Rare Species Guide

  Synonyms

Hammarbya paludosa

  Basis for Listing

This diminutive orchid presents an interesting problem in plant distribution. It is generally regarded as frequent in parts of northern Europe, but it is extremely rare in North America. In fact, Malaxis paludosa (bog adder’s mouth) was unknown on the continent until it was discovered in Alaska in 1895, then at a few widely scattered sites in Canada. It was unknown in Minnesota until 1904 when it was found near New York Mills 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 that have since been discovered in Minnesota.

Known populations in Minnesota are not only few in number and widely scattered, they are also small, usually with fewer than 20 individuals, and restricted to an ecologically sensitive habitat. Malaxis paludosa was listed as an endangered species in Minnesota in 1984.

  Description

Malaxis paludosa is not only rare but also easily overlooked (Finding the invisible orchid). This is because of its small size (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.

Malaxis paludosa is a small slender plant 6–23 cm (2-9 in.) tall.  There are 2–4 elliptical leaves at the base of the stem, each 1–3 cm (0.4-1.2 in.) long and up to 1 cm (0.4 in.) wide. The stem arises from a small globular pseudobulb that is 4–7 mm (0.2-0.3 in.) long, with roots reduced to short hairs. Its flowers are tiny, upright (not rotated 180 degrees like most orchids), and yellowish-green; there may be as many as 30 on each plant. There are 3 sepals, each 2–3 mm (0.08-0.12 in.) long, and 3 petals. The 2 lateral petals are only 1–1.5 mm (0.04-0.06 in.) long. The third petal is uppermost in the flower and is called the lip. It is up to 2 mm (0.08 in.) long and often constricted, resulting in a vaguely three-lobed shape. The flowers are scattered on a terminal spike-like raceme, each subtended by a 2–3 mm (0.08-0.12 in.) long bract. The fruit is a capsule 3–4 mm (0.12-0.16 in.) long. Flowers are normally present between mid-July and late August (Smith 2012).

  Habitat

What is clear is that M. paludosa has very particular habitat requirements in Minnesota. Large areas in north central Minnesota appear to contain suitable habitat, but field surveys have only rarely turned up new populations. This could be due in part to the paludified landscape typical of the Glacial Lake Agassiz region (Northern Minnesota and Ontario Peatlands Section) that is largely dominated by extensive nutrient-poor swamps. By contrast, all known locations of M. paludosa in west-central Minnesota (Northern Minnesota Drift and Lake Plains Section) are in rich conifer swamps. Its typical habitat is dominated by Picea mariana (black spruce) with occasional Thuja occidentalis (northern white cedar), Larix laricina (tamarack), or Abies balsamea (balsam fir) (Whitfeld et al. 2015).

In Minnesota, the shrub layer of M. paludosa habitat is typically open, with minor amounts of Rhamnus alnifolia (alderleaf buckthorn), Cornus sericea (red-osier dogwood), Rhododendron groenlandicum (Labrador tea), Alnus incana (speckled alder), or Betula pumila (bog birch).

Malaxis paludosa is usually found perched on, or overtopped by, low hummocks of sphagnum moss (Sphagnum spp.) and feathermosses, such as Pleurozium schreberi and Thuidium delicatulum. This growth habit led to the designation by some authors of M. paludosa as the only ‘‘epiphytic orchid’’ in Europe and northern North America (Luer 1975). In several cases, M. paludosa has been found with M. unifolia (green adder’s mouth) and M. monophyllos var. brachypoda (white adder’s mouth), as noted by Reeves and Reeves (1984). By nearly every standard, viable populations of M. paludosa are inseparable from the natural community in which they occur, perhaps even more so than most specialized species.

  Biology / Life History

Malaxis paludosa is a short-lived perennial that reproduces by seed and by a form of vegetative propagation that is unique within the orchid family. It has the ability to produce small apical foliar embryo-like structures at the tips of some leaves. These structures arise directly from leaf tissue and, after dropping from the leaf, develop into plantlets and ultimately into new reproductive individuals. These embryo-like structures develop in the same way as seedlings derived from sexual reproduction, but they do it asexually without the benefits (and costs) of sexual reproduction (Smith 2012; Taylor 1967). This method of vegetative reproduction is not uncommon in other plant families (e.g., Crassulaceae) but is unique among orchids. Whether it is the dominant form of reproduction in M. paludosa is unclear. Seeds are produced by cross-pollination mediated by very small flying insects, such as fungus gnats (Reeves and Reeves 1984), and dispersed short distances by wind. It is also known that M. paludosa is completely dependent on a close (perhaps symbiotic) relationship with mycorrhizal fungi, which are themselves dependent on a healthy tree community.

  Conservation / Management

Malaxis paludosa is the smallest and least conspicuous of Minnesota’s 48 species of native orchids. That is why it is easily overlooked, even when one is carefully searching on hands and knees (Smith 2012). For this reason, a one-time, casual meandering search of suitable habitat cannot conclusively determine the presence or absence of this species. A credible search must be careful, methodical, and performed by someone already familiar with the plant.

The principal threats to M. paludosa include changes in the hydrological regime of its habitat. Robust beaver populations can divert surface waters from streams causing destructive flooding. However, changes in subsurface water is of equal, if not greater, concern. Since M. paludosa habitat is typically sustained by subsurface movement of water, damage can be caused by road building, pipeline installation, and ditching even if those activities are some distance from the population. Damage to the sensitive moss community and compaction of the peat soil can occur even if activities are carried out in winter and should be strictly avoided.

Any management activity that would result in significant alteration of the tree canopy could have unintended and deleterious consequences to a population of M. paludosa. This would likely happen when the amount of light reaching the herbaceous layer of the forest community was suddenly increased, likely favoring the increased growth of woody shrubs. The known occurrences of M. paludosa in Minnesota seem to be negatively correlated to increased shrub cover, though the causal relationship is not known.

  Best Time to Search

The best time to search for this species is from mid-July to late August, when Malaxis 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, which 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.

  Authors/Revisions

Welby R. Smith (MNDNR), 2020

(Note: all content ©MNDNR)

  References and Additional Information

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. . Accessed 9 June 2008.

NatureServe. 2020. NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. <https://explorer.natureserve.org/Search>. Accessed 21 April 2020.

Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis. 320 pp.

Reeves, L. M., and T. Reeves. 1984. Life history and reproduction of Malaxis paludosa in Minnesota. American Orchid Society Bulletin 53(12):1280-1291.

Smith, W. R. 2012. Native orchids of Minnesota. University of Minnesota Press, Minneapolis, Minnesota. 400 pp.

Taylor, R. L. 1967. The foliar embryos of Malaxis paludosa. Canadian Journal of Botany 45(9):1553?1556.

Whitfeld, T. J. S, E. R. Rowe, M. D. Lee, and W. R. Smith. 2015. New occurrences of the elusive Malaxis paludosa (Orchidaceae) in Minnesota. Rhodora 117:98-105.