Sticherus

Moderation may be a fine virtue, but not when it comes to Sticherus. With nature as our guide, it has become blatantly apparent to us that there can be no such thing as too much of this wonderful fern – having observed vast drifts of Sticherus flabellatus var. flabellatus on slopes, roadsides and river banks of Great Barrier Island, Northland and Coromandel.

Much of this genus’ appeal lies in the distinctive growth form of the Gleicheniaceae, whereby the rachis (stem) of each leaf forks to create intricate, regular geometric compositions. The aesthetic appeal of this leaf arrangement has brought Sticherus flabellatus to the attention of floriculturists in Australia, where discussion has shifted towards sustainable commercial production (as an alternative to wild harvesting¹).

Until relatively recently, 2 main species were considered to be native in NZ (S. flabellatus var. flabellatus and S. cunninghamii), with Sticherus tener (pictured below, within forest in Tasmania) present within botanical records as an intriguing outlier (from just one collection that Alan Mark made in Fiordland in the 1980s).

Subsequent investigation of Sticherus populations in the South Island identified a hitherto unknown occurrence of an Australian species in the northern South Island – Sticherus urceolatus. Previously misidentified as southern populations of S. flabellatus var. flabellatus (an understandable assumption given the similarities between the 2 species), S. urceolatus is now known from small populations in the Takākā area (where the image below was taken) and Denniston Plateau – with the spectre of mining representing a significant threat to it at the latter. Furthermore, knowledge of S. tener‘s distribution in NZ has improved, with its presence also being registered on the Denniston Plateau.

Of our four native species, three are shared with eastern Australia, whilst Sticherus cunninghamii is endemic to our shores. In common with certain species of Gleichenia (the genus to which our Sticherus spp. once belonged), S.cunninghamii is known by the evocative Māori name of tapuwae kōtuku – or ‘footprint of the heron’. This way of viewing the natural world extends to other names for Gleichenia species within Te Reo, which include waewae kākā (‘foot of the kākā’), waewae matuku (bittern) and waewae kōtuku.

Whilst S. cunninghamii shares Gleichenia species’ general disdain for cultivation, S. flabellatus var. flabellatus is an excellent, albeit slow-growing, garden plant, and the remaining 2 species are as yet little known in this country.

The botany of roadside banks is a matter of great interest here at O2. Sometimes this takes the form of strange, linear ‘fenceline floras’ of tōtara, Melicytus aff. alpinus or Coprosma rhamnoides – straddling the space between the assiduous attentions of livestock and road maintenance contractors.

In other cases, bare banks present opportunities for native ferns such as Sticherus flabellatus var. flabellatus to establish – especially where infertile conditions assist in keeping aggressive exotic grasses like kikuyu from overwhelming such habitats. In the Far North, where I have mostly observed roadside populations of S. flabellatus, it often grows intertwined with lycopods; especially the highly attractive Palhinhaea (syn. Lycopodium) cernua.

On Great Barrier Island, it is frequently associated with areas adjacent to watercourses (frequently growing in vast swathes), and we have observed S. flabellatus on riverine terraces in the flood zone of the Karangahake Gorge (at its southern limit). The species also shows a marked preference for kauri forest and sheltered coastal heathland, as noted by our friend, Marley Ford (a botanist with a remarkable knowledge of Northland’s flora and land environments).

Its tolerance of a wide range of conditions (from roadside banks in full sun to riparian forest habitats) holds true in cultivation, and we have found it to demonstrate considerable resilience as long as one starts with plants that are sufficiently large). That said, it establishes more rapidly in situations with consistent moisture and a small amount of shade.

Two varieties are recognised within the species; var. flabellatus and var. compactus. The latter is found in northern Australia, whilst the former variety occurs naturally in New Zealand, Australia, New Caledonia and New Guinea.