Leaves and stems:

At the top of the stem is a single compound leaf (frond), triangular in outline, 6 to 16 inches long, usually about as wide as long, with 12 to 15 pairs of branches (pinnae) oppositely arranged. The central frond stem (rachis) is winged with leaf-like appendages that connect all of the pinnae together, including the lowest pair. Pinnae are mostly oblong in outline, tapering to a pointed tip with the lowest pair largest and more lance-elliptic, narrowed at the base, and spreading or angled down where the rest are spreading. The fronds are held at an angle, often parallel with the ground, so plant height is typically under 20 inches though may be 30 inches when the frond is fully extended upright.

Pinnae are divided into 10 to 20 pair of lobes that are oblong in outline, rounded at the tip, smooth to somewhat scalloped along the edge. Veins are branched or simple (unbranched) but often forked especially on the larger pinnae. Edges are sparsely hairy, the upper surface hairless, the lower surface mostly hairless but may have scattered yellowish glands on the surface and/or veins. Pinnae stalks (costae) are hairy and may or may not have a few scattered scales. The frond stalk (rachis) is also hairy on the underside with few light brown scales.

The main stem (stipe) is typically purplish-brown or straw-colored at the base, becoming straw-colored to green above. The base is hairless with sparse scales, the stipe becoming hairy at the base of the frond. Plants may form loose clumps and can create loose colonies from long, creeping rhizomes.

Spores:

The sori (group of spores) are found on the underside of the leaf. They are circular and arranged near the edges of a pinnae lobe, near the tip of a vein. There may be a few yellowish, short-stalked glands along the keel of an individual spore case. There is no extra tissue (indusium) that surrounds or covers the spores. Spores ripen to dark brown. Not all leaves have spores and there is no visible difference between fertile and sterile fronds, though the earliest leaves are sterile, the fertile leaves emerging later.

Notes:

Broad Beech Fern is quite rare in Minnesota, where it reaches the western edge of its range in the southeast corner of the state, first recorded in 1903 in Houston County and not again for another 55 years. According to the DNR, when it was first listed as a Special Concern species in 1984, there were only 5 records in the state. Subsequent biological surveys only found one additional population and it was elevated to Threatened in 1996, then to Endangered in 2013 when only one of the historical populations were relocated; it is currently Special Concern in Wisconsin. We did repeated searches for it at its most recently recorded Minnesota location in Fillmore County but failed to locate it there ourselves. Likewise, surveys in Wisconsin came up empty but we finally had success in the Upper Peninsula of Michigan where it is more abundant (thanks to Joe Waleski for the waypoint).

It is fairly easy to ID from the winged stem that connects all the pinnae together, including the lowest pair, and fronds usually about as wide as long. It is very similar to the related Long Beech Fern (Phegopteris connectilis), which is much more common especially in the northeast quadrant of Minnesota, and has fronds usually longer than wide with a distinct gap in the wing along the rachis above the lowest pair.

A few more subtle differences exist between the two, which may or may not be reliable in the field. P. connectilis pinnae veins are mostly simple (unbranched) where P. hexagonoptera veins are more often forked or branched, at least on the larger pinnae. The rachis (central frond stalk) of P. connectilis is hairy and more moderately covered in brown scales, where the P. hexagonoptera rachis is hairy but may have only a few pale scales. The lowest P. connectilis pinnae strongly point downward, where those of P. hexagonoptera are spreading or descending but not usually as reflexed. Several references note that P. connectilis scale color on the pinnae is tan or brown where P. hexagonoptera is whitish or tan, but we found white scales on numerous P. connectilis specimens that appeared to shrivel up and turn dark brown over time; P. connectilis does have far more scales on the rachis and costae, though. The yellowish, stalked glands are also noted only for P. hexagonoptera, though we found some present on P. connectilis as well (magnification required). The two have been known to hybridize but no hybrids have been recorded in Minnesota.

Note that the gap on P. connectilis is sometimes very short so location within MN may help with an ID, as will the combination of some of the more subtle characteristics. Case in point: a population we checked in Wisconsin, previously identified as P. hexagonoptera, did have what appeared to be a continuous wing even between the lowest pair of pinnae. However we found no forked veins anywhere, there were abundant brown scales on the rachis, and the lowest pinnae were quite strongly reflexed. After some consideration, we determined it was more likely P. connectilis.