Leaves and stems:

The leafy frond, called a trophophore, is single near the top of the stem, oblong in outline, with 3 to 7 pairs of leaflets (pinnae), usually fewer than 5, the largest in the middle of the blade or the lowest pair, depending on the var. The trophophore is 1.5 to 7 cm (to ~2¾ inches) long, held erect to ascending, usually stalkless or nearly so, though the stalk may be as long as 1 cm (3/8 inch) on one var. The stem below the tropophore is 2 to 4 cm (to ~1½ inches) long.

Pinnae are wedge or spatula-shaped and ascending, straight or concave on the sides, span an angle 45 degrees or less, and tend to fold in towards the stalk. The tip edge varies from smooth to irregularly toothed, notched or lobed, the lobes wedge-shaped to linear.

Spores:

At the top of the stem is the fertile frond, called a sporophore, 1 to 8 cm (to ~3 inches) long, usually about as long as the trophophore and barely rising above it. The stalk is less than half as long as the tropophore, usually ¼ or less. The sporophore typically has numerous short branches, each with several round capsules of spores (sporangia) that mature in June then turn brown when spores are released by mid-July.

Notes:

Prairie Moonwort is one of the few Botrychium species considered prairie specialists, where most are considered forest species. In Minnesota, it is found in dry, sandy or rocky soil, or in glacial till (a sediment deposit of mixed sand, gravel and clay with no stratification). Habitats include hill and bluff prairies as well as gravel pits, mine dumps and tailings basins. There are two vars, both of which are present in Minnesota: var. campestre and var. lineare, which may grow together, and both of which consistently have short-stalked to stalkless tropophores and a sporophore stalk about ¼ or less as long as the tropophore, which helps distinguish them from several other Botrychiums. Both emerge in spring, develop spores in June, and wither away in July after spore release.

The more common, var. campestre, is the smaller of the two, characterized by a tropophore 1.5 to 5 cm (½ to 2 inches) long on a stalk 0 to 2 mm long, the largest pinnae usually in the middle of the leaf, pinnae tips sometimes smooth but more typically irregularly toothed or lobed and the lobes mostly wedge-shaped. And it is tiny; a 1-inch tall mature specimen is not unheard of. According to the DNR, this was the first Botrychium known as a prairie species and sparked an interest in further exploration for other previously undescribed Botrychiums. While there are 100+ records of this to-date, its actual rarity in the state is unknown, likely due to its tiny size and the short window of opportunity to find it. It was listed as a Special Concern species in 1996.

The more rare var. lineare was originally considered a separate species (B. lineare), but genetic testing concluded it was more appropriately a var of B. campestre. It tends to be a somewhat larger plant, the tropophore reaching up to 7 cm (2¾ inches) long, the lowest pinnae pair typically largest and its stalk up to 1 cm (3/8 inch) long. The more obvious distinction is the pinnae, which are divided into linear, finger-like lobes that tend to diverge at a 45 degree angle, and are the narrowest lobes of any Botrychium. According to the DNR, the first MN record was in Crow Wing County in 2000, and has since only been found in a handful of locations, all with small populations. It was listed as Endangered in 2013.

The shape of the pinnae may be similar to other Botrychiums as well, but these can all be variable on individuals so it's helpful to examine multiple plants within a population (if you can find any). Having said that, Botrychium identification is difficult even for the experts so don't be discouraged if you struggle to get it down to species.