Gymnosphaera capensis, synonyms Alsophila capensis and Cyathea capensis, (known as the "forest tree fern") is a regionally widespread and highly variable species of tree fern. It is indigenous to Southern Africa (subsp. capensis) and South America (subsp. polypodioides).
Both subspecies of Gymnosphaera capensis have a slender, erect trunk that is up to 4.5m (14.8feet) tall (occasionally even 6m (20feet)) and about 15 cm in diameter.[1]
The fronds are tripinnate, born on long stipes (stalks), and 2–3 m in length. The main stem of the leaf (rachis) is smooth to slightly warty and covered in scales that range from tan to brown or dark brown. The frond stalks are covered with dark brown or black scales.
The smallest leaflets (pinnae) have toothed (serrated) margins. The lowest pinnae may be separated from the others along the rachis and form a clump around the crown, similar to the "wig" of Gymnosphaera baileyana. This moss-like tuft of tiny, reduced leaves is distinctive for Gymnosphaera capensis, and can be used to identify this species across its range.[2] [3]
The sori occur in two rows, one along each side of the pinnule midvein, and are covered by scale-like indusia.
This fern is the only member of the family Cyatheaceae native to both Africa and the Americas. The species is divided into two subspecies:
Gymnosphaera capensis is cultivated as an ornamental plant.[4] It is relatively easy to grow if provided with a semi-shady, moist and sheltered environment, and can likely tolerate several degrees of frost.[4]