Forest Vines to Snow Tussocks: The Story of New Zealand Plants
Chapter 8 — Alpine Plants
Internationally, the treeline is generally taken to be the lower limit of alpine vegetation. In New Zealand, where beech species are present, the treeline may be very clearly defined with the trees abutting directly onto either alpine tussock grassland, with or without an admixture of shrubs, or a narrow belt of shrubs which widens on steep, sunny, stony slopes and spurs. Where beech species are not present the treeline formed by montane conifer broadleaf forest species is both more diffuse and at lower altitudes than that of beech at comparable latitudes. Above such treelines there is usually a very wide zone of shrubs extending up slope for 1-300 m.133 Some consider that this zone is climatically suitable for beech forest and so refer to it as 'subalpine shrubland' implying that the climatic or 'regional' treeline lies at the upper limit of the shrubs. As a modification of this view, Wardle95 suggests that the regional tree line would lie at the upper limit of shrubs capable of becoming small trees. This implies that below such a line the shrubland is subalpine and above it alpine (Fig. 90).
It seems more convenient to treat the higher altitude shrublands as one entity and for this reason I use the non-committal term 'mountain shrublands'.
Figure 91 Mountain shrubland on Mt. Taranaki (Egmont). Beech (Nothofagus) forest does not occur on this mountain.
Photo: J. W. Dawson.
Subalpine Shrubs or Small Trees
In the lower or subalpine parts of the shrub zone the species composition depends on soils and aspect. In the Westland beech gap Wardle134 recognises a number of subalpine low forest or shrub communities which are in part typical for New Zealand as a whole. They include:
Hoheria glabrata low forest
Hoheria glabrata or mountain ribbonwood colonises young, deep, moist, well-drained and often stony soils such as those provided by slips, talus slopes and alluvial fans. This small tree, being one of the few in New Zealand that is strongly deciduous, has attractive yellow to red leaves in the autumn. Its clusters of white flowers, each up to 4 cm across, are also a striking feature. Olearia ilicifolia (the holly-leaved daisy tree) also contributes to the canopy and the ground beneath has a dense cover of the fern Polystichum vestitum.
Dracophyllum-Olearia Low Forest and Scrub
This occupies similar but older sites than Hoheria glabrata low forest. Dominance is shared by the mountain ribbonwood (low forest only), Dracophyllum longifolium (scrub only), D. traversii and Olearia lacunosa, the last two being up to 7 m tall. The genus Dracophyllum, although belonging to the dicotyledon class of the flowering plants has long, narrow, parallel-veined leaves similar, in the larger examples, to those of such monocotyledons as the cabbage tree (Cordyline australis) or even the pineapple. Indeed, mountain groves of Dracophyllum traversii are sometimes known locally as 'pineapple forests'. This species with its candelabra-like form, and its sword-like leaves forming a deep litter on the forest floor, is certainly the most distinctive member of the community.
Olearia lacunosa also has narrow, although net-veined leaves, which are somewhat like those of juvenile lancewood (Pseudopanax crassifolius). Some of the other shrub species with relatively large thick leaves are Griselinia littoralis (broadleaf), Pseudopanax colensoi (mountain five-finger) and Olearia colensoi (leatherwood). Pseudopanax simplex has somewhat page 167smaller, thinner leaves and Myrsine divaricata and Coprosma pseudocuneata have very small leaves. Prominent ground plants are Blechnum 'procerum' and the tussock-like Astelia nervosa.
Dominance of the shrub species varies from place to place in this community type, but it is at its most impenetrable where Olearia colensoi with its stiff almost cardboard-like leaves predominates, as in the North Island ranges, the westernmost coastal ranges in the South Island and in Stewart Island.
This occurs on old, leached infertile soils and is a low shrubbery from 0.5 to 1.5 m tall in which the small conifers Halocarpus biformis and Phyllocladus aspleniifolius var. alpinus (mountain celery pine) share dominance with Olearia colensoi and Dracophyllum longifolium.
Both the conifers also occur in the lowlands of Westland where they become small trees. In the greyish-green mountain celery pine, what appear to be fan-like or rhomboidal leaves are in fact flattened branchlets termed phylloclades.
These are some of the community types of subalpine shrubs and small trees, but there are a number of others related to special habitats or resulting from disturbances, whether caused by nature or by humans. Many of the species of these communities may grow in the montane forests especially towards their upper limits.
