Thelypteris palustris (Northern Marsh Fern)

Plant Info
Also known as: Eastern Marsh Fern
Genus:Thelypteris
Family:Thelypteridaceae (Marsh Fern)
Life cycle:perennial
Origin:native
Habitat:part shade, sun; bogs, marshes, wet meadows, seeps, fens, along shores
Fruiting season:summer
Plant height:6 to 30 inches
Wetland Indicator Status:GP: OBL MW: OBL NCNE: FACW
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Leaves and stems: Leaf attachment: basal Leaf type: compound

[photo of leaves] Leaves are once compound, 6 to 30 inches long and 3 to 7 inches wide, lanceolate shaped in outline, the lowest leaflets at least half as long as the longest ones below the middle of the leaf. Leaf surfaces are typically hairless though the leaflet mid-nerve is slightly hairy. Leaves are mostly erect, growing in a random pattern from creeping rhizomes.

[photo of veins on a sterile leaf] Leaflets are light green, deeply lobed, divided almost to mid-nerve, the lobes up to ¾-inch long, oblong to triangular, toothless with a blunt to pointed tip. Veins extend to the edge of the lobe and are mostly forked, though fertile leaves have some unforked veins.

[photo of lower stem] The base of the stem is smooth and dark brown to black with a few scattered small tan scales. The upper stem is slightly hairy and green to straw-colored, sometimes with a few scattered scales.

Spores: Fruit type: spores on leaf

[photo of spores] Spores mature in mid to late summer, appearing on the back of fertile leaves, which are more erect, taller and narrower than the infertile leaves. The sori (group of spores) are round and covered by tissue (indusium). The sori are in a row on both sides of the lobe midvein, the sori attached on the veins. The leaf edges slightly roll under, slightly covering the sori.

Notes:

This is a common fern of wet sunny places, though it does tolerate light shade and is not typically found in standing water. A non-clumping fern, it often forms colonies from its long creeping rhizomes. Flora of North America notes 2 varieties in North America; var. pubescens is found in Minnesota as well as about 2/3 of the rest of North America. Northern Marsh Fern may look similar to Lady Fern (Athyrium Filix-femina) but Lady Fern grows in clumps and has distinctly toothed leaflets.

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More photos

Photos by K. Chayka taken at Cedar Creek Natural History Center, Battle Creek Regional Park, and Blaine Preserve SNA. Photos courtesy Peter M. Dziuk taken in Anoka County.

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