The alpine flora of New Zealand is vastly different from that of the lowland areas, and also vastly different from the mountain flora of other countries. Alpine plants are fascinating for the variety of their leaf forms and for the clear colour of their flowers, though in New Zealand their colour is usually white, cream, or yellow, the flowers being produced in great profusion. An alpine meadow in January is a beautiful sight with masses of large white cups of Ranunculus lyallii and the large daisy-like flowers of Celmisias. Both North and South Islands are mountainous, the latter extremely so, with the Southern Alps running almost its entire length. The snow line is the main factor determining the distribution of mountain plants and this varies greatly according to aspect and climatic conditions. At an average of 5,000 ft altitude a new type of vegetation appears, together with an abundance of certain plants seldom seen at lower levels. There are about 500 species of flowering plants found only in the mountains; with others, the total of mountain species is about 950.
The lowland rain forest is gradually replaced by shorter trees which become more and more stunted in growth and these give place to subalpine scrub. Shrubs of divaricating growth-form and those with stiff spiny leaves form dense masses which are almost impenetrable. Above this region are tall tussocks, herb fields, and alpine plants. The latter are often very small, only a few inches high, with inconspicuous greyish leaves, but beautiful flowers, found growing in small valleys or in the shelter of rocks.
At different levels are representatives of the lower groups of plants; fungi (especially in Nothofagus forest), lichens, mosses, and liverworts, also lycopods and some ferns, as species of Asplenium on limestone screes.
The plants of mountain areas have certain characteristics which enable them to withstand extremes of climatic conditions. In sunshine the stony ground may become hot though the water beneath is icy cold; frosts may occur at all seasons of the year and perhaps last for several days, while periods of drought or of rain and mist, together with strong winds and the constant breaking of rocks on mountain screes, combine to produce an unstable habitat. So the plants found are those which can exist for a period without supplies of fresh water or which have very long root systems capable of penetrating far into the ground to reach water. Many have a mat or cushion form of growth able to withstand winds as well as frost and snow. The leaves may be tough and leathery or thick and fleshy (in which water is stored), and most of them have a dense covering of hairs on one or both surfaces, thereby checking the rate of transpiration. In that interesting group of Hebes known as the whipcords, the leaves are reduced to close-set scales on thin, hard stems. Many plants which grow erect in other situations are, in exposed habitats, prostrate shrubs, mats, or have rosette forms.
The plants of the mountain regions are mostly evergreen, whether they are tiny plants, or grow as mats or cushions, shrubs or stunted forest trees. This is true even of those which are covered in snow for half the year. One of the first impressions, during the flowering season, is of the profusion of flowers, and at the same time of the lack of colour. The flowers are nearly all white, and many of the leaves appear grey due to the thick covering of hairs. Even those plants which are found in other parts of the world with coloured flowers, in the New Zealand mountain areas have white flowers. Gentians elsewhere are known for their bright blue colours, but the 24 species here are white, or very faintly streaked with colour. Our forget-me-nots are pale or deep yellow, though in sub-Antarctic Islands the forget-me-nots are blue as are the gentians. In fact, blue flowers are very rare in New Zealand; the little orchid Thelymitra is blue but Wahlenbergia gracilis, the blue-bell, is usually a dingy white. A number of flowers are yellow such as Helichrysum coralloides and several species of Senecio which include some of our most beautiful shrubs. S. lautus is the most common, S. bellidioides is abundant in sub-alpine regions, S. lyallii with white or yellow flowers is common in alpine passes, while S. scorzonerioides, the snow groundsel, one of the most showy New Zealand plants, is found on wet herb fields. Some Hebes have tiny pale mauve flowers, and Cotula atrata, found on shingle slips, has flowers which are almost black. In contrast to the lack of colour in flowers are shrubs with brightly coloured berries (Coprosma, Myrsine, Gaultheria).
Among the plants of our mountains are many endemic species and most of these belong to only a few genera. The genus Celmisia, of which there are 58 endemic species, are the mountain daisies which have been regarded as the dominant plants of these regions. The flowers are white and usually large and beautiful. These are herbaceous plants, with leaves covered by hairs, and of shape and arrangements which seem to guard against loss of water by transpiration. In C. sessiflora, C. argentea, C. lateralis, and C. laricifolia are leaves of this nature. C. gracilenta is a species which is very widespread, being found throughout New Zealand from sea coast up to about 5,000 ft. C. spectabilis is also common and is recognised by a thick covering of buff-coloured hairs on under surfaces of leaves. Olearia is another genus with a large number of endemic species. These are shrubs or small trees with hard, leathery leaves having white or buff-coloured tomentum on the under surface. There are 32 species, all endemic. Olearia paniculata is found near the sea but also at great altitudes. O. moschata, mountain musk, is common in sub-alpine scrub as a tree 5 to 15 ft in height. O. ilicifolia is found throughout both Islands and O. avicenniaefolia is widespread at high altitudes.
