Pteridium aquilinum aka Northern Bracken Fern

Pteridium aquilinum, or bracken, is a fern in the Dennstaedtiaceae family. It grows back each year from spreading underground rhizomes. Its native range includes Europe, Siberia, Iran, and the Arabian Peninsula. It also includes Macaronesia and parts of northern and tropical Africa. Bracken is native to Britain and Ireland. It grows in woods, heaths, moors, and some grasslands.

Garden plants reach about 3.3–4.9 feet [1–1.5 metres] tall. Other accounts give heights up to 8.2 feet [2.5 metres]. Its large, finely cut fronds can span 3.3 feet [1 metre]. New shoots rise with curled tips, called croziers or fiddleheads. The fronds turn rusty brown in autumn, then die back. Creeping rhizomes let the plant spread far beyond each frond. A patch may exceed 26 feet [8 metres] across. Roots can reach about 3.3 feet [1 metre] deep. Bracken has no flowers and spreads by spores as well.

Bracken grows fast and can form thick stands of fronds. It grows in sun or shade, though sources differ on its light needs. RHS lists full sun and partial shade as suitable positions. Chicago Botanic Garden also lists full shade. Moist soil with good drainage suits it, but it tolerates drought. It grows in sand, loam, or clay. Acid to neutral soil is suitable; one source favours deep, acid sand. RHS gives it a UK hardiness rating of H5. Chicago Botanic Garden lists USDA zones 3–9.

Bracken gives wildlife shelter, and some moth caterpillars eat its fronds. It can serve as groundcover in woodland or poor-soil sites. Its spread makes it a poor choice for most gardens. Dense patches can crowd out much of the nearby growth. It may enter gardens next to open land. Division offers a way to raise new plants. It needs no routine pruning, though dead fronds can be removed. Sources report few pest or disease problems.

People harvest bracken for food, medicine, and useful materials. Young shoots appear in some local food markets. These uses do not mean that bracken is safe to eat. Reports link its leaves with cancer risk. Raw leaves and roots contain substances that reduce vitamin B1. All parts can poison horses, whether fresh or dry. Hay containing bracken can expose horses to these toxins. Long-term intake can cause weight loss, poor balance, and tremors. Severe poisoning can lead to death.