Forest Vines to Snow Tussocks: The Story of New Zealand Plants
Figure 95 Red tussock grassland on Mt. Taranaki (Egmont).
Tussocks with seed heads in foreground.
Photo: J. W. Dawson.
Figure 96 The snow tussock (Chionochloa macra) with flower heads of the spaniard (Aciphylla scott-thomsonii). Old Man Range, Otago.
Photo: J. W. Dawson.
The flower and seed heads of some of the larger snow tussocks are quite diffuse, and their very slender stems and small, scattered, pale, flower or seed heads give an insubstantial misty effect similar to that of the garden Gypsophila, so popular in flower arrangements. On the wetter western mountains of the South Island the broadleaved snow tussock (C. flavescens), can grow sometimes 2 m high, and dominates in the zone 200 m above treeline. The mid-ribbed snow tussock (C. pallens) is often present, generally on younger, better drained soils. Both species are also common on the North Island axial ranges. With increasing altitude on the wet South Island mountains the two large snow tussocks gradually give way to the much smaller curled snow tussock (C. crassiuscula).
Figure 97 Dense cover of red tussock (Chionochloa rubra) on a swampy valley floor. Near Boulder Lake, north-west Nelson.
Photo: J. W. Dawson.
On the drier eastern South Island mountains in the southern half, the dominant snow tussock in the low alpine zone is the narrow-leaved snow tussock (C. rigida). This gives way at higher altitudes to the smaller recently described slim snow tussock (C. macra). Only slim snow tussock extends north of the central South Island and it then occupies a broader altitudinal zone.
Among the smaller species of Chionochloa, which are found mostly at higher levels in herbfield, carpet grass (C. australis) is worth a special mention. As its common name indicates it does not have a tussock habit, but forms thick, often extensive swards. The needle-like leaves are dark green and shiny and as they are also slippery and tend to lie downhill, they need to be walked on with care. Carpet grass is found on wetter mountains in the northern third of the South Island.
Where snow tussocks are tall and dense near the treeline one might think there would be little room left for other alpine herbs; in fact there are quite a number. Some are small and inconspicuous, enjoying the shelter and tolerating the shade of the tussocks. Others are much more conspicuous and could be termed large or even giant herbs approaching or exceeding the tussocks in height.
Notable among the large alpine herbs are the Spaniards or speargrasses belonging to the genus Aciphylla of the Umbelliferae (carrot family).138 Nothing could look more unlike a carrot plant than the larger spaniards of tall tussock grassland. In their tussock-like clumps the large leaves are deeply divided into hard, rigid segments tipped by needle-sharp spines. The flower, and later seed, heads are equally unusual in that, instead of being broad and open as is more typical for the family, they are dense, narrow and lance-like. The individual flower clusters, densely aggregated on the upper parts of the lances, are exceeded in length by their associated bracts. These bracts have segments as spiny as those of the leaves. Having suffered while collecting specimens of such spaniards page 175for study, I am inclined to agree with the suggestion that the excessive spininess is a defence against browsing animals (and botanists), which in pre-human times in New Zealand would have been the moas. However, despite their unpleasant characteristics, many of the spaniards are striking in appearance and, when strongly coloured, decidedly handsome as well. Some species have grey-green leaves and flower heads ranging from green to pale yellow, others have both leaves and flower heads with a quite strong yellow to orange colouration as, for example, in the golden spaniard (Aciphylla aurea) (Fig. 98).
Figure 98 The golden spaniard (Aciphylla aurea) scattered through tussock grassland comprised of narrow-leaved snow tussock (Chionochloa rigida). Mt. St. Bathans, Otago.
Photo: J. W. Dawson.
The golden spaniard, A. aurea, is often prominent in drier habitats in the eastern South Island and is characteristic of narrow-leaved snow tussock grassland (Fig. 98). In higher herbfield where the plant cover is shorter the larger species of Aciphylla give way to smaller forms. Some of the smaller forms are spiny with narrow inflorescences; others are more like the related Anisotome with soft leaves and broad inflorescences.
It is difficult to understand why narrow dense inflorescences should have evolved in Aciphylla. It could be seen as a protective device as the short flower clusters are readily shielded by the spinescent bracts, but similar (although not spiny) inflorescences occur in quite unrelated plants elsewhere in the world — the tree Senecios and Lobelias of the central African Mountains, the Puya (Bromeliaceae) of the northern Andes, Echium in the Canary Islands and the grass trees (Xanthorrhea) in Australia, to name a few.
Figure 100 Group of alpine plants at Arthurs Pass, Canterbury. The large circular leaves are Ranunculus lyallii. Two mountain daisies are present, C. semicordata below and C. armstrongii above. The herb with very divided leaves is Anisotome haastii and the long silvery leaves at the top belong to Astelia nervosa. The needle-leaved shrubs are Dracophyllum longifolium.
Photo: J. W. Dawson.
The Ourisias are sometimes called mountain foxgloves. This is a common name with at least some validity since foxgloves and Ourisia belong to the same family, the Scrophulariaceae.
