Amerorchis rotundifolia (Banks) Hulten

Small round-leaved orchis

The genus Amerorchis was created by Hulten in 1968 to house this sole North American species, previously considered to a species of Orchis, hence the generic name. The specific epithet rotundifolia is the Latin meaning "round leaf," and refers to the rounded leaves of this species.

Photo courtesy of Emmett Judziewicz

DESCRIPTION: Plant glabrous, 10-25 cm tall, arising from a caudex of slender roots. Leaf solitary, basal, 5-10 cm long and 7-9 cm wide. Inflorescence a loose raceme 11-23 cm tall, 5-15 flowered. Sepals ovate-elliptic to ovate, 7-10 mm long and 5 mm wide, pink to pinkish white, rarely white; dorsal sepal connivent with petals to form a hood over the column. Petals 5-6 mm long and 2-3 mm wide, closely appressed to the dorsal sepal and colored as the sepals. Labellum tripartite, center lobe often bilobed at the terminus, 6-10 mm long and 3-8 mm wide, whitish pink to white and spotted with deep magenta; labellum with a 5 mm nectar spur projecting behind.

It is unlikely that this species could be confused with any other in the Wisconsin flora.

In Wisconsin, Amerorchis is found almost exclusively in White Cedar (Thuja occidentalis) and Larch (Larix laricina) bogs--which tend to be calcareous, and apparently has a distinct preference for calcareous substrate in other parts of its range.

June 5 to July 5.

To the best of my knowledge, no records exist for pollination of this species.

DISCUSSION: Fuller (1933) reports that the soil around the roots of Amerorchis in Wisconsin was found to be "minimalkaline." This species is extremely rare in Wisconsin, probably because it is at the extreme southern part of its distribution here.

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