Pteridium aquilinum subsp. aquilinum frond taking shape

The softest Pteridium aquilinum subsp. aquilinum frond tip parts in picture seen near Hermanus are white and still densely curled up. Growth means straightening and hardening of these alternate frond parts, eventually spaced in a slightly curved, smooth plane. All frond parts turn green for the annual growing season only. Sterile and fertile fronds have the same shape. The stem or stipe of a frond is up to 1 cm in diameter at the base.

Fronds arise singly from underground rhizomes, the winter-deciduous plant regrowing its above-ground parts every spring. The rhizomes from which the fronds grow are up to 15 m long, 5 cm in diameter and as deep as 3,5 m in the ground.

Dense colonies of genetically identical fronds tend to spread where conditions are favourable. Such colonies can become hundreds of years old, an individual rhizome older than 70 years. A colony studied in Finland was found to be 489 m in diameter and estimated from measured growth rate to be over 1400 years old (Bean and Johns, 2005; iNaturalist; Wikipedia).