The fronds of Thelypteris palustris are spread out along
a rhizome, and are therefore not conspicuously clumped. The blades
are pinnate-pinnatifid, slightly tapered to the base and 10-40
cm long. Sori are round with true indusia (though little or no
evidence of the indusia remain after the fertile fronds have reached
maturity). Fertile leaves tend to be a little narrower and the
pinnae often appear a little smaller, in part because the margins
of the segments are slightly curled toward the abaxial surface.
The sori are often numerous and very close together, essentially
covering most of the undersurface of fertile pinnae.
Veins in the blade segments are branched, in contrast to the
similar T. simulata for which the veins are unbranched.
Two varieties of T. palustris have been recognized, but
only variety pubescens is found in North America. T.
palustris variety pubescens ranges from Newfoundland
to Florida, west to Texas, South Dakota and Manitoba. It is common
throughout Wisconsin on wet soils in both sunny and shaded sites,
including bogs, sedge meadows and swamps.