Poa

“Gras ist das Haar der Mutter Erde.”

Karl Foerster, in “Einzug der Gräser und Farne in die Gärten”

This well-known statement, made by Karl Foerster in his seminal publication on the introduction of grasses and ferns into gardens, translates to “Grass is the hair of Mother Earth”. This observation is borne out of the fact that grasses form the dominant vegetation cover in many natural landscapes (especially in Foerster’s Europe), and are also the mantle of choice for human agriculture and horticulture.

One genus that epitomises the adaptability of grasses is Poa, the members of which occupy an extremely wide variety of habitats, from the Subantarctic Islands to alpine tussocklands, highway cuttings, pasture, and suburban lawns. These exhibit a large range of growth forms, from the short-lived, diminutive Poa annua (an exotic weed that makes an annoyance of itself in lawns) to the huge tussocks of Poa litorosa in which albatrosses nest on our Subantarctic Islands.

Poa is a large genus, with around 500 species worldwide – c. 40 of which are native to New Zealand. The majority of people are most likely to encounter two exotic species of Poa in everyday life; the aforementioned Poa annua and Kentucky bluegrass (Poa pratensis), a grass that is widely used in pasture and turf.

Of our native Poa spp., silver tussock (P. cita) is the most commonly planted species – due to its attractive appearance and its tolerance towards dry, exposed habitats (such as the hillside at Sandymount, on the Otago Peninsula, shown above).

This plant also delivers considerable wildlife benefits in many areas, as a host species for insects – like the tussock butterfly pictured above. Other species that have been grown in gardens include blue tussock (Poa colensoi), blue shore tussock (Poa astonii), broad-leaved poa (Poa anceps) and sand tussock (Poa billardierei, in the image below, a grass that was until recently known as Austrofestuca littoralis). A low-growing, fine-leaved species called Poa pusilla has also been recently introduced into cultivation by Oratia Native Plant Nursery.

The name, Poa, is derived from the ancient Greek word for meadow or pasture grass¹.

Sometimes, the most evocative images that one can view in nature occur in highly modified environments. That is the case with this weeping grass, which forms elegant sheets of drooping foliage on moist highway cuttings in parts of New Zealand. With its vivid green colour and neatly arranged fans of broad leaves, it makes for an understated, yet impressive, sight.

Poa anceps naturally grows in a variety of habitats, including forest and scrub. However, I associate this plant most strongly with cliffs and banks – such as the coastal cliff pictured below, from the southern side of Kawhia harbour. P. anceps can be found growing up to reasonably high altitudes, although it is especially prevalent in coastal areas of warmer parts of New Zealand (it is absent from New Zealand’s southernmost regions, where other related species occupy similar niches).

Broad-leaved poa is noted as a variable species within the wild; and as such, it is a good example of the value of selecting particular forms, that are either best suited to local conditions or have especially desirable characteristics.

For example, one form that we have trialled (from the vicinity of Whangaroa Harbour) exhibits greater tolerance towards drought than other forms that we have planted. It was sourced from parent material that was naturally growing in an exposed position, where it simply wouldn’t have survived if it had possessed a weaker disposition. We have also noted that P. anceps endures drought well in Nelson, where we have specified significant numbers of it, especially when given a degree of afternoon shade. Poa anceps frequently grows in positions where water seeps down cliffs and banks – and is therefore more dependent on a consistent supply of moisture.

P. anceps is a valuable garden plant for northern parts of New Zealand, where many grasses and sedges that are promoted for cultivation do not endure in the long term (as they commonly hail from more southern climes). As noted previously, it will perform best when it is provided with moisture at dry times of the year. This can be achieved by positioning it where water collects, such as at the base of slopes or adjacent to large rocks.

Where it is placed at the edge of plantings, P. anceps offers a similar character to a Japanese grass, Hakonechloa macra (the green form thereof), which is a popular garden plant in many countries. Like H. macra, Poa anceps brings a strong sense of horizontal movement to planting associations. In addition to its attractive growth form and foliage, it also bears graceful buff-coloured flowerheads, that stand above the foliage in early summer. It receives its specific epithet, ‘anceps‘, from its stems (or culms as they are called in grasses) – that Latin term means ‘double-sided’, in reference to the flattened culms¹.