Plant collecting can cause problems

Press, 20 July 1984, Page 10

Plant collecting can cause problems

Gardener’s W DIARY

Derrick Rooney

The advantages of a wintry spell, such as we experienced last week-end and a coincident and persistent bout of flu are few, but they exist. One of them is that the combination is highly palliative of the conscience. For a few days it is possible, free of guilt, to relax by the fire and dream summer dreams. Never mind the untrimmed hedges, the unpruhed vines, the accumulation of homeless plants overflowing from the terrace on to the path. The trouble is that when the day dream is over, the flu has gone, and the sun is shining again the hedges still have to be trimmed, the vines remain to be pruned, and the plants must sooner or later be planted. In some ways this is the worst problem of all. All gardeners whose enthusiasm sometimes overcomes their common sense know it well, This plant, that plant — they had to be acquired because, well, because they were rare, they looked interesting, or just because they were there. The resultant pile-up usually includes some of the most interesting Slants — and these are just le ones which cause you to wander round the garden for hours, wondering where to put them. A shining example is Chamaedaphne calyculata nana, a handful of a name which disguises a charming little North American shrub. Despite the name it is not a special new kind of daphne but a member of the erica family, related to our own native snowberries. In its wild state on the North American equivalent of moorlands it makes dense, low thickets in peatbogs. The leaves are small, leathery, brownish green and not those of the

New Zealand snowberries. Small pure white, lanternshaped flowers appear at the branch tips in early spring. Chamaedaphne does not, according to American references, require bog conditions in the garden but one imagines it would need a cool spot well sheltered from noriwesters. I shall treat it accordingly, if I can find such a spot. Propagation is by cuttings, taken in late summer. Seed, says my reference book, germinates well, but grows very slowly. It doesn’t say how slowly is “very slowly” but I doubt whether the chamaedaphne could match the snail’s pace of another little North American shrub, Petrophytum hendersonii, which of all the shrubs I have grown takes the booby prize for reluctance. I see by my label on the specimen in my shadehouse that it grew from seed which I sowed in August, 1981. At this writing it is all of 4cm across and almost 2cm high, and if it continues at that speed we may have a National Government again by the time it is ready to plant out. Seedlings of another species, Petrophytum caespitosum, are proceeding at similar pace. An interesting aspect of these little shrubs, which in nature are plants of the high screes of the mountains in the Pacific north-west, is that they belong to the rose family. At one time they were included in the Spiraea genus and, like the herbaceous members of this family, they have pretty little bottlebrush flowers. I don’t expect to see any for quite a few years, unless their growth rate increases with age. Three species of petrophytum are known indent-

ally, all native to the Pacific north-west, and while the taxonomists have them all sorted out there are very few horticultural diffences between them. About the only way of telling my two apart is that Petrophytum caespitosum has only one visible nerve on its leaves, whereas P. hendersonii has three.

Phlox is another prominent genus in North American rock gardens, but with the exception of a few subulata types which provide sheets of bright colour in late spring few phloxes are seen in New Zealand gardens. So I welcomed a newcomer this year, “Daniel’s Cushion.”

The name suggests a hybrid origin, perhaps with the delightful, but difficult Phlox caespitosa as one ! jarent, and the flower size I haven’t seen the flowers yet but the catalogue describes them as “very large”) indicates some involvement of P. nivalis, the species responsible for the popular “Camla” and “Betty.”

The uniformity of plants in the nursery suggested that the growth habit of “Daniel’s Cushion" will be dense and bushy — a . plus factor. And it does not ration its colour to flowering time — in early winter it looked quite spectacular because the old leaves turned to glowing flame colours (since then they have died off and turned

drab brown but are still hanging to the plant, a less attractive feature but one which I can tolerate in the dead of winter).

Despite the dead leaves, the. plant looks healthy, which is encouraging because dieback in winter has been a problem in my garden with a number of the cushion-type phloxes. Sometimes in spring there are barrowloads of dead material to be composted, though I have not yet lost an entire plant. The cause of this dieback is a mystery. It doesn’t appear to be disease and frost damage is doubtful, because in North America these plants tolerate much lower temperatures than they would ever experience here.

The answer may be that in our milder climate the sap keeps flowing year round, so that when frosty spells do occur the plants are in a very vulnerable state."

Luetkia pectinata is another newcomer from the Pacific north-west I had seed of this last year but it came to nothing, and cuttings a year or two ago failed, though the friend who sent them grows the plant very well in a fairly dry garden. Now, however, I have- a strong-looking well-rooted plant from a commercial source.

Like the Petrophytums, Luetkia pectinata belongs to the rose family but when it is out of flower the most experienced gardener could be excused for believing it to be a saxifraga.

In summer Luetkia pectinata has short spikes of pale yellow flowers. A cool, moist spot in the rock garden, facing south, should provide a congenial home for it.