Pentapogon (incl. Dichelachne)

“In these less constantly browsed and less heavily stocked uplands, plume-grass (Dichelachne crinita) and the two species of blue grass named are yet fairly plentiful.”

Tutira : The story of a New Zealand sheep station  (Herbert Guthrie-Smith)¹

What a sight that must have been in full bloom – pasture dominated by the waving flowerheads of Pentapogon (syn. Dichelachne) crinitus, along with the two native ‘blue grasses’ that Guthrie-Smith mentioned in his seminal text (Poa anceps and Trisetum lasiorhachis²).

Most New Zealanders are unaware that Guthrie-Smith’s 1921 account of the shifting natural history of a Hawke’s Bay farm is considered a classic amongst academics working worldwide in the field of environmental histories. The fact that ‘Tutira’ is held in such high regard is largely due to the eloquent and straightforward manner by which Guthrie-Smith recorded environmental change on the land that he farmed over decades.

Certain native grasses would have played a much greater role within pasture and grasslands in the early years of agriculture in New Zealand – before the continually evolving influences of machinery, fertiliser and irrigation moved these systems closer to monocultures. Biodiverse tracts of dry grassland still persist in some parts of the country (especially the eastern South Island), but many vanished grasslands must have had fascinating qualities (and species compositions) that have disappeared in the face of what is commonly termed ‘progress’.

Echoes of these can still be found on dry banks, ridgelines, woodland edges, high country farms, and disturbed ground within our cities. In the case of this genus, relictual populations of P. crinitus occur on the skeletal soils of coastal cliffs near the city centre, whilst P. inaequiglumis (pictured below, right) persists within the infertile, ‘unimproved’ soils of Waikumete Cemetery.

Pentapogon is a comparatively recent name for the attractive meadow grasses formerly known as Dichelachne, and all New Zealand species of Deyeuxia have also been transferred to Pentapogon. The net result of this taxonomic reshuffle is that we have 9 native species belonging to Pentapogon (a new genus to NZ botany); 5 of which are endemic to our shores.

The upper North Island exhibits a strong floristic connection with southeastern Australia, as demonstrated by the periodic arrival of interesting orchid species from across the Tasman in the Far North. This connection extends to the shared presence of several fern species (including Todea barbara and Cyclosorus interruptus) and a wide range of grasses – including Microlaena stipoides, Echinopogon ovatus, and 3 species formerly classified as Dichelachne.

We have an Australian client (with a background in ecology) to thank for bringing the potential of this grass to our attention whilst designing their garden. At the time, Pentapogon crinitus had never been used in landscape architecture here, but did have a track record of being cultivated in southeastern Australia.

Given that our background research was already partially focussed on floristic commonalities between NZ and eastern Australia, we were very interested in growing this species on from local stock. Long-hair plume grass has since featured in several of our projects, where the meadow-like quality that it brings to designs brings a sense of movement and lightness.

P. crinitus’ value as a component of pasture was commented upon by John Buchanan within his fine work from 1880, ‘Manual of the Indigenous Grasses of New Zealand’³, in which he wrote the following passage :

“A valuable grass, abundantly distributed throughout the islands, and forming, when in flower, a prominent feature in pasture. As a pasture grass when grown under favourable circumstances, on rich valley bottoms with perennial moisture, it is very succulent, but when on dry clay hills it is harsh and scanty; its nutrient qualities may be admitted, forming as it does a large constituent of pastures famous for fattening stock.

As a fodder grass it possesses considerable bulk, and would add much value to a mixed crop of hay. In sheltered situations near Wellington, this species has a very extended period of flowering, as a succession of scattered panicles may generally be found during eight months of the year.”

In his 1907 paper ‘The Grasses of Tutira’⁴, Herbert Guthrie-Smith provided even more detailed observations of P. crinitus’ role within seral fernland and grassland. One of the most interesting notes concerned P. crinitus‘ stature, which he measured at 5ft. 6in. within a largely unsuccessful experimental garden of native grasses. As a point of reference, that’s more than twice its normal height.

Guthrie-Smith also wrote about the long tenure that long-hair plume grass is able to maintain within bracken. It was one of the earlier species to return (via windblown seed) after burn-offs, and was the last grass to survive amongst dense fernland.

Despite its capacity to hold its ground amidst aggressive exotic grasses in rich soils (as evidenced by a fascinating note on experimental turf studies by Mr J. N. Williams of Frimley⁵), one now tends to encounter P. crinitus in what Guthrie-Smith termed ‘second-class lands’ – including clay banks/cliffs, drought-prone hill country, and dry or infertile meadows/pasture like the habitat pictured above (on the island of Motu Ariki within Lake Tekapo/Takapō).