The genus Hebe is a large one which is highly developed in New Zealand where 79 species are recorded, the largest number of any native genus. Most are endemic. They are found from sea coast to the upper limit of vegetation on our mountains. For many years this genus was known as Veronica, with the Maori name koromiko applied to many species. H. salicifolia is most widespread; H. traversii is common particularly on the Southern Alps, with H. monticola and H. epacridea in all mountain districts from Nelson southward to Otago. Many Hebes have minute scale-like leaves, overlapping and closely appressed to thin wiry stems. These are the whipcord hebes.
Aciphylla is another genus of which all the 39 species are endemic. Most of them have long thin spike leaves, forming a dense mass of fearsome appearance. The flower stalks are long, covered with spines, and bearing large panicles of flowers. When young the leaves are soft and may be eaten by cattle and sheep. Aciphylla monroi is found in alpine and sub-alpine regions. A. colensoi and A. squarrosa, kuri-kuri or wild Spaniard, are the best known and from the latter the Maoris obtained a scented gum.
We have some striking examples of the “cushion” habit of growth in the genera Raoulia and Haastia. When these plants grow to a large size the extensive mass with white hairy leaves has an unusual appearance which has given rise to the name “vegetable sheep”. Two species very common in the Southern Alps are Raoulia eximia and R. mammilaris, R. haastii is a much-branched prostrate herb of mountain river beds. There are 20 endemic species of Raoulia and the genus Haastia is also endemic.
The number of species found on North Island mountains is only about one-third of that found in the Southern Alps. The general pattern of mountain vegetation is found on Mt. Egmont where mixed rain forest gives place to shorter trees and shrubs; Libocedrus, mountains totara, hebes, shrubs of the daisy family, and tall tussock. Above are the alpine meadows and then the loose scoria in which few plants can maintain a footing. Lichens are prominent and some moss in boggy places. In the chain of the Ruahine-Tararua mountains there is the same general pattern and many of the same species are found.
That the type of soil is one of the most important factors in plant association is shown in the volcanic region, as in the Dun Mountain of Nelson. On the eastern slopes of Ruapehu there are extensive areas of scoria and at the base of the mountain much volcanic ash. These slopes have the same aspects as the nearby Kaimanawas, but instead of mixed rain forest, there is on Ruapehu a beech forest showing great variation in leaf form. The plant associations here are patchy, in places sheltered from sun and wind; Nothofagus fusca and N. cliffortioides are predominant. Under beech trees there is often a layer of fallen leaves up to 2 in. deep, in which little undergrowth survives.
The belt of shrubs above is dense and consists of Phyllocladus alpinus, species of Dacrydium, Coprosma, Olearia, Senecio, Hebe, and Nothopanax. Some of these, in upper limits, are prostrate or creeping. Smaller plants are Libertia pulchella, and some species of fern such as Hymenophyllum multifidum, Blechnum, and Polystichum spp. On the western slopes the belt of shrubs above the mixed forest is more like that of the Southern Alps. On Tongariro there are deep gullies, at altitudes of 4,000 to 5,000 ft where better soil has accumulated and growth is more dense. The dominant species is Phyllocladus alpinus with species of Dracophyllum, Nothopanax, Olearia, Coprosma, also Leptospermum scoparium and Gleichinia cunninghamii.
