Pottering around the rock garden

Press, 17 June 1988, Page 10

Pottering around the rock garden

Oardener’s I W DIARY I

Derrick Rooney

Last week, just before I ran out of space, I mentioned that over the last couple of months I had been making numerous changes in the garden, remaking some areas, scrapping some plants and adding some. Over the next few weeks I will write about

some of these? changes and my reasons for them. The rock garden seems as good a place to start as any. To maintain an extensive rock garden is aesthetically rewarding but leaves little time for other activities, especially in the main growing period, when constant tending and weeding are called for. Later, after midsummer, when the weather is hot and dry, precious “little ’uns” outdoors need much fussing when I would rather be fishing. So I am gradually mov-

ing all the precious little plants into large pots in the shadehouse or into troughs, where they are more congenially sited and easier to manage. It takes only one mistake, e.g. planting the wrong thing, to wipe out several treasures. One of my mistakes was Potentilla anserinoides. This attractive low, creeping plant has the distinction of being one of the few indigenous members nf the rnce familv The species probably is found only in New Zealand, but it has close relatives elsewhere. One of the Canterbury populations is on the shores of Lake Selfe. With its fugacious but bright yellow flowers and ferny brownish leaves this plant makes very attractive summer groundcover (it disappears underground in winter) when suitably placed. My mistake was to plant it in the rock garden instead of underneath rhododendrons or in some other place where it could just look pretty and do not harm, like a bathingbeauty competitor. What

happened was that it pottered quietly away for several years then suddenly erupted, overrunning everything in its path like a flow of lava. A second mistake compounded the problem: I introduced to the rock garden a pretty little pink violet, found in an old homestead garden. It was either Viola sylvestris or a form of V. riviniana, which, I later learned, is ranked among the naturalised weeds. It, too, behaved with perfect decorum for several years, then suddenly revealed itself as a latent thug. Its offspring appeared everywhere, their roots seemed to go down to China, and every broken piece left in the ground seemed capable of sprouting again into an even bigger plant. As time and weather

permit I am clearing, as best I can, boles in this carpet of thugs and filling them with tough plants (mostly small shrubs) that should be able to hold their ground. One plant whicir has been there for years and has successfully, so far, repelled boarders from its root zone is an indigenous subalpine shrub (actually a conifer, although ' it doesn’t look like one). It belongs to the celery-pine family and grows very

slowly — so slowly that some of the huge old specimens to be seen in the mountains must have achieved extreme age. Its name, according to the latest botanical revisions of the New Zealand conifers, is Phyllocladus aspleniifolius var. alpinus, but it is better known as just plain P. alpinus. Some forms of this shrub have green “leaves” and some are glaucous; often the two grow side by side in the wild, but gen-

erally the glaucous forms predominate at higher altitudes. In Canterbury greenleaved mountain celery pines grown down into the higher beech forest, where They may be small trees; this happens in Westland, too. The glaucous forms always seem to remain shrubby and this, plus their snail’s-pace growth, suits them to rock-garden use. The glaucous, or blue, colouring is not genetically stable; glaucous plants may produce green offspring, and vice versa. The form that I have, known to some gardeners as “Cockayne’s Blue,” came originally, I believe, from somewhere near Temple Basin; whether it was selected by the great botanist is uncertain. It is not mentioned in his book on the cultivation of native plants. It has always seemed curious to me that this plant has never been widely circulated among rock gardeners. Its growth rate (4-scm annually) is just about perfect for rock gardens and it can be propogated (admittedly with some difficulty) from cuttings.

Behaved with perfect decorum for several years

Glaucous forms always seem to remain shrubby