Western Moonwort - Botrychium hesperium
Botrychium matricariifolium, Botrychium michiganense [in part]
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This moonwort species is known from 25-30 extant sites in western Montana, mostly in Glacier National Park or on National Forest lands. Many sites are poorly documented in terms of population size or are small in size, though several sites have been observed with >100 plants. Many populations occur on roadsides or other similarly open or disturbed habitats. As such, the species is vulnerable to activities such as weed invasion, weed spraying and road maintenance.
Western Moonwort is a small perennial fern with a single erect frond, 3-13 cm high. It is divided into a sterile segment and a fertile segment. The sterile segment has a stalk 0-4 mm long, and a broadly lance-shaped to triangular blade that is pinnately divided with 1-6 pairs of closely adjacent leaflets (pinnae). The basal pinnae are usually partly to wholly pinnately divided and are larger than the lobed or entire-margined upper pinnae. The fertile segment is 2-3 times as long as the sterile segment and 1-3 times pinnately divided into linear segments that bear the spores.
Leaves appearing in mid-spring, dying in early fall. Mature fronds in June-July.
The subgenus Botrychium is a large group of very similar species, many of which have been recently described. A technical manual should be consulted for positive identification. The deeply pinnately lobed basal pinnae help separate this species from most others in our area.
In MT according to Lesica (2012) in Lincoln, Flathead and Glacier counties, but Farrar (unpublished) indicates a broader distribution across MT ; AK, BC and AB south to WA, ID, WY, UT, AZ and CO (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX; Donald Farrar (unpublished ms., Iowa State University). ).
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Various dry to mesic sites from valley bottoms to the subalpine, including roadsides and other disturbed habitats. Common moonwort associates include B. paradoxum, B. lunaria and B. lanceolatum. Other moonworts reported at B. hesperium sites include B. minganense, B. adnatum, B. pedunculosum, B. ascendens, B. lineare, B. gallicomontanum, B. pinnatum, B. crenulatum, B. simplex and B. pallidum.
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- Ahlenslager, K. and P. Lesica. 1995. Observations of Botrychium watertonense and its putative parent species, B. herperium and B. paradoxum. Draft manuscript prepared in cooperation with Waterton Lakes National Park, USFWS, and Montana Natural Heritage Program. 13 pp.
- Ahlenslager, K. and P. Lesica. 1996. Observations of Botrychium x watertonense and its putative parent species, B. hesperium and B. paradoxum. American Fern Journal 86(1):1-7.
- Farrar, Donald. 2011. Moonwort (Botrychium) Systematics. Ada Hayden Herbarium. Iowa State University.
- Lesica, P. and K. Ahlenslager. 1994. Demographic monitoring of three species of Botrychium (Ophioglossaceae) in Waterton Lakes Park, Alberta: 1993 progress report. Unpublished report to the U.S. Fish and Wildlife Service. Montana Natural Heritage Program, Helena, Montana. 19 pp.
- Lesica, P. and K. Ahlenslager. 1995. Demography and life history of three sympatric species of Botrychium subg. Botrychium in Waterton Lakes National Park, Alberta, Canada. Draft manuscript prepared in cooperation with Waterton National Park, U.S. Fish and Wildlife Service, and Montana Natural Heritage Program. 22 pp.
- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Mantas, M. and R.S. Wirt. 1995. Moonworts of western Montana (Botrychium subgenus Botrychium). Flathead National Forest. 103 pp.
- Wagner, Jr., W.H., F.S. Wagner, C. Haufler and J.K. Emerson. 1984. A new nothospecies of moonwort (Ophioglossaceae, Botrychium). Canadian Journal of Botany 62:629-634.
- Wagner, W. and F. Wagner. 1986. Three New Species of Moonworts (Botrychium Subgenus Botrychium) Endemic in Western North America. American Fern Journal 76 (2):3347
- Wagner, W. H. and F. S. Wagner. 1993. Ophioglossaceae. In: Flora of North America Editorial Committee, eds. 1993. Flora of North America North of Mexico. 3+ vols. New York and Oxford. Vol. 2, pp. 85-106.
- Wagner, W.H., and F.S Wagner. 1981. New Species of Moonworts, Botrychium Subgenus. Botrychium, From American Fern Journal 71:20-30.