Above the actual or inferred treeline come shrubs that can be considered truly alpine, although many descend to lower altitudes in open habitats. Immediately above treeline on moderate slopes with a reasonably well developed soil such shrubs generally intermingle with large tussock grasses and other herbs in what has been termed tussock-shrubland. As altitude increases, the shrubs decrease and the herbs increase. On steeper slopes, such as spurs and ridges, with shallow, stony soils, species of shrubs mostly different from those of the tussock-shrubland may form a more continuous cover, but there is usually a herb component. On these rocky sites certain shrubs may extend to quite high altitudes, becoming shorter and more scattered as they do so.page 168
It is in this higher shrubland zone that New Zealand's largest genus Hebe attains its greatest prominence. Of the approximately 60 commoner species of alpine shrubs 24 or 40 per cent are hebes, many of them exhibiting the symmetry of form and attractiveness of foliage — grey-green, yellow-green and shades of yellow and orange — that have made the genus so well known horticulturally in many parts of the world. The alpine hebes can be divided into two approximately equal groups contrasting strongly in growth habit. In the first group the leaves, although short and fairly broad, are spreading and often very precisely arranged in four vertical rows. The shapes of such shrubs may be so symmetrical and their surfaces so dense, that they appear to have been trimmed to shape. Appropriately, one of them has been named Hebe topiaria. The relationship of the hebes in this group with the willow-leaved species (koromikos) of the lowlands is quite evident, but with the second group of so-called 'whipcord' hebes this is not so; they resemble instead the quite unrelated scale-leaved conifers (Fig. 93). It is no surprise to learn that one of them is named Hebe cupressoides. Both growth forms are represented in tussock-shrubland and on stony ridges.
Similar in general appearance to the hebes with spreading four-ranked leaves are a number of species of Pimelea or New Zealand 'daphnes'. The flowers with their pairs of stamens are also quite Hebe-like, but as a general rule the two genera can be distinguished by the presence (Pimelea) or absence (Hebe) of leaf and flower hairs. Pimelea leaves often feel quite silky to touch. Pimeleas occur both in grassland and on rocks.
Most of the alpine dracophyllums have needle leaves. Taller species in tussock-shrubland have a switch-like habit with narrow branching angles, others in similar habitats or on rocky ridges are more or less prostrate. During the colder period of the year especially, the dracophyllums add colour to the alpine scene when their leaves develop bright reddish brown hues.
Figure 94 (right) Gaultheria depressa. The upper fruit has had part of the fleshy calyx removed to reveal the seed capsule.
Photo: M. D. King.
All except one of the relatively few shrubby alpine coprosmas have very small leaves and slender twigs. Three of these are prostrate and scrambling, C. cheesemanii and C. crenulata in damp places in tussock grassland and C. depressa on rocky sites. Coprosma pseudocuneata with its attractive, strongly recurved, yellowish green leaves has an erect habit and extends to quite high altitudes in sheltered rocky sites. The one large-leaved Coprosma, C. serrulata, grows in shaded tussock shrubland page 170 and also on shaded rocky bluffs. Its leaves are thick and leathery with prominent veins.
The Compositae or daisy family is represented by a few species belonging to three genera.
Brachyglottis (Senecio) bidwillii is widespread in tussock shrubland and on rocky bluffs. Its leaves are rounded and very thick with a thick, feltlike mass of hairs on their undersides. Two other species are more localised, B. adamsii in adjacent parts of the North and South Islands, and B. revolutus in the south-west of the South Island.
The genus Helichrysum, which includes the flowers known as 'everlastings', has several shrubby alpine species in the drier eastern mountains of the South Island where they grow on rocky outcrops and ridges. They all have a similar distinctive appearance with scale-like, but somewhat swollen, strongly convex leaves closely pressed to the stems. The rounded backs of the leaves may be very shiny and each leaf is surrounded by a dense mass of white hairs. The most robust and striking species is Helichrysum coralloides with cylindrical stems up to 1 cm in diameter.
Cassinia vauvilliersii may be common in tussock-shrubland throughout New Zealand as well as in open vegetation at lower altitudes. It is an erect shrub, often with a distinct yellowish colouration from the hairs on the undersides of the small leaves.
Melicytus (Hymenanthera) alpinus of the violet family is a small shrub with short, stiff, interlacing twigs which are almost spiny at the tips. The species occurs throughout the South Island and is most frequent on rocky ridges and outcrops.
Myrsine nummularia is a small-leaved, prostrate, thin-stemmed shrub found throughout the New Zealand mountains where it favours rock outcrops and open places in tussock grassland. Its most striking feature is the bright violet-blue colouration of the berries.
