When I pass a garden with a tree fern, I always pause to admire the elegant form and lush foliage.
Our native tree ferns fall into two genera, Cyathea and Dicksonia. Colloquially, they are known as pungas. This is an English corruption of ‘‘ponga'', a Maori name for some species of Cyathea.
In the genus Cyathea are the ‘‘soft'' tree ferns. Among them are the iconic silver fern (Cyathea dealbata) and the queenly mamaku (Cyathea medullaris). The genus Dicksonia contains the ‘‘hard'' tree ferns. Their fronds are prickly to the touch.
The most common Dicksonia species is the slender-trunked wheki (Dicksonia squarrosa). Wheki is unique for its ability to resprout from the trunk if damaged. Beautiful living fences can be constructed from the trunks of wheki.
Tree ferns may seem delicate and shade-loving, but in nature they are often some of the first plants to colonise an area after a tree fall or slip. As long as they are given adequate moisture, particularly in their first few years, many tree ferns will handle a bit of sun and even a degree of exposure.
The best soil for tree ferns is rich and free-draining, so mimic the forest floor and provide them with a thick layer of compost mulch. They need a frost-free spot, and prefer some shade around the roots.
•Kate Caldwell is curator of the native plant collection at Dunedin Botanic Garden.
