May in the hills with Barbara Mitcalfe and Chris Horne
Dicksonia squarrosa, whekī, rough tree fern
We hope you're enjoying the challenge of identifying in the bush the two tree-fern species which we described for you in the last two issues of the Tramper. Let's recap. - you've already learnt that:
- mamaku fronds have thick black stems which, when dead, drop cleanly off the trunk, leaving behind only octagonal scars;
- ponga fronds when dead, break off the trunk but leave behind thumb-thick, pale fawn, 15-cm-long pegs 'to hang your hat on'.
Now for your third tree-fern, Dicksonia squarrosa, whekī, rough tree fern. The fronds, when dead, break off, but leave behind on the trunk, 20-cm-long, skinny, black, stem bases, far too skinny to hang anything on.
Very rough to the touch, whekī fronds are dark green with paler green undersides, c. 3 m long , extending stiffly out from the trunk, not curving like mamaku fronds do. In the bush, you will have noticed the dead fronds, because even from a distance, they are a highly visible, easily identifiable, gingery-orange-colour, hanging down the trunk or lying on the ground, where they persist for a long time before decaying.
The Dicksonia genus may have evolved before the Cenozoic Era, which began about 65 million years ago. This would make it one of the most ancient fern genera still surviving today. Endemic to NZ, Dicksonia squarrosa can grow to c. 7 m tall, preferring moist sites in coastal or montane forest. It is common on the Three Kings, North, South, Stewart and Chatham islands, often forming groves, because it has the ability to reproduce by means of underground stolons which form new plantlets from buds at their tips. Also, if a whekī crown is damaged or killed by frost, it can sprout a new crown from the hairy, velvety buds on its trunk. This is why you will sometimes see whekī with 'two-storied' crowns. This unusual budding feature is of considerable use to landscape gardeners who know that just one, sawn-off whekī trunk can produce a whole fernery of whekī.
You'll be pleased to learn that there are only two genera of tree-ferns in the NZ flora: Cyathea and Dicksonia:
- Cyathea species have hairs and scales.
- Dicksonia species have only hairs.
Thus you can distinguish the genus of a tree-fern in the bush by checking whether the one you're looking at has fine hairs on its frond stems, (like cat or dog hairs), in which case it is a Dicksonia. If it has hairs and scales, (which are much broader than hairs, and often with tiny spikes), it is a Cyathea.
We have not found any references to rongoā (medicinal properties) in whekī. If you happen to know of any, we would be pleased to hear from you.