Cyathea deckenii is a species of tree fern native to the Democratic Republic of the Congo, Tanzania and Mozambique, where it grows in wet forest at an altitude of 1350-2300 m. The trunk is erect and up to 10 m tall. Fronds are bipinnate and 2-3 m long. Characteristically of this species, the most basal one or two pairs of pinnae are reduced. The rachis and stipe range in colour from brown to dark brown or black-brown and are sparsely covered with a few scales. The scales are dark and narrow with a fragile margin of variable width. The stipe also has conical warts near the base. Sori are round and covered by large, thin indusia.