Gardeners’ queries Of lemons and walnuts ...

Press, 11 June 1982, Page 11

Gardeners’ queries Of lemons and walnuts ...

I read with interest your remarks on lemon trees recently. Our Lisbon lemon has gone further than that and lost its leaves, although it still produces flowers and tiny, fruit. I have given it Epsom salts, and various animal manures, and the recommended citrus fertilisers. Some of the branches are dying, or dead. It is about eight years old. The other problem is the young walnut tree which produced walnuts for the first time; these were quite black, although the tree looks healthy. It does have some yellow spots on some of the leaves during the growing season, however. I should be grateful for suggested treatment for hoth these problems. M.A. (Diamond Harbour). The trouble with the walnut tree is most probably an attack of .walnut blight. This bacterial disease is the most prevalent of troubles to afflict walnut trees and becomes difficult to control in the case of large trees: it is carried over from year to year on infested buds and the severity of subsequent infection is dependant on prevailing weather conditions. Recommended treatment consists of applying either Bordeaux mixture, or copper oxychloride, plus white oil. The mixture should be ap-

plied at the following stages: 1) When about half the termi- ■ nal buds are open; 2) just before most of the female flowers are fully open; 3) when the young fruit is about the size of mothballs. Concerning the citrus tree, it is really not possible to provide much information without seeing the problem. It would seem that there could be a disease responsible for the shedding of the leaves, but there are other possibilities which could be involved as well, such as bad drainage (too wet), too dry. and/or too exposed. A shift of location may be the possible remedy — wrench it now and move it in spring time. I would appreciate advice on the following. 1) Have just been horrified to notice fasciation on my Daphne leucanthe. Should I prune these branches out now, or could I leave them to flower first? I suppose my bush is doomed. 2) Cottony cushion scale on hydrangeas, and this despite spraying with white oil during past several seasons, and even applying that oil neat with a paint brush to affected parts in the spring. Should we spray now with red oil. Why is it so persistent? 3) Suckers from rootstock of Apricot “Golden Glow” about four to five

years old. Unnoticed until now, when they are sprouting green leaves. The two suckers are growing beside the trunk, and are six to seven feet tall. Are these too big to rip off? 4) My Lady Clare camellia seedling (about seven years old) is sporting its first flower buds. You predicted several months ago that it would flower soon. Should be interesting, but there will doubtless be seedling variation. D.M. (Chch). Daphne odora ‘Leucanthe’ is prone to fasciation, an abnormality which will, however. not cause the death of plants. It can be safely left to flower before cutting back. Cottony cushion scale have become extremely prevalent in local hydrangeas. and where infestations have not been controlled it has led to accelerated loss of vigour and finally death of the host plants. The best time for treatment is in the winter months when the canes are easily got at. Spraying should be done following pruning, applying a thorough application of white oil, or lime sulphur. Prunings with scale on them should be burnt. It is essential to remove suckers from budded or grafted stock otherwise these will take over to the detriment, if not the demise,

of the cultivar. Even though the suckers in this case are large they should still be ripped out rather than cut off at ground level. A watch should be kept for any subsequent suckers and these should be promptly removed. Patience has been rewarded with camellia, and now the wait to see what sort of flower will appear! I have two feijoa trees that bear quite well, but are encroaching on the rest of the garden. Can feijoas be pruned, and if so. how, and at what time of the year? 2) A branch about 4 inches across was cut off a twelve-year-old wattle tree about two months ago, and the cut treated with a commercial ■ sealant. Ever since it has dripped a clear substance that has hardened. Why? Can anything be done to stop it? No similar-sized cut of this tree has resulted in this before. U.D. (Chch). Feijoas will grow into fairly large-sized shrubs when left to themselves, although some variability can be expected depending on the origin of the plant and where it is growing. Fruit is borne mainly on the outer regions of the branches and therefore judicious pruning and thinning can be carried out as

deemed necessary, but it should not be excessive; the same applies to height, which can be limited to suit convenience but should not be too drastic. Pruning should be done after fruit has either fallen or been picked, and can be left until early spring. It is not unusual for wattles to exude resin from large cuts or damaged branches in mid-season, but it is surprising to learn of this particular case, both from the period when it was done and the size of the cut. It would be necessary to have more details before commenting further. It seems very difficult, if not impossible, to stem the flow of sap or resin once it has started.