Blechnum tabulare fronds

Blechnum tabulare fronds of well-watered plants growing in shade are attractive, large and bright green. The frond petiole is up to 30 cm long and hairless, apart from some tufts of scales at the base, similar to those found on the plant’s rhizome.

The leaflets are sessile, alternating up the central stalk or rachis. The base lobes of the leaflet are unequal, useful in comparing Blechnum plants for identification purposes. The leaflet margins are entire although not very straight and sometimes wavy. The pale leaflet midribs are nearly bisecting the slightly glossy blades, in some parts straighter than the margins. 

The leathery leaflets are slightly twisted on the stalk, presenting the upper blade surfaces step-wise rather than with margins clashing, overlapping, touching or adjacent. A couple of fronds in picture are in a developmental phase with leaflets folded and pointing forward.

The plant bears two kinds of fronds: sterile ones that only function as leaves and fertile ones with brown sori on the lower surface. The sori are clustered, spore-producing receptacles, key to the propagation of new plants. Millions of spores may drop off the fertile fronds. In fact, the fern can be grown from sowing the spores in a suitable soil mix kept moist (iNaturalist; Wikipedia http://pza.sanbi.org).