Leaves and stems:

Sterile frond is a single leaf, triangular in outline, 4 to 10 inches long and about as wide, 3 or 4 times compound and often appearing as a whorl of 3 leaves, each with up to 12 pairs of leaflets. Leaflets are thin, bright green, linear to narrowly lance-shaped, tapering to a pointed tip, have a prominent midvein, are typically deeply lobed, the lobes shallowly lobed to coarsely toothed and blunt at the tip. Veins are free. Leaves are held horizontal or nearly so. The stem below the leaf (stipe) is 2 to 8 inches long, red-tinged especially near the base. Leaves and stems are hairless.

Spores:

The fertile frond is a branched cluster that arises from the base of the leaf, the central stalk appearing as a continuation of the main stem and is half to twice as long as the sterile frond. Six or more erect to ascending branches are at the tip, with hundreds of pale yellowish-green, bead-like capsules that contain the spores. Spores turn brown when mature.

Notes:

Formerly known as Botrychium virginianum, Rattlesnake Fern is the most common of the grape ferns in North America, and the largest of those found in Minnesota. The finely dissected leaves may resemble those of some other grape ferns (now Sceptridium species), but Rattlesnake Fern is distinguished by the single sterile leaf (often seeming like a whorl of 3 leaves) attached well above the base of the stem, where other grape fern sterile fronds are attached at or near the base. Rattlesnake Fern leaves also wither away by fall where most grape fern leaves persist through winter.