Platycerium coronarium is one of the largest ferns in the family Polypodiaceae. It is an erect epiphytic fern that lives on large trees. It is commonly known as the staghorn fern due to the shape of its fertile fronds which resemble stag's horns. The species is locally known as paku langsuyar or tanduk rusa (Malay) or keruin (Temuan).
Platycerium coronarium is widely distributed in Myanmar, Thailand, Cambodia, Vietnam, Sumatra, Java, Peninsular Malaysia, Singapore, Borneo and the Philippines. It is widespread in Peninsular Malaysia but under-collected due to its huge size (Hovenkamp, 2013). This fern can commonly be found growing under light shade or in full sun, in the lowlands or hills, up to 1000 m altitude.
Platycerium coronarium attaches to tree trunks, mostly old trees. It produces two kinds of fronds, namely, nest fronds which are broad and upright in habit, and form a "basket", and fertile fronds which are narrow, pendulous and variously dichotomously forked. Young plants produce only circular nest fronds to cover the rhizome and roots, while old plants eventually encircle the tree trunk or branch. This species exhibits the nest mechanism. The nest fronds form a basket and trap leaf litter which decomposes into humus that retains water and nutrients, to be supplied to the roots (Hovenkamp, 2013).
In Peninsular Malaysia, three species of Platycerium are recorded, namely, P. holttumii, P. coronarium and P. ridleyi. The differences between these species are as follows: P. holttumii has two or more soral patches on each fertile frond and its scaly rhizome scales do not have a wide flabelloid margin; P. coronarium and P. ridleyi have a single soral patch on each fertile frond and their rhizome scales have a wide flabelloid margin. In addition, P. coronarium has long and pendulous fertile fronds and its fertile lobes are semi-circular to kidney-shaped compared to P. ridleyi which has erect fronds and fertile lobes which are obovate or elliptical, or rarely lobed.
Platycerium coronarium is unique because it is a large epiphyte that grows in clusters whereas P. holttumii and P. ridleyi grow solitarily. The rhizome scales are basifixed, about 15-35 mm long and 4-10 mm wide, margin with short hairs and a rounded apex. The nest fronds are sessile, green in colour, recurving when old, up to 50-110 cm long and 25-55 cm wide, and erect at its upper part. The fertile fronds mature serially. They are asymmetrical and 50-125 cm long or longer. The fertile fronds are 3-7 times forked with 4 main lobes. The main veins are prominent and dichotomous while the secondary veins form a conspicuous network. The central sterile lobes are elongated and pendulous, while the central fertile lobes are stalked, simple, semi-circular to kidney-shaped and horizontal, about 7-36 cm long and 5-20 cm wide. The stalk is 2-9 cm long. The soral patch fully covers the fertile lobe (Hovenkamp, 2013).
Platycerium coronarium is commonly cultivated in the garden and is popular as an ornamental due to its uniquely shaped fronds. As for its conservation status, P. coronarium is categorized as Least Concern (LC), (Hovenkamp, 2013).