In some cases bogs occur only in certain seasons, and here Luzula colensoi is seen of very much greater size than in its usual habitat of dry scoria. Sphagnum moss occurs in bogs and may become the bed for germination of seed of manuka. Arundo conspicua, Drosera spathula (a carnivorous plant), and species of Carex may be found. As the streams are swift and icy, few algae are found. Close to the banks are Ranunculus rivularia, Celmisias, Juncus, and Epilobium. In hot springs at Ketetahi there are some blue-green algae and the fern, Hystiopteris incisa. On the pumice-covered plateau in the centre of the North Island and on the lower slopes of the three volcanoes, Ruapehu (9,175 ft), Ngauruhoe (7,515 ft) and Tongariro (6,458 ft), there is scrub formation, mainly of manuka (Leptospermum scoparium), with the attractive small shrub Gaultheria oppositifolia (snowberry), as well as G. colensoi and G. paniculata. There are eight species of Gaultheria, all endemic. G. rupestris is widespread in both Islands, and G. subcorymbosa and G. crassa are found on the Ruahine and Tararua Ranges and in the mountains of Nelson. These little shrubs have a profusion of small flowers, but the berries are larger and more showy. In this region is Dracophyllum subulatum, one of the grass trees, which lives on the poor soil of the volcanic plateau, on the Rangitaiki Plains, and in the Ruahine Range. D. stricta and D. recurvum are found in similar localities in the centre of the North Island sub-alpine regions. Other species of the genus are found in South Island sub-alpine regions, or in lowland areas.
Two species of Ranunculus, R. nivicolus, a slender erect herb, and R. carsei, a prostrate hairy shrub, also R. ignis, are found on the three mountains of the central plateau, and also on Mt. Egmont. The willow herbs, species of Epilobium, E. pernitens, E. perplexum, and E. cockaynianum, may be found in pockets of earth on the Ruahine and Tararua Ranges and on Mt. Egmont. The little eyebrights, Euphrasia monroi, and E. tricolor on Ruapehu, Tongariro, and Egmont are partly parasitic in habit. On the scoria slopes of these mountains there is very little vegetation, but several species of Parahebe, P. spathulata with a root of great length and small, succulent, hairy leaves, and P. hookeriana, a much-branched, woody prostrate shrub, do survive. On Mt. Egmont are masses of alpine foxglove Ourisia macrophylla, which is also common on the volcanic plateau and Ruahines, where O. colensoi, O. caespitosa, and O. vulcanica are also found. Another common plant is Celmisia glandulosa, also C. spectabilis in patches of damp ground. C. incana and C. hieracifolia, with Astelia montana, form a conspicuous part of the vegetation of the Ruahine and Tararua Ranges, while the edelweiss, Leucogenes leontopodium, grows in large masses in alpine regions from the centre of the North Island to Canterbury, but the other species, L. grandiceps, is in South Island only. Of the Olearias, O. nummularifolia and O. ilicifolia are widely distributed mountain species. Senecios are very common subalpine plants. The shrubby groundsels, S. eleagnifolius and S. adamsii, are found in the Tararua and Ruahine Ranges but most species occur only in the South Island.
Similar plant covering was found on the slopes of Mt. Tarawera before the eruption of 1886 when large areas were covered by volcanic ash, in some places to a great depth. Where the covering of ashes was but a thin one, the vegetation reappeared in almost its original form, but in other areas there were great changes. Following the eruption very heavy rain caused changes in the land, so that many gullies were formed in the loose soil. Here some new species became established from seed brought by birds or blown by the wind. Masses of toetoe, Arundo conspicua, are now seen, with much tutu, Coraria sarmentosa and cushion plants of Raoulia australis. Some plants described by early botanists have not been found since the eruption: such is the case of Utricularia mairii, one of the unusual bladderworts, found floating in Lake Rotomahana and described in 1872 by T. Kirk and G. Mair.
Although the flora of the Southern Alps is much better known than that of any other parts of the South Island some differences are seen in northern areas on the Dun Mountain in Nelson and the Kaikoura Ranges.
The Dun Mountain is part of the “Mineral Belt”, the rocks of which are peridotite and serpentine. A luxuriant forest of southern beech suddenly ceases on the serpentine and is replaced by tall tussock grassland and short, stunted trees. That there are differences in the soil is shown by the growth of trees such as the broadleaf (Griselinia littoralis) and southern beech (Nothofagus fusca). The ground is stony and vegetation is sparse. Cassinia vauvilliersii (mountain cottonwood); the tangled woody branches of Hymenanthera dentata; a grass tree, Dracophyllum rosmarinifolium; all appear to be able to live in these dry conditions. Of smaller plants are the prostrate shrubby Pimelia suteri, the yellow forget-me-not Myosotis monroi, and a rosette plant Nototholapsi australe, similar to the “penwiper” plant of the shingle slips.
In the Kaikoura Mountains three species of Heli-chrysum are common: H. microphyllum, H. selago, and H. coralloides. Geum uniflorum and G. avens are found in pockets of peaty soil among rocks. The yellow-flowered Ranunculus lobulatus is known as the “Kaikoura buttercup”. There are many parts of these mountains which have not been explored from a botanical point of view. On screes in these northern parts of the South Island is the dwarf succulent, with its dark leaves, Wahlenbergia cartilaginea, seldom found elsewhere; also Hebe epacridea, H. pinguifolia, and H. decumbens.
