Forest Vines to Snow Tussocks: The Story of New Zealand Plants

Tussock Herbfield

Tussock Herbfield 136

This type of alpine vegetation occupies a zone about 500 m wide above the treeline where soils of adequate depth are present. The term 'herb-field' as applied to northern hemisphere mountains is defined as a complete cover of herbaceous alpine plants, but in New Zealand the
Figure 95 Red tussock grassland on Mt. Taranaki (Egmont).Tussocks with seed heads in foreground.Photo: J. W. Dawson.

Figure 95 Red tussock grassland on Mt. Taranaki (Egmont).
Tussocks with seed heads in foreground.
Photo: J. W. Dawson.

modified term tussock herbfield is preferred. This is because the dominant and conspicuous large tussock grasses belonging to the genus Chionochloa (Figs. 95, 96), although they lack woody tissues, are often as tall as or taller than some of the alpine shrubs.

Snowgrasses

The larger alpine tussock grasses, or 'snow grasses' as they are called, are frequently a metre high and sometimes as wide. Under good conditions they may reach head height at up to 2 m. Growth is slow and some of the larger specimens are estimated to be several centuries old. 137 The more or less hemispherical form of many of the snow tussocks confers on the mountain slopes a very distinctive and attractive texture reminiscent of that of cirrus clouds or, when the tussocks are tossed by the wind, waves of the sea. The colour of a snow tussock landscape is generally not green, but, depending on the species, ranges from a pale straw colour through shades of brown to a distinctly reddish shade. The lack of greenness results partly from the regular dying back
Figure 96 The snow tussock (Chionochloa macra) with flower heads of the spaniard (Aciphylla scott-thomsonii). Old Man Range, Otago.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.

of the leaves from the tips and partly to the presence of masking pigments. Heavy flowering seasons of the snow grasses are sporadic and often coincide with those of the beech species. This suggests that snow grasses too require a warm summer preceding flowering for the initiation of flower buds.

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).

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.

Spaniards

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 for 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).

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.

Mountain Buttercups 139

The largest and best known of these is Ranunculus lyallii, the so called 'Mount Cook Lily'. It seems that any large herb, especially if it has large, white flowers, as in this case, is inevitably and often erroneously
Figure 99 Flowers of Ranunculus lyallii at Arthurs Pass, Canterbury.Photo: J. W. Dawson.

Figure 99 Flowers of Ranunculus lyallii at Arthurs Pass, Canterbury.
Photo: J. W. Dawson.

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.

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.

termed a 'lily'. Ranunculus lyallii is most admired for its large, pure-white flowers up to 6 cm across (Fig. 99). It is equally remarkable for its large, rather floppy, almost circular leaves up to 30 cm in diameter (Fig. 100). Plants of this species may reach 1 m in height among tussocks or shrubs, particularly in moist places, throughout the South Island

mountains, except in the far north, and in Stewart Island. Other smaller, but still large, species have bright buttercup yellow flowers, for example the variable Ranunculus insignis throughout the axial ranges of the North Island and in the northern half of the South Island and R. nivicola in the tussock herbfield of Mt. Taranaki (Egmont) and also on the central North Island mountains. Ranunculus verticillatus, which is also yellow-flowered, is more slender and less conspicuous, but nevertheless common in the southern North Island and northern South Island. It often grows through, and is supported by, shrubs and snow tussocks.

Ourisia

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.

Mountain Daisies 140

Mountain daisies or celmisias are probably the most frequently encountered of our alpine herbs (Fig. 102). In other genera, two or three species may occur together at the same locality. Celmisias may have as many as five or six species occurring together. As befits the family Compositae, Celmisia flowers 141 are daisy-like and white with yellow to orange centres. In some species they may measure up to 7 or 8 or even 10 cm in diameter, The leaves are more diverse and remarkable than
Figure 101 (below) Gentiana bellidifolia. Mt. Peel, N. W. Nelson.Photo: J. W. Dawson.

Figure 101 (below) Gentiana bellidifolia. Mt. Peel, N. W. Nelson.
Photo: J. W. Dawson.

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.

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.

the flowers. In some species they are thin and soft in texture and sometimes sticky, but in many others they are very firm with hard upper surfaces and in colour range from grey-green through yellow-green to dark green. The most notable and attractive feature of many Celmisia leaves is a dense and often thick felt of hairs on the undersides and sometimes the upper sides as well. This tomentum, as it is termed, may be pure white, cream to buff or even bright rusty brown.

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.

Three genera of monocotyledons other than grasses may also be prominent in tussock herbfield and shrubland.

Bulbinella

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.

Mountain Flax

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.