures.

Roundleaf orchis has a single leaf that measures 2 to 4 inches. The yellowish-green leaf grows at ground level, and is both oval and lustrous. A single stem rises from the plant with the flowers clustered toward the upper tip. A single flower petal is 1/4 inch long and 1/8 inch wide and the tri-lobed petal is slightly larger.

Roundleaf orchis can sometimes be found growing in the wild with Ledum groenlandicum (Labrador tea), Listera cordata (heart-leaved twayblade), Malaxis unifolia (green adder's-mouth), bulrush (Scirpus hudsonianus), alder-leaved buckthorn (Rhamnus alnifolia), yellow lady's-slipper orchid (Cypripedium calceolus), flat-topped aster (Aster umbellatus), Platanthera obtusata (blunt-leaf orchid), Smilacina trifolia (false Solomon-seal), and Cypripedium reginae (showy lady's slipper).

Roundleaf orchis is listed as endangered or threatened in the northeastern US. The orchid is quite common in the western states. The roundleaf orchis propagates by self-seeding. The plant is found growing in colonies in the western areas. The close proximity of the plants can sometimes disguise the single-leaf habit.

It is illegal in most areas to pick or collect wildflowers. There are some nurseries that specialize in rare orchids. The Orchid Mall maintains a list of potential orchid vendors organized by country.

Orchids growing in the wild are also subjected to foot traffic that can disturb the delicate wetland ecosystem. A program in Michigan in the Hiawatha National Forest, involves the identification and monitoring of the remaining colonies of roundleaf orchis. The ongoing research may find ways that both roundleaf orchis and their fen home can be preserved.

Sources

Amerorchis rotundifolia, http://www.orchids.org/ooc/Genera/Amerorchis/rotundifolia/
Amerorchis rotundifolia, USDA, http://plants.usda.gov/java/profile?symbol=AMRO
Amerorchis rotundifolia, Lady Bird Johnson Wildflower Center, http://www.wildflower.org/plants/result.php?id_plant=AMRO
Amerorchis rotundifolia, Robert W. Freckmann Herbarium, University of Wisconsin, http://wisplants.uwsp.edu/scripts/detail.asp?SpCode=AMEROT
Amerorchis rotundifolia, University of Wisconsin, http://www.botany.wisc.edu/orchids/Amerorchis.html
Amerorchis rotundifolia, Michigan Natural Features Inventory, http://web4.msue.msu.edu/mnfi/abstracts/botany/Amerorchis_rotundifolia.pdf
Orchid Mall, http://www.orchidmall.com/plants.htm
Celebrating Wildflowers, US Forest Service, http://www.fs.fed.us/wildflowers/rareplants/conservation/success/amerorchis_rotundifolia_conservation.shtml