New Zealand buttercups are renowned for the large sizes of some of their flowers and leaves. The delicate white or cream flowers, two or three inches across, of the Mt. Cook lily, R. lyallii, are a feature of some alpine vegetation throughout the Southern Alps. This species is one of over 40 occurring in New Zealand. The genus itself is a large one, containing over 300 species distributed throughout the world. Several of the European buttercups have been introduced to this country, and of these some have become serious weeds in damp pastures. Of the native species, four are found in Australia and Tasmania and one in Chile.
The alpine vegetation is the most common habitat for the native buttercups, especially the large-flowered ones. R. lyallii sends up saucer-like leaves, up to 9 in. across, from a thick root-stock. The beautiful flowers are borne on stout stalks a foot or more in height in late November, December, and January. R. godleyanus, from near the source of the Rakaia River southwards, with its yellow flowers, is nearly as attractive. R. nivicolus on Mount Egmont, with its golden-yellow flowers, is one of the striking features of that mountain. There are many other large-flowered mountain buttercups. Some are finding their way into cultivation and are being successfully hybridised. Natural hybrids between some species are also plentiful in the field.
Many smaller buttercups are also found in the mountains, and others are common in damp places in forest and throughout the lowlands. R. hirtus is probably the commonest and most widespread of these. It occurs in many forms, and is a hairy plant with three-foliate leaves and small flowers. Each leaflet is broadly ovate. Another very common species, found mainly in grassland and herbfield from sea-level to subalpine altitudes, is R. lappaceus. It also has many forms and is one of the species that extends to Tasmania and Australia.
R. chordorhizos, R. crithmifolius, and R. haastii are three buttercups belonging to that unique group of plants occurring on mountain screes. R. paucifolius is one of the rarest plants in the country. It has been found only on limestone rocks at Castle Hill, Waimakariri River.
by Alec Lindsay Poole, M.SC., B.FOR.SC., F.R.S.N.Z., Director-General of Forests, Wellington.