PROTECTING WISCONSIN'S BIODIVERSITY

 
 
   
 
Scientific Name Common Name Global Rank State Rank Federal Status WI Status

Spreading Woodfern (Dryopteris expansa)

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Photo by R.C. Moran

 

Counties with Mapped NHI Occurrences

Spreading Woodfern (Dryopteris expansa), a Wisconsin Special Concern plant, is found in cool coniferous (balsam-fir, white cedar, hemlock) to mixed forests, sometimes in cold canyons. The optimal identification period for this species is late-May through September.

Dryopteris assimilis, Dryopteris dilatata, Dryopteris dilatata ssp. americana, Dryopteris spinulosa var. americana

 
 
 

Spreading woodfern has fronds that are up to 1m tall. It has lanceolate to ovate-lanceolate leaves, 20-60cm long, 15-30cm wide, and broadest above the base, acute-acuminate at the base and apex, 3-pinnate-pinnatifid at the base, and 2-pinnate-pinnatifid above the base. Pinnae and the pinnules are nearly equilateral, except for the basal pinnae, which are expanded. Basal basiscopic pinnules (downward pointing, or lower portion of basal pinnules) are 2-3 times longer than the basal acroscopic ones (upward pointing, or upper portion of the basal pinnules). The pinnule segments and lobes are spinulose, the laminae eglandular or slightly glandular. Sori are round, protected by a reniform indusium, and appear in a single series on each side of segment midrib. Stipes are 10-40cm long, with pale brown scales usually having a darker brown, broad, central strip or basal area. Indusia are medial or submedial, eglandular.

Rhizomatous. Fruiting occurs in late-summer.

Perennial. The optimal identification period for this species is late-May through September.

Associated species include Abies balsamea, Thuja occidentalis, Tsuga canadensis, Acer rubrum, A saccharum, A spicatum, Betula alleghaniensis, Polystichum braunii, Dryopteris cathusiana, and D intermedia.

Spreading woodfern prefers moist, often rocky soils and is found in cool coniferous (balsam-fir, white cedar, hemlock) to mixed forests, sometimes in cold canyons.

Avoid broadcast spraying of herbicides and use care with spot spraying.

Avoid direct disturbance to sensitive microsites such as seeps, cliffs, and moss-covered boulders.

This species overwinters above ground, meaning that seasonal restrictions like conducting the a project on frozen ground will not result in avoidance. Therefore, known individual plant locations should be avoided year-round. Consult with a biologist, if needed.

Avoid (moist or dry) cliffs, rocky areas, slopes, outcrops, ridges, or ledges within forests.

Maintain structural characteristics of old growth forests such as downed logs and other coarse woody debris.

Although maintaining high overall forest canopy is important, silvicultural techniques that open small gaps in the canopy may be beneficial to this species. Seedlings and saplings of some species in openings may need to be protected from deer browse.

Species of Greatest Conservation Need (SGCN) are associated with habitats (or natural communities) and places on the landscape. Understanding relationships among SGCN, natural communities and ecological landscapes help us make decisions about issues affecting SGCN and their habitat and how to respond. Download the Wildlife Action Plan association score spreadsheet to explore rare species, natural communities and ecological landscape associations

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the Wisconsin Wildlife Action Plan because lack of information can threaten our ability to successfully preserve and care for natural resources.