The two large species of Ourisia found in tussock herbfield, like the large Ranunculus species, have leathery or somewhat fleshy, dark green leaves. The flowers are white with yellow centres, 2-3 cm across and have the five petals fused at the base. The flowers are distinctively arranged in spreading circles or whorls, one above the other. Ourisia macrophylla with two subspecies is found on wetter mountains in the North Island and O. macrocarpa also with two subspecies in similar sites throughout the South Island.
To those familiar with the brilliantly blue, deeply bell-shaped gentians of the northern hemisphere, the New Zealand versions must come as a surprise. Their flowers are like sprinklings of snow among the tussocks and in each flower the petals are much more deeply divided than those of northern species although still fused near the base (Fig. 101). The leaves are generally somewhat fleshy and sometimes both leaves and stems have a strong red or purple colouration masking the green. The flowers are usually pure white, but sometimes have purple veins. The distinctions between many of the New Zealand species are still not clear, but several are prominent in tussock herbfield and shrubland. Gentiana corymbifera can be up to half a metre tall and is mostly found in drier eastern tussock grassland throughout the South Island mountains. The similar G. montana is widespread in the wetter, mostly western mountains of the South Island and in Stewart Island. G. bellidifolia, a page 179somewhat smaller species, ranges throughout the mountains of both North and South Islands.
Figure 102 (right) A group of celmisias in flower —
C. semicordata. There are a few non-flowering rosettes of C. traversii also. Mt. Arthur, N. W. Nelson.
Photo: J. W. Dawson.
Some celmisias of tussock herbfield have their leaves in one or more rosettes close to the ground. Others, which form in patches, have closely branched, spreading stems with more dispersed leaves. The stems of some of the latter can be fairly woody, and when they are semi-erect, the plants could be described as dwarf shrubs.
Celmisia semicordata (Fig. 102) has the largest leaves and flowers of the genus. The leaves are in large rosettes and are silvery green with white undersides. The species is common in both open shrubland and tussock herbfield on wetter mountains throughout the South Island except the far north. Celmisia verbascifolia, with a similar range to C. semicordata, and C. traversii in the north-west and south-west of the South Island are similar in habit, but somewhat smaller than C. semicordata. Celmisia verbascifolia is notable for the bright purple petioles and midribs of its leaves and C. traversii for the deep, velvety rusty red tomentum on the leaf undersides. The commonest Celmisia in New Zealand is C. spectabilis, which in some of its forms is like a small C. semicordata. It occurs throughout the mountains of the North and the northern half of the South Island in both wet and dry tussock grassland. It becomes particularly abundant following fires.
Three species are similar in having tufts of long, narrow, pointed sword-like leaves, which leads to them sometimes being mistaken for spaniards (Aciphylla). Celmisia lyallii ranges along the eastern sides of the South Island mountains in Chionochloa macra grassland, and C. petriei and C. armstrongii together span the wetter western mountains of the South Island, C. petriei in the north-west and south-west and C. armstrongii in between.
Of the many smaller leaved species which form spreading mats a metre or more in diameter, Celmisia incana is probably the most striking as it often has a completely white tomentum of hairs on both sides of the leaves as well as the flower stems. It ranges throughout the North Island mountains and continues to the middle of the South Island.page 181
Three genera of monocotyledons other than grasses may also be prominent in tussock herbfield and shrubland.
Species of this genus may be abundant on moist, shady slopes in tussock herbfield, their heads of starry yellow flowers often providing something unusual in New Zealand mountain landscapes — a mass of solid colour. Their leaves are tufted and long and narrow. Bulbinella hookeri ranges from the North Island mountains to north Canterbury; B. angustifolia, sometimes inappropriately known as 'Maori onion', ranges through the drier eastern mountains of the South Island from North Canterbury southwards; and B. gibbsii in the wetter mountains of the southern North Island, southern South Island and Stewart Island.
The term 'flax' for the genus Phormium, although firmly established, is yet another inappropriate common name as Phormium and the true linen flax (Linum) have in common only the possession of useful fibres. Mountain flax is Phormium cookianum and its tufts of narrow, leathery leaves may be conspicuous in poorly drained places in tussock herbfield and shrubland. The flowers in its quite tall heads vary in colour, from plant to plant, from yellow to dark reddish purple.
The thirteen New Zealand species of Astelia are about equally divided between the forests and the mountains. The flower heads of the smaller alpine species are short and inconspicuous, but their bright red to orange berries are strikingly attractive. Two large species may be conspicuous in wet places in tussock herbfield and shrubland. Astelia nervosa (Fig. 103) found throughout the country, has tufts of leaves up to a metre or more in length, varying from pale green to silvery white. In the latter case the leaves look as if covered with frost. Astelia petriei, with shorter, broader, pale green leaves, grows on the higher rainfall mountains of the western South Island. The smaller, patch-forming Astelia nivicola has a similar range but at higher altitudes in herbfield. The smallest herbfield species is the grasslike Astelia graminea, which is especially common among carpet grass (Chionochloa australis) in the northern South Island.page break