Cool climate grevilleas do well here

Press, 28 February 1986, Page 8

Cool climate grevilleas do well here

Gardener’s DIARY

j Derrick Rooney

Half , a day’s work digging and forking through a patch of soil to remove the traces of a vigorous but shy-flowering day-lily has finally given me a space for a most attractive Australian shrub that I decided some time ago should be in my garden. It is Cfrevillea Black Range, a winter-flowering bright red form of Grevillea lavandulacea (the ordinary form has rosy pink flowers) collected in the wild by an Australian nurseryman about 25 years ago and propagated by cuttings.

A number of other forms of this grevlllea, grown in Australia, are not generally available in New Zealand. This is unfortunate, because this is one of the hardier and more compact grevilleas suitable for growing in the eastern South Island, where species from the cooler regions of Australia grow very well in our relatively generous rainfall and dry atmosphere. Grevilleas, members of the Protea family, come from all parts of Australia and Australian horticulturists divide them into three groups — spiderflowered types, tooth-brush-flowered types, and those with brush-like flowers. This arbitrary pigeonholing doesn’t necessarily reflect the botanical relationships between the species, but it is convenient.

From a New Zealand gardener’s point of view the least useful are the brush-flowered types, because while these include some of the most spectacular varieties, they are of tropical origin and of little use as outdoor plants in most gardens here. In general, the spiderflowered types (Black Range is one) originated

in the cooler districts and are vigorous and fairly hardy here. Typical examples of this group are the old warhorses Grevillea juniperina and G. rosmarinifolia, which were among the first Australian plants cultivated in Britain.

The toothbrush types are in general less hardy, but the group does include some real toughies which grow up to the highest altitudes for shrubs in Australia.

Many of this group have deeply lobed or sawtoothed leaves; two hardy species are Grevillea acanthifolia and G. asplenifolia, which when hybridised at Poorinda in Victoria by the late Leo Hodge produced a wonderful hardy shrub called Poorinda Peter.

Grevillea gaudichaudi Is another in the toothbrush group which has come Into prominence recently. A spreading, prostrate plant, it has been pro-

and Poorinda Royal Mantle are what plant breeders call F. hybrids —• the first generation offspring resulting from a cross between two wild species. They have hybrid vigour. On the other hand wild hybrids such as G. gaudichaudi, which originated in areas where two or more related species overlap and have created “hybrid swarms,” may be the result of many generations of interbreeding. One might say the hybrid vigour has been bred out of them! Still, Grevillea gaudichaudi is, I think, the more attractive plant of the two if you can get it to grow well.

selections from wild species have been named by Australian propagators. No-one in New Zealand could possibly know or grow all of these, and the best I can do is mention a few that I have seen growing well in Canterbury.

If you want a vigorous, hardy shrub which will grow very quickly and flower throughout the summer, you can’t really go past Poorinda Peter. For winter flowering, I’d give Red Cloud pride of place, even though I don’t grow it. This is a dense, compact, silverleaved shrub with bright red flowers, raised by crossing G. lavandulacea with the woolly-leaved G. lanigera. Both these species are important in horticulture, the former having provided such - selections as Black Range and the latter a praiseworthy cultivar in Astra.

two factors would have been fatal on its own, but the combination was disastrous — another lesson learned!

Where they rested on the straw the twigs and leaves of Grevlllea lanigera just rotted away. Since then I’ve noticed that in my garden the grevilleas (large as well aa small) dislike being mulched with straw, even in very open sunny positions, whereas they have ho Objection to being surrounded with well-rotted sawdust.

The' fact that they like acid soil may have some bearing on this. Never spread lime near grevilleas —they hate it. As for superphosphate, don’t even think about it Super near grevilleas is a no-no. Even a light dose can be severely detrimental, especially for the toothbrush types, which are so efficient at extracting phosphorous from soils where it occurs naturally at very low levels that a dose of super can hit them the way uncut heroin hits a junky.

Animal manure doesn’t hurt them, but it doesn’t do much good, either, so if you have dung to be flung around the garden you may as well save it for the roses and raspberries, on which it will confer tangible benefits. To get back to Astra: this has the same low, spreading habit and good foliage as the ordinary species, but its flowers are bigger and brighter.

I think it’s a shrub with a lot of quality, and I’ve just put one in to soften a couple .of rocks that I “planted” at an awkward bend in a path where a succession ' of r choice plants has been ruined by trampling feet or trailing hoses. r