Polystichum braunii (Braun's Holly Fern)
|Also known as:||Prickly Shield Fern|
|Family:||Dryopteridaceae (Wood Fern)|
|Habitat:||part shade, shade; cool, moist, boreal forest, ravines, rocky slopes, cliff bases|
|Fruiting season:||mid to late summer|
|Plant height:||12 to 40 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:
Leaves (fronds) are evergreen, up to 40 inches long and 8 inches wide, twice compound, lance-elliptic in outline, widest at about the middle, tapering to a pointed tip and gradually tapering at the base, with branches (pinnae) all along the stem nearly all the way to the ground, the lowest pinnae very short. Pinnae are up to 4 inches long, mostly lance-oblong in outline with 9 to 15 pairs of leaflets (pinnules).
Pinnules are sharply toothed, the teeth with bristled tips and curved up towards the pinnule tip (falcate). The upper surface is dark, glossy green, the lower surface paler. Stems (rachis) are densely covered in tan scales, especially near the base.
The sori (group of spores) are found on the underside of the pinnule. They are circular and arranged in 2 rows, 1 on each side of the pinnule mid-vein. A translucent tissue (indusium) partly covers the spores and is attached to a stalk on the underside; it shrivels up as spores mature. Spores ripen to gray-brown or black starting in mid-summer. Not all fronds have spores and there is no other visible difference between fertile and sterile fronds.
Braun's Holly Fern is a species of cool, boreal forest and is only known from a handful of locations in Cook and Lake Counties. According to the DNR, it was first discovered in Minnesota in 1966 and listed as Endangered in 1984, but was downgraded to Threatened in 2013 after biological surveys discovered additional populations. It is somewhat more widespread in Wisconsin and also listed there as a Threatened species. It is distinguished from other ferns of similar size, such as Lady Fern (Athyrium Filix-femina) and the related Christmas Fern (Polystichum acrostichoides), by the following combination of characteristics: rachis (stems) covered in tan scales, many auricled pinnules (leaflets), and the pinnae (branches) gradually tapering in size nearly all the way to the ground, with the lowest pinnae very short.
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Photos courtesy Peter M. Dziuk taken in Cook County.
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