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Summary

Platycerium bifurcatum, commonly known as elkhorn fern, is a species of epiphytic plant in the fern family Polypodiaceae. It is native to Australia and is widespread on the entire east coast.

Description

Platycerium bifurcatum is an epiphytic fern with dimorphic fronds, usually found growing on tree trunks and branches. The rhizome is short-creeping and much-branched. It is covered by the shield-like nest fronds (also called basal fronds or sterile fronds), which are more or less rounded and overlapping, and are appressed to the host tree. They can grow to about 45 cm (18 in) diameter. Their upper margins are deeply lobed and spreading, such that they trap organic litter which later becomes a nutrient source for the plant.

The fertile fronds (also known as foliage fronds) are markedly different. They are semi-erect becoming pendant, up to 90 cm (35 in) long, very narrow at the base and gradually widening. They fork two or three times, with the final segments being up to 30 cm (12 in) long and 3 cm (1.2 in) wide. Spores are produced on the undersides of these final segments.

Elkhorn ferns form a colony, with new plantlets growing from buds on the lower margin of the nest fronds. Nest fronds die back after reaching maturity but remain with the colony, curling inwards and retaining whatever litter they have collected, while roots of the colony members grow into them. In this way, with nest leaves building up and new plantlets on the exterior, the colony can grow to huge sizes.

A study published in 2021 attempted to determine whether the individuals in these colonies specialise for different roles. The researchers found that the foliage fronds (called "strap fronds" in the study) of colony members near the bottom are less likely to produce spores than those of members near the top of the colony. They also found evidence that the nest fronds of lower members absorb more water than those of the members above them –...