Some hebes successfully domesticated close to home

Press, 1 July 1983, Page 8

Some hebes successfully domesticated close to home

«ARDENER’S W DIARY

Derrick Rooney

Last week I wrote about some of the hybridising that has been done in Britain with species of New Zealand hebe.

Much closer to home — in Banks Peninsula and North Canterbury — there are three closely related and most unusual species of hebe which are too tender for most gardeners in Britain, but which have provided, separately and together, some excellent plants for Canterbury gardens.

These are Hebes hulkeana, raoulii, and lavaudiana — a distinctive and exclusive section of the genus, so different from most of the other hebes that they might well deserve a name of their own. All three are shrubs of modest dimensions, and each of them has forms small enough for the rock garden. All have thick, fleshy, glossy leaves, frequently with red margins. Unlike most other hebes, which have flowers in short, dense spikes among the leaves they have sprays of flowers carried well clear of the branches, after the manner of a lilac. The resemblance is closest in Hebe hulkeana, which mimics the lilac in colour also, and is popularly known as the “New Zealand lilac.”

My favourite for the rock garden is Hebe raoulii, in its better forms, even though these are a little trickier to propagate and transplant than most other hebes. Like the other two, H. raoulii is confined to the dry north-east of the South Island, but it comes much further south (almost to the Rakaia River) than either of the others, and ranges up into Marlborough. Three geographic variations of Hebe raoulii are listed. Within each variety, there is a range of plant forms from straggly and horticulturally useless to compact and floristically delightful. The common Canterbury form is the variety of raoulii, a low-growing, manybranched shrub, sometimes sparsely leafed in the wild; the leaves are rimmed with red, and shaped like little tapering spatulas with teeth.

The easiest place to see it handy to Christchurch is on the rock outcrops at and near Porters Pass.

Seed is probably the best way to propagate it. Cuttings will root, though slowly, but established plants do not transplant readily. The good forms seem to come fairly true from seed — I have several compactgrowing plants in my rock garden, and they seed themselves around, producing babies which are little duplicates of the parents. In contrast, hebe from other groups are highly immoral — they crossbreed almost recklessly, and produce many worthless offspring. The distribution of Hebe raoulii var. raoulii is now effectively confined to rocky places in the diy foothills, though there is evidence that it once ranged more widely. The “type locality” — the place of origin of the speci-

men on which the description of the variety is based — is Akaroa. But no Hebe raoulii has been found growing naturally on Banks Peninsula since the mid-1860s, when Armstrong found a specimen at Purau. A choice little shrub for the rock garden is the variety maccaskillii, which grows on limestone outcrops in the Weka Pass area. This is the smallest and neatest of the variations of Hebe raoulii, and is one of the best native shrubs for the rock garden. Established plants produce numerous sprays of cool pink flowers. In spite of its wild habitat, Hebe raoulii var. maccaskillii does not need limy soil in the garden. It is best propagated by seed, though small cuttings will root. The third variety of this species, pentasepala, is a Marlborough plant; its type locality is listed as Goose,berry Gully, Molesworth. This is a bigger and generally more robust plant than either of the others, but its open growth and sometimes gawky habits render it less horticulturally desirable.

Marlborough is also the main stomping ground of Hebe hulkeana, one of the most famous New Zealand plants, and one of the first to be grown in the conservatories of wealthy nine-teenth-century English gardeners.

Alas, the best and most spectacularly flowering forms are coastal ones — a particularly good selection goes under the name “Sea Spray” — and these ae either doubtfully hardy or downright tender in inland gardens.

Inland forms from Marlborough and North Canterbury are, however, hardier; the species reaches its altitudinal limit about 500 metres and it should thus be possible to select plants hardy enough to grow in most New Zealand gardens. The hardiest I have grown is a white-flowered form which came, I was told, from the upper Awatere Valley. Some good forms with deep lilac flowers used to grow near the Inland Kaikoura Road at the Conway River gorge. Most of these, however, have been destroyed by aerial weedspraying. In cultivation H. hulkeana has been hybridised with its two cousins, and absorbed a dash of extra hardiness from them, to create two first-rate garden shrubs. These are “Hagley Park” (also known as "Hagleyi,” “Hagleyensis,” and “Lady Hagley”) and “Fairfieldensis” (also known as “Fairfieldii”). The former was among a batch of seedlings raised at the Christchurch Botanic Gardens in the 1940 s by Walter Brockie. It was shown by subsequent controlled/hybridising to be a cross u.tween H. hulkeana

and H. raoulii, the former being the seed parent.

It has inherited the floristic elegance of hulkeana and the tidier leafage and small size of raoulii, and is compact enough to be grown in the rock garden. Small cuttings, taken in autumn, root easily, and sometimes flower in their first year, so free-flowering is this little shrub.

The blooming period extends over several weeks in early summer and the flowers, which are purple, are held well clear of the foliage in conical sprays. Plants similar to “Hagley Park” have been reported occasionally from the wild where populations of the two species overlap. But “Fairfieldensis” could not occur as a wild plant, and its origin is a minor horticultural mystery. The parents are Hh. hulkeana and lavaudiana, which do not meet as wild plants, though of course they are sometimes grown side by side in gardens. A nursery at Fairfield, near Dunedin, was the first to distribute this plant, I believe in the 19205, and it may well have arisen as a spontaneous hybrid on the premises.

“Fairfieldensis” is very distinctive, with almost round leaves, deeply toothed and red edged. The flowers are violet, in dense sprays. Nurseries often sell it under the name “Hebe hulkeana,” but no-one who had ever seen the parent growing wild could confuse the two.

If it has a fault this is an inclination to straggliness as it ages, if left untended. An annual light trim after flowering keeps it neat and compact, and I think also helps to prolong its life — when well tended, “Fairfieldensis” is the longest-lived shrub in the group. It is very free flowering, which is more than can be said of its other parent, H. lavaudiana. This is a Banks Peninsula plant. While there is evidence that it might have grown in riverbeds and gorges elsewhere in Canterbury in time past, it does not grow anywhere else now but the peninsula, where it is more-or-less confined to rock outcrops near the summits, often south facing. It is closer in appearance to h. hulkeana than to H. raoulii, but unlike hulkeana it will not thrive in a hot northerly aspect in the garden.

My experience with it has been that it is less tolerant of summer drought than the other two, but must have sharp drainage around its neck to prevent stem rot. It also needs good circulation of air all around its foliage to minimise septoria spot, a bacterial disease which can be troublesome, sometimes fatal, in many hebes. Many forms of Hebe lavaudiana are shy flowers. I have had two plants in my garden for some years without a flower.

Last summer, however, I collected seed from a group of very free-flowering plants in the wild. I hope this will provide me with some which are less recalcitrant.

When the flowers are produced they are very pretty, pale lilSc quickly fading • almost to white.