Gardeners’ Queries ...

Press, Volume CI, Issue 29797, 13 April 1962, Page 7

Gardeners’ Queries ...

Could you advise me about the selection of trees for a drive? Last year we planted 25 silver birch 12ft apart. We had very cold southerlies that withered the foliage, and later it was so dry that we lost the lot. (Mrs C.P., Ashburton.)

There was nothing wrong with your original choice. Silver birch is quite suitable for your locality, and will grow quite happily on thin soils. You did not tell me the size of plant you used, but I suspect that they were too large. Where conditions are liable to be dry the best plants to use are the smallest. Birch always tend to sulk a year in any case if asked to tolerate dry conditions when planted too large. Give them a second opportunity, using small plants—a foot tall —and give water in a dry spell in the first season.

I am sending you two peaches off my tree, typical of the whole crop. They are all infected with gumming inside the fruits. The tree trunk and leaves look quite healthy. The tree has been like this for several years, and I would be glad if you could suggest something to improve the fruits. (“Puzzled,” Kaikoura.)

This trouble is known as gumming, and its cause is not known. Numerous suggestions have been made, such as excess water in the soil, too little soil water, poor soil conditions, bad drainage, and so on. It is possible that the application of Phygon sprays at 1 in 1000, applied at threeweekly intervals’ from blossom time onwards, may help to control the trouble, but it is only a possibility, not a certainty. I am sorry I cannot be more helpful, but this trouble is quite a problem. What is this trouble which is attacking my carnation plants, and what is the cure? Purplish spots and splotches occur on the leaves, they join together, and parts of the leaf die as a result.— ("Puzzled,” Hokitika.) This trouble is a fairly common one—carnation leaf spot, or septoria, as it is sometimes called. The tiny black specks on the leaves are the spores which spread the disease. Control is partially cultural, for syringing will spread the disease, as will rain, of course. Sprays of either Bordeaux mixture or one of the dithiocarbamate sprays, such as Dithane, will control the disease, although it will not improve severely affected leaves.

Would delphiniums do well against a wall facing north? I enclose a shrub with pendant red and yeUow flowers. Could you tell me the name and how it should be pruned? (“Interested,” Papanui.)

Delphiniums would grow satisfactorily here if they are staked against wind—nor'-west winds would bounce off the wall—and if they can be given adequate water. I think they would cause a certain amount of work in this position. Agapanthus would be a much better choice —it’s blue flowered, is rather later and shorter in height, but it would thoroughly enjoy this warm, dry situation. Your shrub for identification is Abutilon megapotamicum. It does not need regular pruning, but if plants become overgrown they should be severely thinned. Do not chop it back to an even height thinning out the branches. which should be carried out about every other year, will give a much more shapely plant. 1 have a 20ft cedar tree which some previous owner topped at * height of about 4ft. It has given rise to four trunks, and I would like to remove two of them. Would the tree be too old to fill the gap left by their removal? Could the tree be satisfactorily topped now? It keeps most of the winter sun off the house. (Mrs E.C.. Papanui.) I do not advise either operation if you want the tree to retain its appearance. The huge gap left by removing the trunks would not fill up. and if top-

ping is carried out it would leave a travesty of a tree rather than a presentable specimen. It would appear that the original planter gave insufficient thought to the passing of the years, a sad but common state of affairs where tree-planting is concerned. What could be a delightful specimen now is condemned to mutilation or ’ removal due to lack of foresight.

I am working up the ground in my orchard and intend to plant a large quantity of lettuce and cabbage. The soil is full of the enclosed weeds—-one with a clover-like leaf and the other having a blue belllike flower. Is there anything I can apply to the soil that will get rid of these weeds?—(C.G., Kaikoura.)

This is a very tall order, for you want a weedkiller which will kill the weed roots, will not harm the apple trees, and will also leave no residue in the soil to harm the cabbage. The clover-like weed is Oxalis, a most difficult weed to eradicate, whilst the other is Campanula rapunculoides. This latter plant is often cultivated, but can be invasive when it gets out of hand. There is no specific control for oxalis as yet, and this weed can only be controlled by chemicals such as methyl bromide which will kill other plants as well, although it has no residual effect. I can find no information whatever about the control of the campanula. It is quite possible that 2.4-D may be effective, but you would have to apply it to contact the leaves. It would be valueless applied to the soil. I am sorry I cannot help you further. but this is an almost impossible proposition. The hoe is your only answer.

I enclose a weed which is taking over my lawn. I have tried the sulphate of ammonia dressings but have had no success with its control. Can you recommend anything? (Mrs T.G.W., Hornby.) Two weeks ago there was a letter in this column requesting an opinion on dichondra as a plant for a lawn. Today the wheel has come full circle, for you are requesting information on how to control dichondra! This prostrate plant with its kidney shaped leaves is sometimes used for bowling greens in some parts of the country. Where it occurs as a weed, it can be controlled with the aid of the hormone weedkiller 2.4.5-T applied at the rate of 21b of active chemical per acre, or in proportion.