This is the largest genus of New Zealand shrubs, containing almost 80 species, many of which hybridise. It is typically a New Zealand genus for there are only about 100 species known. Most of the native ones are endemic though two are found also in South America. Others occur in Australia and New Guinea. The genus was once joined with Veronica which contains many herbs with cosmopolitan distributions, especially some that have become weeds of agriculture. There are no veronicas in New Zealand other than introduced ones. The family to which Hebe belongs is the Scrophulariaceae or snapdragon family, a widespread one containing about 3,000 species.
Hebes vary in life-form from large leafy shrubs to matted plants with whipcord-like branches. In these the leaves are almost reduced to scales which are closely appressed to the stems. The leaves are always opposite and usually entire. The flowers are smallish, mostly white or white tinted with lilac, borne in simple spikes or occasionally in large panicles. Hebes are found in all manner of habitats but are commonest in alpine shrubland, grassland, and fellfield. A number occur in coastal, lowland, and montane shrubland. A few only are inhabitants of forests. Some are confined to certain localities, while others are widespread. As most are propagated readily from cuttings and grow quickly, they are extensively used in horticulture both in New Zealand and overseas.
The widespread lowland species H. salicifolia, in the South and Stewart Islands, and its counterpart, H. stricta, and varieties in the North Island, are probably the best-known species. Both are much-branched shrubs, 6–10 ft in height bearing linear-lanceolate leaves 2–6 in. long. The Maoris used concoctions of these leaves for medicinal purposes. One of the best-known species in horticulture is H. speciosa which is the only one with deeply coloured flowers. These are reddish to violet purple. In nature it is confined to a few places around the North Island coast. It hybridises with remarkable ease, especially with the two above species, to produce a range of forms and flower colours. H. hulkeana is confined to rocky cliffs in Marlborough and North Canterbury but is also widely cultivated because of its large panicles of lavender flowers. It is one of the few tooth-leaved species. The higher altitude species often have smallish, elliptic leaves. H. odora is the best known of these and is a rounded, much-branched shrub about 4 ft tall. The so-called whipcord hebes are striking plants also much used in horticulture. There are over a dozen species of them found on the Volcanic Plateau and along the mountain chains. H. tetragona on the Volcanic Plateau and surrounding mountains is one of these. It is a dense shrub about 3 ft tall with squared branchlets on which the appressed leaves are less than one-twelfth of an inch long.
by Alec Lindsay Poole, M.SC., B.FOR.SC., F.R.S.N.Z., Director-General of Forests, Wellington.