Shield fern (dryopteris expansa, also known as the spiny wood fern), is a deciduous fern that prefers most forests in the Pacific Northwest. The fronds are erect, clustered but spreading, and can reach up to one meter tall. It has asymmetrical pinnae at the pair closest to the base, and female ferns are three times pinnate while males are two times. The frond is shaped like a triangle, with and oblong shape in the middle and a fast taper at the end. It can have five to twenty pairs of leaflets, each with their own pairs of about 10 leaflets. Sori are rounded and partially covered.
- Deciduous, erect and clustered, can reach one meter tall
- Females are three-times pinnate, while males are two times
- Asymmetrical pinnae at pair closest to base
- Frond shaped like a triangle, with five to twenty pairs of leaflets