Malaxis paludosa (L.) Sw.
Bog Adder's Mouth
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Basis for Listing
This diminutive orchid presents an interesting problem in plant distribution. It is generally regarded as frequent in northern Europe, but it is extremely rare in North America. In fact, Malaxis paludosa was unknown on the continent until 1904 when it was collected near New York Mills, Minnesota in Otter Tail County. Since then it has been found at only a few isolated locations in Canada and Alaska in addition to the handful of sites in Minnesota. For this reason, M. paludosa is often considered the rarest orchid in North America. It is not only rare but also easily overlooked. This is because of its small stature (its flowers may be the smallest of any North American orchid), and its habit of growing on moss hummocks where its greenish color makes it difficult to see. Furthermore, the leaves are often concealed beneath the mosses and only the slender inflorescence (sometimes only 2-5 cm tall; 0.8-2 in.) is visible above the moss carpet. Malaxis paludosa was listed as an endangered species in Minnesota in 1984.
Malaxis paludosa has 2-5 alternate, basal leaves that subtend a pseudobulb. Leaves may also develop marginal bulblet-like reproductive structures. The inflorescence is spicate and very slender with up to 30 tiny, yellowish-green flowers with ovate petals. Malaxis paludosa bears a superficial resemblance to the somewhat larger M. monophyllos (white adder's mouth), which differs in having a single leaf, linear petals, and a long-pointed lip (Smith 1993).
Minnesota populations are found in rich conifer swamps of Picea mariana (black spruce) and Larix laricina (tamarack). In its chosen habitat, M. paludosa generally occurs on hummocks of Sphagnum spp. (sphagnum moss). Individuals sometimes appear to be perched on the moss as if they were not actually rooted. Most populations consist of only a very few individual plants (Smith 1993).
Biology / Life History
Malaxis paludosa is a short-lived perennial that reproduces by seed and by an unusual form of vegetative propagation. In some instances, small bulblet-like structures (foliar embryos) develop at the margins of the leaves. When these embryos or the leaf falls, these structures may develop into plantlets and ultimately into new individuals (ramets). This may explain why plants often appear in clumps.
Conservation / Management
Malaxis paludosa is the smallest and most inconspicuous orchid in Minnesota. For this reason it is easily overlooked, even when one is carefully searching on hands and knees (Smith 1993). The principal potential threats to M. paludosa include changes in the hydrological regime of its habitat and damage to the soil and tree cover. Robust beaver populations have caused flooding of many rich conifer swamps. Forest management practices, including road construction, should make special allowances for protecting this species and its habitat. Because M. paludosa roots in the moss, special care must be taken to preserve the health and integrity of the moss community supporting this rare orchid. The moss layer can be especially sensitive to damage by machinery or heavy equipment, even in winter.
Best Time to Search
The best time to search for this species is from mid-July to late August, when M. paludosa is in flower and fruit.
Conservation Efforts in Minnesota
Since 2005, 16 new locations of M. paludosa have been discovered in the state. All but one of these new locations were found as a result of the Minnesota Biological Survey that has been ongoing in west-central Minnesota since that time. The population discovered in Cass County in 2008 extended the known range of this species in Minnesota approximately 48 km (30 mi.) to the east. Three of the 21 known M. paludosa populations occur in State Parks or natural areas where the habitat is afforded a fairly high degree of protection. However, at one of the three sites, a proposed road construction project may impact the hydrology of the site.
Luer, C. A. 1975. The native orchids of the United States and Canada. New York Botanical Garden, Bronx, New York. 361 pp.
NatureServe. 2008. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.0. NatureServe, Arlington, Virginia.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 320 pp.
Reeves, T., and L. Reeves. 1984. Life history and reproduction of Malaxis paludosa in Minnesota. American Orchid Society Bulletin 53(12):1280-1291.
Smith, W. R. 1993. Orchids of Minnesota. University of Minnesota Press, Minneapolis, Minnesota. 172 pp.