Banksia rewards effort

Press, 5 October 1984, Page 15

Banksia rewards effort

GARDENING

by

M.Lusty

Banksia coccinea has always been one of the more difficult species of the genus to establish. However, a number of individuals have been succcessful and undoubtedly pleased with their endeavours because this is a most attractive plant to grow. It is a variable endemic

from Australia, with reddish orange inflorescence appearing predominently in the spring. The flowers are rather squat, the leaves stubby, and in its natural habitat of the southern coastal region of Western Australia it varies in size from a shrub to a small tree.

Just how it will ultimately

conform here remains to be seen, but much will depend on locality and the treatment given. Judicious pruning after flowering is definately beneficial, if only to make the plant even more floriferous.

This plant is now stocked by some of the Christchurch nurseries.

The enclosed twig shows severe browning of its foliage. This appears to have started on the inside of the shrub and is gradually destroying the outer parts as well. Would you advise on the cause and treatment? R. R. (Belfast).

Juniperus sqamata “Meyeri” is unfortunately one of the most susceptible of all conifers to caterpillar damage. Regular spraying with an insecticide, such as acephate, should keep matters under control.

My daphne bush has flowered well this year, but it has thrown out some very odd looking flower heads at the same time. The stems are quite thick and rather flattened zWhen compared to the normal ones, as enclosed. Could you comment, please? N. S. (Chch). The aberrations noted on this daphne bush are the result of fasciated growth. Development of this nature is not uncommon on these plants, it can also occur on various others. Fasciation, the cause of which is not known, results in normally cylindrical structures, such as stems, to become flattened.

The enclosed sample is from a pine type of tree which is giving cause for concern. It is one of several, all quite young and all showing almost identical loss of leaves. What hope is there of saving them? “Shelter Belt,” (Chch R.D.). The trees, Picea silchensis, shows evidence of a severe attack by the spruce aphid. There were also a few scale insects present on the samples, but the damage has been predominantly caused by the aphids. This aphid is specific. A drenching cover spray with all seasons or summer oil is recommended. The trees should be regularly inspected and spraying repeated as soon as the pest become evident again.

Enclosed are some of the few remaining leaves from a four-year-old oleander. It has made no growth at all, and those leaves which it had, and still has, are all discoloured. I have recently moved it to a sunnier spot in a large pot. Can you suggest anything further to do which may save it? H. H. (Chch). While it has not been possible to diagnose the cause of the browning of the leaves,

Gardeners’ queries

their very small size and insipid colour, plus the fact that the plant is kept growing in a pot, suggests it may be suffering from starvation. If this nerium has been retained within the same sized pot for the duration of its four years then it is most likely to have become root bound, and will have exhausted the soil in which it is, or has been, growing. Fresh soil and potting up may be the remedy to this problem. Any information on the cause(s) for the striping of the leaves of these irises, and the spotting of the others would be appreciated. The flowering of those with the yellowish striping does not seem to be as strong in colour or the flowers as large as in previous years, but this may be fantasy. L. D. (Chch).

The yellowish streaking prominent on the leaves of these irises is caused by iris mosaic, a virus infection transmitted by aphids and then crried by the bulbs. This disease is fairly common on some types of irises and where infection is severe shorter flower stems occur and progressively fewer flowers can result; there is no cure. Symptoms are likely to be more prominent where plants have to contend with other problems, such as poor growing conditions. The spots have been caused by a leaf spot fungus which affects all irises. Control can become more difficult as the disease becomes firmly established. The application of Bordeaux mixture, zineb, or maneb, from early growth should be maintained. Good aeration, weed control, and the prompt removal of old or badly infected leaves is also advised. A query relating to failure of bulbs to flower has unfortunately been mislaid. If the Christchurch writer would care to resubmit the problem it will (hopefully) be answered as soon as possible.

Gardeners’ Queries should be sent directly to Mr M. Lusty, 56 Wayside Avenue, Christchurch 5. Samples should be separately wrapped in a plastic bag with air holes. Provide representative, goodsized samples, and your name and address. A nom-de-plume can be used for publication.