There is an
easy character that helps identify D. intermedia , though it is a little difficult to explain verbally.
We are looking at the proximal (lower) part of the frond (leaf),
particularly at the very lowest segments (pinnae). In Dryopteris pinnae are further divided into smaller segments,
which are called pinnules. Pinnules are tiny near the tip
of the pinna, growing larger toward the rachis (main axis of the
frond). However, the two pinnules closest to the rachis are "out of
order": the last pinnule is not the largest, the one next to it is larger.