Three dwarf conifers may be frequent throughout tussock shrubland. Snow totara (Podocarpus nivalis) forms low bushes in this community, but is also common at scree margins and on moraines at lower elevations. The pigmy pine (Lepidothamnus laxifolius), sometimes called the smallest conifer in the world, forms even lower mat-like patches in poorly drained sites and the mountain celery pine (Phyllocladus aspleniifolius var. alpinus) is still erect in habit though shorter than it is in the subalpine shrublands.
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
Bogs develop in the subalpine and low alpine zones where drainage is poor.143 Suitable sites are hollows formed by glaciers and flat areas under high rainfall conditions on glacial terraces, mountain passes and flat topped mountain ridges. Where rainfall is high, rain may provide most of the water in the bogs, but in drier eastern areas drainage from the surrounding slopes makes the major contribution. When the water table is near the surface, the dominant plants in the bogs are of cushion form. Cushion plants are freely but closely branched; and the ultimate twigs, with their upper living and lower dead leaves, are so closely pressed together lengthwise that the exposed tips of the living leaves form a firm, continuous, often unyielding surface. Many cushion plants can be stood on without suffering any visible effects. The leaf tips of each ultimate branchlet may form a circular pattern or be compressed into an hexagonal shape. Depending on the species the cushions range from a few centimetres to a metre or more in diameter. They are broadly convex to almost hemispherical in form and are separated by shallow to quite deep hollows.
A number of sedges and related plants occur in mountain bogs throughout the country. The Centrolepis and Gaimardia species form soft moss-like cushions; Oreobolus pectinatus with its leaves distinctively arranged in two rows in one plane forms a firmer cushion while other species of the genus form flat mats. Of other cushion plants, Donatia novae-zelandiae forms much larger, broadly convex, extremely dense cushions whose dark green leaf tips contrast strongly with the numerous, small white flowers in season (Fig. 104). It occurs from the southern North Island southwards and also in the Tasmanian mountains.
As well as the cushion plants there may also be prostrate but less compact dwarf shrubs including Dracophyllum muscoides, D. politum and the pigmy pine (Lepidothamnus laxifolius). In the hollows between the cushions and prostrate shrubs are a variety of small sedges and mosses and small species of several large genera including Astelia linearis with its red jelly bean-like fruits, Celmisia glandulosa, Gentiana lineata (in the far south) and dense mats of Coprosma perpusilla (formerly C. pumila) Several species of the insect catching sundews (Drosera) with their glistening leaf glands are also frequently present.
In the highest parts and margins of bogs, red tussock (Chionochloa page 184 rubra) may often be found. In the lowest, wettest parts, soft masses of the yellow-green bog moss (Sphagnum) predominate.
On the higher, steeper mountains, particularly of the South Island, herbfield gives way with increasing altitude to fellfield (Fig. 105). As a result of the severe environmental conditions in this zone, plants of this type of vegetation are both sparse and specialised. They are subjected to low average temperatures, heavy frosts, deep snow for part of the year, violent winds, and at times strong sunshine, which may raise the temperature of the extensive areas of exposed rock very considerably. Erosion by frost action and wind is quite rapid particularly on the greywacke sandstone of the Southern Alps and other axial ranges. The resulting angular fragments may form a thin layer of debris on ridge crests and sides; but gravity, assisted by wind and, more dramatically, avalanches, constantly moves the products of erosion downslope, so there is little opportunity for the development of even thin soils. Rock outcrops and bluffs in this zone provide more sheltered and secure sites for plants. Nevertheless a number of them do establish away from outcrops, especially in deeper debris on moderate to gentle slopes. Of these, some are small prostrate Hebe shrubs which are also to be found on rock outcrops. They are not of the whipcord type, but have small rounded leaves arranged in attractive patterns. Hebe haastii and H. epacridea (Fig. 106) are yellow or orangey-green; H. petriei is grey-green. Small herbs are more common — several diminutive grasses and sedges, and one to several species of Epilobium, Ranunculus, Celmisia, Gentiana, Myosotis and Parahebe. Small cushion plants also occur; these include Hectorella caespitosa, the softly pubescent species of Chionohebe, Phyllachne colensoi, and sometimes extensive mats of the silver grey Celmisia sessiliflora.
Figure 107 A rock in fellfield on the crest of the St. Arnaud Range, northern South Island. Frost action has formed fissures in the rock where small cushions of Colobanthus canaliculatus (left) and Raoulia bryoides (centre and right) have established.
Photo: J. W. Dawson.
Figure 108 Large cushion of the Marlborough vegetable sheep, Haastia pulvinaris. Mt. Cupola, Nelson Lakes National Park.
Photo: J. W. Dawson.
