Gardeners' queries

Press, 18 April 1980, Page 10

Gardeners' queries

Please find enclosed soma branches of my kowhai, which is 10 years old, has flowered beautifully for the last five years, and always looked healthy. Now it seems to be dying. I can't see any insect pest on it, including scales, but have still sprayed It with superior oil. Its leaves used to stay green until early spring but now they are all gradually dying. I have kept it pruned to form a shrub and it Is about eight feet tall. What could be the reason for this condition and is there any hope of saving it?—E.S. (Chch). There is no indication as to the nature of the disease which is attacking your kowhai; it tnay possibly be soil borne. If the problem originates from the soil then there is little that can be done. It is suggested that all diseased wood b e cut well back; any big cuts should be sealed and the tree be given an over-all application of bordeaux mixture. Further, it is suggested that you refrain from giving the plant its annual pruning this year. I have a wide concrete driveway and would like to plant something on each side of the beds which run along it. I would like it to cover the ground but not grow too high: and I do not wish to replant each year; the choice can be either flowering or nonflowering.—C.W. (Chch).

Unfortunately you have omitted to give the width of the beds and whether or not they are located in shade or sun. This makes it difficult to be as helpful as would otherwise be possible. For shady conditions Pachysandra terminalis and its less vigorous form “Variegata” is usafui. Various species and forms of Euonymus such as E. fortune! “Minimus” and “Silver Queen” will tolerate sun and shade, as ■will species of Cotoneaster such as C. congestus, C. oammeri, C. mlcrophyllus and C. adpressus. Conifers will also provide a good variety of form and colour as ground cover. Examples include Juniperus procumbens and J. communis depressa aurea (for sunny position), and Podocarpus nivalis. Other suggestions include Ericas and Callunas, Arctostaphyllos and soma of the smaller growing forms of Grevlllea. I am despairing for my bottlebrush, a good 10ft tall, once a splendid sight even when not in flower but now a sad looking thing. The leaves seem to be shrivelling up and it has bloomed but sparsely. Sample enclosed for your comment please.—R.W. (Chch). The trouble with your bottlebrush is a very bad attack of thrlpsi These sap-sucking insects tend to curl and

severely distort the leaves, many of which eventually dry and fad, leaving a rather denuded shrub; small plants which become badly infected by these insects may even die. Remedial measures to follow include over-all pruning (and immediate burning of the clippings) and at least two thorough sprayings with maldison at not more than 10-day intervals. This season I grew some egg plant in my glasshouse, unheated. The plants grew satisfactorily and produced numerous flowers but did not Set any fruit. When I noticed this happening I set about to hand pollinate but found the nature of the flowers such that the pollen was "nonremovable," In contrast io marrows, etc. At a guess, it would appear the flowers should be self-fertile. Could you please put me on the road to success?—"X" (Chch). As you will be aware, egg plant is a sub-tropical plant and in consequence the lack of heat in your glasshouse would react adversely against it. Egg plants require warm conditions over the entire growing period (in the vicinity of five months) to set fruit and give a satisfactory return of high quality. Long periods of cool weather can damage or seriously retard plants, and they are consider-

ably more sensitive than tomatoes in this respect. Cold conditions would affect the pollen as well aa pollination, and fertilisation. Would you please comment on the enclosed potatoes, Ham Hardy, many of which have this year turned cut to be similarly affected. The ground gets a bit of compost put on it but that's about all. I try to switch the crops around a bit too so that they are not grown in quite the same place each year. Is it a disease? They don't taste much different whether they have these holes in them or not.-—FJ. (Kaiapoi). The problem is associated predominantly with prevailing climatic conditions at ths time the potatoes are developing most rapidly and is commonly known as hollow heart. Fluctuating weather, which induces flushes of strong growth instead of even development, results in the outer cell layers of the tuber growing at a faster rate than the centre causing a cavity to be formed. Some discolouration is occasionally evident in the vicinity of the hollow but there Is otherwise nothing wrong with the potato as an eater. Incidence of hollow lieart can be very much reduced by keeping an even soil moisture under dry conditions.