Polypodium virginianum aka Rock Polypody

Polypodium virginianum is a small fern that stays green year-round. It belongs to the Polypodiaceae family. People call it rock polypody or American wall fern. Its native range spans subarctic North America. It also spans the eastern and central United States. In the north, it reaches Greenland and Alaska. This fern is a fertile hybrid that arose in nature. Its two parent species are Polypodium appalachianum and Polypodium sibiricum. It looks much like the first parent. This can make it hard to tell them apart.

Plants grow about 0.5–1 foot (0.15–0.3 metres) tall and wide. Their rhizomes creep and branch, forming clumps. These clumps can spread to form colonies. The fronds stand upright or arch out from the clump. Their blades feel like leather. They range from a lance shape to a triangle. Deep cuts split each blade into oblong lobes. The lobes grow shorter near the base and tip. Each blade is widest near its middle. Scales cover the lower parts of the leaf stalks. The stalks are smooth higher up. They measure one-quarter to one-half of the blade length.

This fern has no flowers or fruit; it makes spores. Large, round patches called sori hold spores on the fronds. These patches range from orange to brown. They form rows beside the central vein. They have no indusium, the cover that protects sori. Long brown hairs grow among the sori. Fronds with and without spores look much alike. Nectaries sit at the base of each frond blade. The leaves stay green and give the plant winter value.

In the wild, it grows over rocks and moss-covered tree roots. It also grows on ledges and rock walls. It lives in narrow cracks in bluffs, too. In gardens, it suits part shade through deep shade. It prefers moist soil rich in humus, with good drainage. Acid to neutral soils suit it, including loam and sand. It also grows in shallow, rocky ground. Once plants take hold, they cope with drought and dry spells. They need moderate water and grow at a medium rate. Sources place their hardiness in USDA zones 3–8.

Use this fern in rock gardens, native beds or shaded woods. Groups can edge paths or fill gaps among rocks. Plants may take time to settle in. Once settled, they need little care. You can divide plants to make more. Deer and rabbits tend to leave this fern alone. Sources report few major problems with pests or disease. Watch for one pest, the Florida fern caterpillar. Native Americans used it for ailments of the gut and upper airways. The supplied sources do not show whether it is edible or toxic.