Figure 109 Close view of a portion of a Haastia pulvinaris cushion showing the branchlet tips closely invested by woolly leaves. Photo: J. W. Dawson.
Two spaniards (Aciphylla) are notable cushion plants in fellfield. A. dobsonii in South Canterbury and North Otago may form perfectly hemispherical cushions more than half a metre in diameter (Fig. 110), while A. simplex of Central Otago forms somewhat smaller cushions. Both species have thick, rigid leaves coloured bright orange-yellow.
The two flowering plants of fellfield which hold the altitude record are Hebe haastii and Parahebe birleyii, both having been recorded at 2900 m in the Mt. Cook region.144 At 2800 m Ranunculus grahamii is not far behind. Above these altitudes only lichens and mosses cling to steep rocky faces in the zone of permanent snow.
Screes or shingle slips might be regarded as a very special type of fellfield. They are widespread on the drier eastern mountains of Canterbury and Marlborough and some mountain peaks may have their mid and lower slopes completely buried in deep aprons of angular stones through several thousand metres of altitude (Fig. 111). These vast accumulations result from the already mentioned rapid disintegration of greywacke under high alpine conditions, and the relatively slow downward movement of the rock fragments in the absence of heavy rainfall.
Figure 111 A steep scree on the Craigieburn Range, Canterbury. The forest is of mountain beech (Nothofagus solandri var. cliffortioides).
Photo: J. W. Dawson.
The best known scree species is the penwiper plant (Notothlaspi rosulatum) (Fig. 112), which belongs to the cabbage family (Cruciferae). Its rosettes of grey, fleshy leaves closely overlap in a dome-like arrangement, which reminded early settlers of the similarly arranged and sewn together diamonds of felt on which they wiped their quill pens. The quite large flowers in massed heads are ivory in colour and have a very strong perfume reminiscent of stock in the same family.
Other notable plants restricted to mobile screes are Ranunculus haastii with large yellow flowers, Wahlenbergia cartilaginea, and Lobelia roughii, which has distinctive elk's-horn-like leaves with red teeth. Stellaria roughii in the chickweed genus is also common, as are two species of Leptinella of which L. atrata, with its almost black flowers, is the most remarkable.
The scree endemics die down in winter and most are perennials. The sole exception is the penwiper, which flowers in its second year then dies.
A number of species common on the more stable parts of screes particularly near the margins are also to be found in ordinary fellfield. Among these are Epilobium rubromarginatum, Poa buchananii (a grass) and patches of Acaena glabra. Acaena glabra belongs to the bidi-bid genus, but its seeds do not have the tiresome habit of attaching themselves to clothing or the wool of sheep, as do those of its more common lowland relatives. The seeds of Acaena glabra have spines but these lack hook-like recurved hairs at their tips. Perhaps the most unusual species in this group is Craspedia incana, a ghost-like plant with all its parts densely clothed in long, white, woolly hairs.
At higher altitudes in sheltered hollows, such as cirques or smaller depressions, snow will persist well into the growing season. Plants growing in such sites must be able to reproduce in just a few months, but they have certain advantages over the plants of the surrounding fellfield. They have more shelter from gales and, with reduced erosion on their concave slopes, a deeper soil which has a steady if cold supply of water from the gradually melting snow. The flowers of some of the snow bank plants may actually open beneath the melting snow. This is the case for two species of Caltha with their Ranunculus-like flowers, those of C. obtusa being white and C. novae-zelandiae yellow. Snowbank plants form a continuous sward, with the snow patch grass, Chionochloa oreophila, usually page 192predominating. Among other prominent plants are Ranunculus sericophyllus with deeply divided leaves and relatively large yellow flowers; Celmisia allanii, with patch forming rosettes of fluffy pale grey to snow white leaves; the related but pale green C. haastii, and two mat forming species, which although flowering plants look remarkably like mosses — Raoulia subulata and Drapetes lyallii.
In this type of vegetation small cushion plants are characteristic, with Dracophyllum muscoides the most common, but also the silvery Raoulia hectorii, Anisotome imbricata (Umbelliferae) with dense silver-grey hairs (Fig. 114) and Phyllachne rubra. Small rosette herbs grow in and between the cushions including Anisotome lanuginosa (also with dense matted silver-grey hairs obscuring the leaves) and the small spaniard Aciphylla hectorii. A few small grasses, sedges and luzulas of the rush family may also be present, and small grey lichens are often an important component.
As a result of freeze/thaw action the surface of the cushion moorland is often shaped on level areas into a very regular pattern of hummocks and hollows, which tend to elongate into alternating ridges and trenches on slopes.