Leaves and stems:

The leafy frond, called a trophophore, is single near the top of the stem, oblong in outline, with 3 to 6 pairs of leaflets (pinnae) more or less evenly distributed along the stalk with the lowest pair typically largest. Pinnae may or may not fold in towards the stalk. Color is pale green, gray-green or blue-green, which is only seen on living plants. The trophophore is 1.2 to 4 cm (to ~1½ inches) long, held erect, the stalk 2 to 15 mm (~½ inch) long. The stem below the tropophore is 1.5 to 7 cm (to 2¾ inches) long. Plants often grow in clumps.

Pinnae are ascending to spreading, broadly spoon to fan or mushroom-shaped, the sides straight or concave, and spanning an angle of 60 to 120 degrees. The tip edge is smooth, scalloped or blunt-toothed, the largest pinnae often asymmetrically lobed; when lobed, the upper lobe is usually largest.

Spores:

At the top of the stem is the fertile frond, called a sporophore, 3 to 8 cm (to ~3 inches) long, usually noticeably larger than the trophophore and rising above it at the end of a stalk half to 1½ times as long as the trophophore. The sporophore typically has numerous short branches, each with several to numerous round capsules of spores (sporangia) that mature starting in June then turn brown when spores are released in July. It is not unusual for the tropophore to also have a few sporangia on the lowest pair of pinnae.

Notes:

Pale Moonwort was first described as a species in 1990 and the first Minnesota population found in northern St. Louis County in 1992. According to the DNR, at the time it was considered quite rare in North America, only known from a few states and provinces along the Canadian border, and was listed as Endangered in 1996. Subsequent surveys found it to be much more common than previously known and it was downgraded to Special Concern in 2013. It can be found in a wide range of habitats, in forests and clearings, grassy roadside openings, cliffs, mine dumps and tailings basins, and old fields and homesteads.

It is most easily recognized by the pale color that may be gray-green or blue-green, but this is only seen on live plants and is not always pronounced. The tropophore is stalked and tends to be small with 3 to 6 pairs of pinnae, which span an angle of 60 to 120 degrees, are straight or concave on the sides, and smooth, scalloped or blunt-toothed along the top edge. Larger pinnae may be asymmetrically lobed, the top lobe typically largest. It is not unusual to see a few sporangia on the lowest pair of pinnae.

Most similar is B. minganense (Mingan Moonwort), which is yellow-green and has a larger tropophore with up to 10 pairs of pinnae. The curvature of its pinnae sides tends to be strongest at the base, straightening towards the tip, where the B. pallidum curvature tends to be more uniform from base to tip, or stronger towards the tip.

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.