Blechnum tabulare (Thunb)

Family: Blechnaceae
Common name:
Mountain blechnum

 Young Blechnum tabulare

This is a large, attractive fern for the shady garden.

Ferns are neither Angiosperms (flowering plants) nor Gymnosperms (cone bearing plants). They do not produce flowers and fruits or seeds, but are spore producing plants. They are therefore referred to as Pteridophyta.

The genus name 'Blechnum' was derived from the Greek word 'blechnon' meaning a fern. The species name 'tabulare', is a direct reference to Table Mountain in Cape Town, the site where this fern was first collected between 1772 and 1774.

Blechnum tabulare has underground stems (rhizomes), which are erect, occasionally spreading and frequently massive. Rhizome scales are profuse, brown with a blackish-brown central stripe. They are 15 - 50mm long. The leaves, which are known as fronds, are arranged in whorls, and may be rigid. The leaf stalk is up to 300mm long and glabrous; except for tufts of scales at the base, which are similar to those found on the rhizome. This plant consists of sterile and fertile leaves. The sterile leaves are up to 1.4 x 0.35m long. Leaves are elliptic to oblanceolate in outline with the base comprising a series of much reduced leaflets. The leaflet bases are sessile. The margins of leaflets are entire. The texture is thickly leathery. The upper surface is glabrous with the undersurface sub-glabrous with the pale-brown hair-like scales set along the leaf margin.

There is considerable variation within Blechnum tabulare. They seem to vary according to the geographical distribution. The plants from the winter rainfall regions have a large stem and could be classified as mini-tree ferns. The leaves are more lax or arching. The plants from the summer rainfall areas seldom have a stem higher than 200mm and if they do, it is horizontal. The leaves are held more erect, and the leaflets are commonly tapering. The degree of scales on the underside of the leaflet also varies from north to south.

This fern is widely distributed from southern-western Cape through southern eastern Africa, to Zimbabwe, Mozambique, Malawi, Zambia, Angola, Tanzania, Kenya, Uganda, Zaire, Cameroon and Nigeria. Also on Madagascar, the Mascarene Islands and Tristan da Cunha.
It is commonly found growing in grasslands along streams, often in rank vegetation, on grassy hillsides, along the margins of evergreen forests and quite often on roadsides.

Blechnum tabulare can be confused with other species of Blechnum. In B.tabulare the bases of the pinnae are unequally shaped, a character not displayed by the other species. This fern is also frequently mistaken for a small cycad. The growth habit of these plants at a distance looks similar, although they are not at all related.

Growing in a shady place

Growing Blechnum tabulare

This plant can only be propagated from spores which disperse and germinate to form what is known as the prothallus, which is the sexual growth stage of a fern. The prothallus produces male and female organs where fertilization takes place and a new fern plant grows.

The mountain blechnum can be propagated from spores sown in a growing structure where adequate moisture can be maintained. The conditions have to be cool and moist. The growth media used must contain plenty of compost, leaf mould and should be well drained. This is however a very slow and time consuming process. It is advisable to buy a plant from a reputable nursery if you want quick results.

This is a very decorative garden fern or container plant. In the garden it must be planted in the semi-shade to full shade. It makes a beautiful foliage plant for a semi-shade spot on patio or verandah.

Plants are removed illegally from the southern Cape forests, and are sold as tree ferns, although this species is not related to the tree ferns, which belong to the family Cyatheaceae. Please assist in protecting our flora and do not buy plants if you suspect they have been removed from the wild.

 

References

  • Joffe, P.1993. The Gardeners Guide To South African Plants, Cape Town, Tafelberg Publishers.
  • Browse, P. M., 1979. Plant Propagation, Hong Kong, Reed International Books Ltd.
  • Burrows, J. E. 1990. South African Ferns and Fern Allies, Sandton, Frandsen Publishers.

Mhlonishwa D Dlamini and Thompson T Mutshinyalo
Witwatersrand National Botanical Garden

March 2002


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This page forms part of the South African National Biodiversity Institute's plant information website www.plantzafrica.com


 

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