Please try our next iteration of the Michigan Flora Online here. Beginning on February 1, 2023, will point to this new site.

The new site offers several benefits over the existing website, including real coordinate mapping, giving a clearer view of the density of documentation as well as more precision about plant distributions and their link to landforms. We will also have the ability to update species pages more regularly, both in terms of new collections and as more existing Michigan specimens are georeferenced. In addition, we have a better photo display, and offer indented keys.


1. Leaves all basal or nearly so; lip split down the middle on the upper side.

C. acaule

1. Leaves cauline; lip with a small opening only at the base.

2. Lip pale to deep yellow.

C. parviflorum

2. Lip variously white and purple.

3. The 3 sepals all distinct nearly to base; lip prolonged below to a blunt conical pouch, strongly marked throughout with purplish.

C. arietinum

3. The 2 lateral (or lower) sepals fused most or all of their length; lip smoothly rounded without conical prolongation below, entirely white outside or with extensive white areas.

4. Lip entirely white outside, up to 2.5 cm long; sepals and lateral petals greenish yellow; plants with 3–4 leaves crowded near middle of stem, sparingly puberulent.

C. candidum

4. Lip white, marked with pink or purple outside, 2.5–5 cm long; lateral petals and sepals white; plants with more leaves, the stem and leaves copiously hirsute.

C. reginae

All species found in Cypripedium

Cypripedium arietinumRAM'S HEAD LADY-SLIPPER 
Cypripedium candidumWHITE LADY-SLIPPER 
Cypripedium parviflorumYELLOW LADY-SLIPPER 


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. February 1, 2023.