There are two varieties of what is called the Greater Yellow Lady's-slipper and they are similar in character. The second variety - Cypripedium parviflorum Salisb. var. pubescens has larger flowers and more hair on the upper bract, and in Minnesota, it has a similar range. The larger flowered variety is extant in the Garden. This small flowered variety is not extant.
The flower stems of both can be 8 to 30 inches high and hairy.
Leaves are alternate, ovate and have prominent parallel veins and a base that mostly surrounds (clasps) the stem; leaf margins are smooth but the surface is hairy. Both stem and leaves of the Cypripedium genus can cause dermatitis.
Flowers: Members of the genus Cypripedium have three petals and three sepals that are the same color which can range from yellow-green to purple-brown in this species. Two sepals are joined together as to appear as one lower sepal. This joined sepal and the upper one (of the 3) form a lower and upper hood. Two petals are usually horizontal or descending, usually spirally twisted and usually purple-brown in color. The lower petal forms an inflated lip, or pouch, or slipper, which is yellow, sometimes with purple veining and with some reddish brown dots on the inside. The larger variety (var. pubescens) has flowers from 2 to 3 1/8 inches long and a pouch 1-1/8 to 2 inches long while this smaller variety has a flower that is 1 to 2 inches long with the yellow pouch from 3/4 to 1 1/8 inches long and the sepals and petals are of darker color. The pouches of both varieties may show purple veins. There is usually one but may be two flowers on an inflorescence. Behind the flower stem is a green bract, resembling the leaves but smaller. The bract has a sparse amount of surface hair when young, more appearing later. The sexual parts are inside the pouch, somewhat hidden by a the large ovoid dorsal anther of a false stamen (a staminode). There is a real anther to either side. The flowers have a sweet scent.
Seed: Pollination is usually be bees and fertile flowers produce an ellipsoid capsule containing many small seeds, but reproduction is normally via the root system.
Habitat: Unlike the larger flowered var. pubescens, var. makasin is found in wet to moist conifer swamps, fens, wet meadows and other such areas. It tolerates sun but resists transplanting due to a symbiotic relationship with certain soil fungus called “mycorrhiza.” The root system is rhizomatous and will form a nice clump via enlargement of the root system.
Names: The former scientific name for this species was Cypripedium calceolus (L.) var. parviflorum but that is no longer accepted. The genus Cypripedium is derived from several Greek words that mean "Venus's shoe". The species name, parviflorum, is from the Latin meaning "small flower".
The authors of the accepted plant classification are as follows: For the species itself ‘Salisb.’ refers to Richard Anthony Salisbury, (1761-1829), British botanist who developed an extensive garden and published many taxonomic revisions, but much of his work was plagiarized and discredited, however some of his work has been reinstated as is the case here. As to the variety, the first to publish was ‘Farw.’ who was Oliver Atkins Farwell (1867-1944) American Botanist. His work was amended by ‘Sheviak’ who is Charles J. Sheviak, (b. 1947) American botanist and expert on the Orchidaceae family.
Varieties: There are three varieties of C. parviflorum. The variety "pubescens" (which means 'downy') is used to designate the larger flowered variety with its hairy stems, bract and leaves, compared to variety makasin, (Cypripedium parviflorum Salisb. var. makasin), which has smaller flowers and sparse hair on the bract, and which grows in swamps and bogs and was formerly present in the Garden (see historic photo below). The larger flowered variety can occur more often on upland sites, which is where it is situated in the Garden. The third variety, var. parviflorum is also small flowered, with less hair but has much more densely spotted or blotched sepals and petals and is more restricted in range into areas that are south and east of Minnesota, Iowa and Wisconsin. According to Flora of North America only this variety should be called "Lesser Yellow Lady's-slipper".
Above: Only one or two slippers form on the top of the stem. The green bract behind the flower has sparse hair when young, more dense later. The pouch of the slipper is distinctly smaller than var. pubescens, but with similar coloration. The twisted petals are a much deeper shade of purple than var. pubescens.
Below: For comparison - an example of the two varieties of Greater Yellow Lady's-slipper. 1st photo is of var. pubescens, 2nd photo is of var. makasin. Note the coloration and development, including the hairy stem and the green bract behind the flower are much the same as the larger variety - only the darker color of the purple-brown parts and the size is different.
Below: 1st photo - the hairy angled seed capsule. 2nd photo - Detail of leaf joint with the stem. The leaf is almost fully clasping.
Below: A typical dense clump of variety makasin of Yellow Lady's-slipper. Clumps form by growth of the rhizomatous root system.
Historic Photo - Below: A clump of Yellow Lady's-slipper, var. makasin, in the Woodland Garden on June 6, 1957. Photo from a Kodachrome slide taken by Martha Crone.
Notes: While the larger flowered variety, C. parviflorum var. pubescens, is indigenous to the Garden area of Wirth Park, the smaller flowered variety was introduced to the Garden. Eloise Butler first planted it in 1911 with plants obtained from Gillett's Nursery in North Carolina. She got more in 1915 and more in 1919 from an area around 6th ave. No. in Minneapolis. Martha Crone must have loved the plant as she planted it numerous times beginning in 1933, then in '34, '36, '47, '48, '49, '50, '55, '56, and '57. She generally obtained her plants from wild areas - those in '33 from near Anoka. Cypripediums are difficult to grow via transplanting due to their root system. One must not expect to have a long-lived clump. The species died out sometime and Ken Avery replanted it in 1962 and it again died out. Cary George reported planting several clumps received from Friends Board member Mel Duoos in 1993. It has not been replanted in recent history.
Both varieties are native to Minnesota in the old woods band from Blue Earth County in the SE to Clay County in the NW. In Minnesota the larger flowered variety is more commonly found although the Minnesota Department of Natural Resources lists 59 counties in which the smaller flowered variety has been located. Because of its habitat requirement, the var. makasin has less geographic distribution in North America than its larger flowered cousin. While it is found in most of Canada, it is not found in the U.S. south of of line from Iowa to New Jersey. It has been reported in Colorado and California but not widespread.
For an article on both Lady's-slippers in the Garden and some history see Orchids in the Garden by Cary George in the Archive - Educational section.
There are six Cypripediums found in Minnesota: C. reginae, Showy Lady-s-slipper; C. acaule, Stem-less Lady-slipper (or Moccasin flower); C x andrewsii, Andrews's Lady-slipper; C. arietinum, Ram's head Lady-slipper; C. candidum, White Lady's-slipper; and C. parviflorum, Greater Yellow Lady's-slipper in two varieties - var. makasin and var. pubescens.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"