Botrychium michiganense (Michigan Moonwort)
|Also known as:|
|Habitat:||part shade, sun; average to dry sandy or calcareous soil; open fields, open woods, dunes, roadsides, mine tailings|
|Fruiting season:||June - July|
|Plant height:||2 to 8 inches|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Leaves and stems:
The sterile leaf, called a trophophore, is single near the top of the stem with up to 7 pairs of leaflets (pinnae). The lowest (basal) pinnae are largest, usually dramatically longer than the pair above it, and often deeply divided into rounded lobes. Pinnae above the basal pair become smaller as they ascend the stalk, smooth along the edges or sparingly notched or shallowly toothed, with incisions mostly on the lower edge of the pinnae. Shape is narrowly egg-shaped to lance-elliptic. The trophophore is up to about 2 inches long, to 1 inch at the widest point, held ascending to erect, usually stalkless or nearly so (3mm or less), and is dull gray-green to green in color.
The stem is smooth and commonly red to maroon-tinged especially near the base.
At the top of the stem is the fertile frond, called a sporophore, often twice as long as the trophophore and rising above it at the end of a stalk ½ to 1 times as long as the trophophore. The sporophore is usually divided into 3 main branches, often all near the same length, each branch with a few to numerous smaller side branches. Spores develop all along the branches in small, round capsules (sporangia) that turn yellow when mature in June and July.
Botrychium michiganense is a new species, apparently first identified in Ontario in 1990. Up until then it was likely treated as Botrychium matricariifolium from Minnesota eastward, and as B. hesperium from the Dakotas westward. There are not currently any official records in the Bell Herbarium; it is likely some portion of the B. matricariifolium records will be changed to B. michiganense after review.
While B. matricariifolium is a highly variable species, when its basal pinnae are disproportionately longer than the pair above, it strongly resembles B. michiganense, but its trophophore is usually stalked, and pinnae above the basal pair are often toothed or lobed on both the upper and lower edges where B. michiganense pinnae are mostly cut just on the lower edge (see photo below). Both species have a reddish stem and often grow side by side, along with several other Botrychium species. As with all Botrychium species, examination of several specimens in a population is often needed for a positive ID, and an expert consultation may ultimately be required.
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- Botrychium michiganense plant
- Botrychium michiganense plant
- basal pinnae not dramatically larger than the pair above
- Botrychium matricariifolium trophophore compared to B. michiganense
Photos courtesy Peter M. Dziuk taken in Cook and St. Louis counties.
Have you seen this plant in Minnesota, or have any other comments about it?