In the South Island ecological factors are much more apparent than in the north, and there is a marked difference between the vegetation growing on the eastern and western sides of the Southern Alps. On the former, the rocks in the main break easily, hence the many barren screes. It is probable that the eastern slopes may have been covered by forest, later destroyed by fires both by Maoris and early Europeans. Sheep and cattle have no doubt destroyed other vegetation. The alpine vegetation on the western side has changed but little. There is still the luxuriant rain forest, with the beech forest further south. The tree limit varies but in the Southern Alps the forest reaches to over 4,000 ft; above this are the snow tussocks and the herbfields. Flowering plants have been recorded at 9,000 ft, and in sheltered crevices have been found Hebe haastii, Celmisia discolor, and Ranunculus sericophyllus and, above Lake Hawea, Raoulia youngii. It is difficult to find these plants among the shifting stones at these great heights as the general colouring blends with that of their surroundings. Two plants of matted growth-form and tiny leaves are Donatia novae zealandiae, found where there is trickling water, and Phyllachne clavigera both growing in places where it would seem plants could not live. At lower levels are other species of Phyllachne, often covered with masses of snow-white flowers. Hectorella caespitosa is a perennial dwarf shrub of cushion habit found in high altitudes from Arthur's Pass southward, and of similar distribution is Parehebe birleyi, which grows on exposed crags at very great heights. Closely related to the Hebes is Pygmea, two species of which are found in high altitudes. P. pulvinaris forms very small, grey-green rounded cushions in the northern parts of the Southern Alps. It flowers as the snow retreats, at 4,500 ft in November, but later in the season at a much higher altitude. P. tetragona has a more open habit of matted woody branches and large flowers and is found on barren stony summits towards the south.
Among the shifting mass of stones on steep slopes it is amazing that plants manage to survive; these have long rhizomes penetrating to damp spots, and succulent leaves covered by hairs. The individual plants are widely scattered but it is interesting to note that of nine species recorded, each belongs not only to a separate genus but also to a distinct family, quite unrelated to the others, though most of the genera are represented by other species in the surrounding country. These species are: Stellaria roughii (Cary-ophyllaceae), Ranunculus haastii (Ranunculaceae), Anistome carnosula (Umbelliferae), Acaena glabra (Rosaceae), Notothalpsi rosulatum (Cruciferae), Cotula atrata (Compositae), Epilobium pycnostachyum (Ona-graceae), Lobelia roughii (Lobeliaceae), and Poa sclerophylla (Gramineae). There are other plants which grow on screes but are not confined to them, being found also between and on rocky crags. Among such plants are Craspedia incana, which appears as a white mass with yellow flowers, Myosotis traversii, Hebe epacridea, and Senecio glaucophyllus; species of Haastia grow at the edges of screes but their roots penetrate firmer substratum. Shingle gives place to more stable substratum, sometimes called a fell-field, where growth-forms are prostrate shrubs, cushion and rosette plants, semi-woody thick stemmed shrubs, and tussock grasses. Among such plants are several species of Celmisia – C. laricifolia, C. discolor, C. viscosa, C. sinclarii, C. haastii; some species of Dracophyllum, Hebe pinguifolia, and similar species of this large genus; broad green mats of Ourisia caespitosa; the creeping mountain foxglove; large cushions of Raoulia grandiflora; and the mountain totara, Podocarpus nivalis. On the western side of the Southern Alps and on mountains of the North Island a similar area with much more dense vegetation is known as a herbfield. There the conditions are better and there is a more plentiful supply of water; the plant covering is thicker and the growth more luxuriant. In addition to the foxglove, buttercup, and bog celmisia of the Egmont herbfields, and the alpine astelia and edelweiss of the Tararua-Ruahine mountains, the South Island herbfields have the beautiful Ranunculus lyallii, often acres of it which when in full bloom is a glorious sight. There are more species of Celmisia and Ourisia with showy flowers. Further to the south the species are slightly different but the main types still flourish.
Between the herb fields and the forest are belts of sub-alpine scrub which often becomes impenetrable owing to the interlacing branches of shrubs and stunted trees. There are great numbers of species found in various plant associations and these belong mainly to the genera: Hebe, Olearia, Senecio, Nothopanax, Dracophyllum, and Aciphylla, along with manuka, tussock grasses, bracken fern, and stunted beech trees. Cushion and matted forms of growth of Raoulia and Haastia, as well as of other plants, are common on slopes exposed to the wind.
