Polypodium vulgare aka Common Polypody

Polypodium vulgare, or common polypody, is an evergreen fern. It belongs to the polypody family, Polypodiaceae. Its native range spans temperate Eurasia, Madeira, Morocco and southern Africa. It also includes the Kerguelen Islands and Britain and Ireland. This fern grows on the ground or on trees. Wild plants also grow on rocks and old walls. They occupy cracks, tree bases and limbs in shaded sites.

Creeping rhizomes spread sideways and form a low mat. Plants often stand about 1 foot [0.3 metres] tall. The RHS gives a garden height range of 0.3–1.6 feet [0.1–0.5 metres]. Its spread reaches 1.6–3.3 feet [0.5–1 metre]. Plants take five to ten years to reach full size. Growth proceeds at a moderate rate. The green fronds feel leathery and lack hairs. Their shape ranges from lance-shaped to oblong or triangular. Each frond has deep divisions or separate leaflets. These grow smaller toward the tip, with smooth or toothed edges.

This fern has no flowers or fruit. Large sori sit on the lower side of each frond. They start yellow or orange and turn dark grey. These clusters can make the upper leaf surface look bumpy. Gardeners grow this plant for its lasting green foliage. It suits rock gardens, shaded borders, slopes and old walls. It also forms ground cover beneath trees and shrubs. Deer tend to leave it alone.

Give it soil that drains well but holds some moisture. Sandy or loamy soil with humus suits it. Sources differ on light, from deep shade to full sun. Both support growing it with some shade. It tolerates dry shade and short spells without water. Water new plants through their first season and add mulch. Sources also differ on soil pH, supporting acid through alkaline conditions. The RHS rates it H7 for cold tolerance. NC State lists USDA zones 6–8. Divide plants in spring or early summer to make more. Remove dead or damaged fronds as needed. Outdoor plants have few pest or disease problems. NC State flags Florida fern caterpillar as one pest to watch.

The sweet root has served as food and in nougat. It has also been used to extend liquorice. PFAF notes an unpleasant smell and a taste that becomes sickening. The root has a long history in herbal medicine. Reported uses include digestive complaints and use as a laxative. External use may cause skin rashes. PFAF reports no known toxicity cases for this species. Its broader warning about ferns does not establish this plant's safety.