Spiny wood fern fronds arise in clumps, and can reach 1 m tall but are more commonly up to 50 cm tall. The fronds are deciduous, broadly oblong in outline, 3-pinnate and the lowest pair of pinnae are the longest and asymmetrically triangular. The sori are roundish with a persistent, horseshoe-shaped indusium. Spiny wood fern is common and grows in moist woods and openings from low to subalpine elevations.