On some mountain slopes are areas of bog. In these and in areas of peat, at edges of streams and similar places, are Donatia novae-zelandiae, Senecio lyallii, species of Ranunculus, Carex and Drosera, and cushions of Celmisia argentea. A very common plant in damp peaty soils, at moderate altitudes, is the Maori onion, Chrysobactron hookeri, which produces masses of yellow flowers. This, like the two Cassinias sometimes found in sub-alpine regions, C. leptophylla and C. vauvilliersii (cottonwoods or tauhinu), is not attractive to sheep which avoid also the wiry stems of Cyathodes spp., common among the tussock and providing a patch of colour when covered by white and red berries unusually large for the size of the flowers. In similar places are some of the smallest Coprosmas, C. petriei and C. pumila, forming mats which bear tiny, almost colourless, unisexual flowers but bright orange-red berries. On the edges of moraines and in river beds the willow-herb, Epilobium, is represented by E. microphyllum, E. tenuipes, E. erubescens, and E. melanocaulon. Here also are Muehlenbeckia axillaris, Discaria toumatou, Helichrysum microphyllum, H. selago, H. coralloides, Craspedia minor, and a few species of yellow-flowered forget-me-not (Myosotis). Cyathodes fasciculata mingimingi), C. fraseri, and C. empetrifolia are found in rocky places, together with Euphrasia monroi, E. revoluta, E. petrei, the profuse-flowering tiny Pimelia prostrata (New Zealand daphne), the large, very hardy, and more erect species, P. traversii, and P. aridula, particularly common in Marlborough and Otago.
Lacking the long backbone of the Southern Alps, the ecological factors in areas of Otago, Southland, Fiordland, and Stewart Island are somewhat different, resulting in different plant associations and in each of these areas are a few species confined to a particular locality. The genera with which we are familiar are represented in these southern parts by different species. For example, here are Ourisia macrocarpa, O. caespitosa, and O. gracilis (var.), and in Fiordland and Stewart Island is found O. sessilifolia.
In the dry alpine areas of North Otago are certain species seldom found elsewhere: Acaena buchananii, Hebe buchananii (with thick bluish-green leaves), Carmichaelia petriei, and two other unusual species of Carmichaelia. This is a barren-looking area as there is no forest, only a few trees in sheltered gullies, and large areas are covered by snow grass. Much damage has been done in these parts by rabbits. This area merges into Southland where localities with a southerly aspect receive some heavy rains. Most of this area was covered by forest, mainly of rimu, kamahi, and some southern rata (Metrosideros lucida), with tall tussock and some hebes. There are also extensive sphagnum bogs.
Cushions of Pygmea myosotoides, P. thomsonii, and P. tetragona are common. Celmisias in these southern areas are Celmisia hookerii, C. thomsonii, C. coriacea, and C. verbascifolia; while of Hebes those of southern distribution are H. laingii, H. haastii, and Parahebe canescens. These extend to Stewart Island. Species found only in South Otago are H. poppewellii, H. annulata, and Celmisia poppewellii. The South Otago area has many species in common with Fiordland such as Ranunculus buchananii, Aciphylla pinnatifida, Dracophyllum menziesii. In Fiordland there are extensive beech forests of Nothofagus fusca and N. menziesii, and two buttercups not found elsewhere, Ranunculus matthewsii and R. baughanii, also an abundance of R. buchananii. The genera Ourisia, Olearia, Celmisia, and Senecio are each represented by local species. Putaputaweta (Carpodetus serratus), and Olearia oporima, O. angustifolia, and O. avicenniaefolia are common about Bluff and Stewart Island. Though there is little ground rising above 3,000 ft in altitude, much of the vegetation of Stewart Island is of the high-mountain type, such as Celmisia argentea, Donatia novae zelandiae, and Senecio lyallii.
In the southern alpine areas snow lies long. Cold rain and gales and cloudy days are frequent and these conditions are reflected in the vegetation; plants which are high-mountain plants further north are here found at much lower levels. Many species are seen growing under a great variety of conditions, and so many variations of growth form are found that the classification and identification of species and varieties are difficult. But from the viewpoint of the New Zealand botanist, the flowers of the mountains are both a delight and a rewarding study.
by Olive Rita Croker, M.A., Botanist, Wellington.