Gardeners9 Queries...

Press, Volume XCIX, Issue 29389, 16 December 1960, Page 11

Gardeners 9 Queries...

I am keen to grew good polyanthus, but so far do not seem to have had much success. Plant* start off well enough, but by flowering time they seem to go back, producing only a single bloom each, and having pale green or yellowish leaves. Can you suggest a cause? (Polyanthus, Christchurch.)' This is not easy without seeing the plants and their conditions of growth. It could be due to several factors, such as soil, position, or pest attack. I would suggest the following as possible approaches to better growing. Make sure that you have no pests such as grass grub, at the roots of your plants by mixing D.D-T. Super with the eoil before planting at 3-40z.t0 the square yard, Secondly, don’t plant in a hot, dry position—choose a cool moist place for preference. Give a light dressing of sulphate of ammonia, at about l-2oz per sq. yard, in the early spring. This should be scattered on the soil only, not the leaves, and stirred into the soil. A light, sandy soil is not a good soil for polyanthus, and should, be • improved with dressings of organic manure, such as compost or stack bottom.

I wonder If you could identify the following troubles for me and advise on the cure? Specimens are enclosed. (Interested, Hari Harl, South Westland.)

The rose, which has small orange-red spots on the leaves, is attacked by the rose rust disease. A good combination rose dust should control this as well as other troubles. The nectarine and peach are both attacked by peach leaf curl. See the answer to the earlier correspondent on this page. The nectarine fruit is attacked by the disease which causes "plum pocket.” This is fairly closely related to leaf curl. The fruits don’t swell properly, and form flat, shrivelled pouches, which may produce a whitish bloom on their surface. The only effectual control is the removal and destruction of attacked fruits and the shoots which produce them, to remove the source of infection for next year. It is less prevalent in dryer areas. For some years I have been unable to control mildew on apple trees. I have used * full strength lime sulphur spray after leaf fall, and during the growing season have used several sprays of a cureall mixture, consisting of lime sulphur, lead arsenate, dehydrated lime, Black Leaf 40, detergent, ahd water. This has been mixed and used as a stock mixture when required. In addition, mildewed growths have been removed and destroyed, but the attacks come just as bad each year. Where have I gone wrong? (Perplexed, St. Albans.)

The mixture and concentrations you gave should have given you adequate control of mildew. Lime sulphur is excellent on fruit for this purpose. Where you have gone wrong, I think, is in using this mixture as a stock mixture. Lime sulphur and lead arsenate react with each other, but the reaction is slow enough for them to be applied in the same mixture if it is not allowed to stand. When the mixture stands—as it does in a stock mixture—then Calcium arsenate is produced, which has no action against apple mildew, and indeed, may cause damage to the tree. Try again next year using freshly made up material, and you will have success.

I have a “Queen Elizabeth" rose which has been excellent each year till now. This year it has deteriorated—there are fewer flowers, and the leaves are covered with a sticky substance and some have withered. Can I do anything about it? (Rose Grower, Papa-

nul.) Without seeing your plant I cannot be specific—it could be a number of things causing this trouble. However, it sounds very much like a severe attack of aphis, which has a very debilitating effect, and would give rise to the lack of vigour this year. The stickiness could result from the honey dew secretion of the aphis as they feed. A good spray

with any of the recognised aphis killers—malathion, or Black Leaf 40—should clear up the infestation, so that subsequent growth will be more vigorous. Add a little detergent to the spray to make sure the rose leaves and shoots are adequately wetted by the aphis killer. I have two troubles which I would appreciate advice on. The leaves of cinerarias recently planted out have been perforated with some insect pest. I have been applying Nexa with some success, but the trouble Is not yet cleared up. I also have a plant of Erica wilmoreana, planted in a warm sunny spot last August which has remained stationary in sise. What can I do to make it grow? (AJMLD., Spreydon.)

Could I remind you that patience is a virtue? Nexa should have the desired effect in clearing up the caterpillar infestation, but of course, will not mend the leaves already damaged. Make sure that you cover the whole plant when spraying, both upper and lower leaf surfaces. It is easy to miss small caterpillars hidden away. The Erica will grow, never fear, but give it a chance to get started! It may be slow because it is not getting quite as much water as is desirable in the young stages. If it is on a north wall then it won’t have had much of the rain we've received lately, so give it a good soak. Then just wait! Don’t, forget to give it protection in hard weather this coming 'winter—Erica wilmoreana is not the hardiest of heathers. As coarse sand seems to be. invariably recommended for making heavy soils more friable, is it worth while to buy the only sand that contractors deliver—namely fine sand? (M.G.S., Ferry road.) Coarse sand is available. We have purchased “propagating sand” and Kaiapoi grit at the college, both of which contain up to about 50 per cent, of coarse sand. If you want very coarse material, then l-Bth grit is a graded sand—or really a fine gravel—which is excellent for opening up heavy soils. We have been using this material for the last year or so in potting mixtures with a heavy soil, and have obtained excellent results. Cost is about I7s 6d a yard, in bulk.