Platycerium holttumii

Platycerium holttumii is an accepted naturally occurring species in Polypodiaceae, separate from the Philippine species P. grande.

K.U. Kramer de Joncheere and E. Hennipman published the species in 1970 and named it for the botanist and fern specialist Richard Eric Holttum.

The native range extends from southern Yunnan through Cambodia, Laos, Thailand, and Vietnam to Peninsular Malaysia.

The species grows on tree trunks in lowland monsoon forest and is described as rather rare in the regional account.

Platycerium holttumii normally grows from one growing point and forms a very large basket of overlapping shield fronds.

Shield fronds are approximately 90–115 cm long and 90–135 cm wide, with upper portions divided three to six times into roughly equal lobes and a conspicuous lower fringe.

Mature fertile fronds are produced in pairs and divide into two unequal main lobes, each bearing a broad horizontal spore-producing patch.

The combination of a solitary giant basket and paired fertile fronds with two clearly unequal main lobes helps distinguish P. holttumii from P. grande, whose paired fertile fronds are more evenly divided.

DNA-based phylogenetic research recovered P. holttumii and P. grande as sister species within the Old World lineage of Platycerium.

Spores have been grown through germination, gametophyte development, fertilization, and young sporophyte formation under laboratory conditions.

Malaysia’s national plant Red List assesses P. holttumii as Critically Endangered under criterion B2ab(iii) within Peninsular Malaysia.

The Care Book describes Platycerium holttumii’s shield and fertile fronds as relatively thick and firm, with sparse star-shaped hairs.