Polystichum vestitum is a terrestrial fern with an erect and scaly rhizome, sometimes forming a short trunk and growing up to 700 mm in height.

Although it can form dense stands that often exclude other plants, it is more commonly found in conjunction with Stilbocarpa polaris, Poa foliosa and Pleurophyllum hookeri.

[6] The Prickly Shield Fern on the North Island is often found covering the hillsides and at higher altitudes where the climate is cooler, while on the South Island it can be found in a more varied range of habitats such as coastal and alpine regions, and at lower altitudes.

[11] The one spore cell can now divide into two and continue to develop into a small heart-shaped object called ‘prothallus’,[12] which looks very similar to a liverwort and can therefore be mistaken for it.

[11] Once fertilised, the cell can divide and the new baby fern starts to grow with help from the prothallus, which supports it with nutrients.

It prefers areas with more rainfall and can survive in temperature below 0°C, however, in these conditions the ferns are more often found under the forest canopy where it will be slightly warmer.

[8] On the underside of the fronds in silk tunnels, a tiny caterpillar of the "punui spore-eater" moth can be found living and eating the spores from the fern.

Vestitum has its origins from the Latin vestire and means "to be clothed", denoting the dense cover of the scales on its leaf stalks.