Leaves and stems:

The leafy frond, called a trophophore, is single near the top of the stem, oblong in outline, with 3 to 10 pairs of leaflets (pinnae) more or less evenly distributed along the stalk, often well separated from each other. Pinnae may or may not fold in towards the stalk. The trophophore is 2.5 to 11 cm (1 to 4+ inches) long, held erect, the stalk 3 to 15 mm (to ~½ inch) long. The stem below the tropophore is 2.5 to 6 cm (to 2+ inches) long.

Pinnae are mostly ascending, spoon to fan-shaped, the sides straight or concave, the curvature usually strongest at the base, and span an angle of 60 to 120 degrees. The tip edge is smooth or scalloped, sometimes notched to about a third its length. Pinnae tend to be similar in size and shape except for the uppermost and perhaps the lowest pair. Robust plants may be more blunt-toothed along the tip edge and/or have pinnae more crowded on the stalk.

Spores:

At the top of the stem is the fertile frond, called a sporophore, 3 to 10 cm (to 4 inches) long, rising above the tropophore at the end of a stalk 2 to 5 cm (to 2 inches) long. The sporophore typically has numerous short branches, each with a few to several round capsules of spores (sporangia) that mature starting in June then turn brown when spores are released starting in July.

Notes:

Mingan Moonwort is one of the more common Botrychium species in North America, found in the northern latitudes from coast to coast and higher altitudes in the western US. According to the DNR, the first Minnesota record is from 1894 in Lake of the Woods County. Habitats are primarily deciduous and mixed forests, but also in grassy roadside openings, cliffs, mine tailings basins, and old fields and homesteads, often in deep thatch. It is usually found as scattered individuals, often mixed with other Botrychium species. It was listed as Special Concern in 1996.

Its typical form has a stalked tropophore with up to 10 pairs of pinnae that are often widely spaced, span an angle of 60 to 120 degrees, are spoon to fan-shaped, straight or concave on the sides, and tips are smooth, scalloped or shallowly notched. Most pinnae are a similar size and shape, though the lowest pair may be a bit larger and the uppermost pairs a bit smaller. A robust plant may have more crowded pinnae with blunt-toothed tips.

Most similar is B. neolunaria (New World Moonwort), which has fewer pinnae that are typically wider, the lowest pair spanning an angle of up to 180 degrees, and the tropophore is stalkless or nearly so. Somewhat similar is B. pallidum (Pale Moonwort), which has a porportionately shorter tropophore with fewer pinnae, and live plants tend to be pale green, blue-green or gray-green. B. spathulatum (Spatulate [or Scalloped] Moonwort) may have similarly shaped and widely spaced pinnae, but the tropophore is stalkless and lowest pinnae pair often clasp the sporophore stalk.

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 them). 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.