Gardeners' queries

Press, Volume CXIV, Issue 33513, 19 April 1974, Page 4

Gardeners ' queries

Our lawns are lower than the concrete paths but, they are cut about two inches away from the path. Can you suggest anything I can spread in the hollow to prevent weeds growing? I can cut the edges with long shears but have to get down on my knees to dig the weeds out. — M. H. (Belfast).

It is hard to understand why this form of lawn edging was introduced and perpetuated, as it always means extra work in one form or another. The best and most practical method of overcoming the problem is to fill the intervening area with soil and bring it up flush with the path. Could you please identify this self-sown climbeu* Is it a weed, or something that will flower? Do you know what is attacking the tips of my firethom shrub? Then, once more, the oxalis problem. Is it possible ever to get rid of it? I have weeded my borders meticulously at least four times this season, but it keeps coming up in abundance. I cannot believe I miss out hundreds of bulblets each time, but if, for example, every bit of broken root is capable of striking again, I feel my efforts are a waste of time. Is this fineleaved specimen a form of oxalis also? One of our apple trees is so badly infested with woolly aphis that we cannot even sit in its shade without getting sticky. Can I do anything about it at this time of the year? I have a bag of two per cent Lindane dust, but with instructions only for working it into the soil. Can I use it in a spray, and at what strength? Would it mix with oils or Bordeaux? — M. E. (Christchurch). The self-sown climber is a species of clematis which has small flowers. Leaf-rol-ler caterpiller is responsible for the damage to the firethom, the control for which is D.D.D. carberyl. Oxalis will germinate from every little bulbil left in the ground, however small or large it is. Plants disintegrate very easily when the soil is disturbed in their vicinity and bulbils are easily dispersed in consequence. The only control is by means of soil sterilisation with chemicals such as mylohe. This is a dangerous gas when released and it requires thorough application to be effective. It cannot be used near valuable plants and is not available to the general public. There are many species of oxalis, some of which are not as invasive as others. They are even grown as ornaments in some countries. Control for woolly aphides should consist of an application of red (winter) plus lindane in winter and lindane at green tip. Lindane could be applied now to the infested apple tree, provided all fruit has been picked. Lindane wettable powder can be safely mixed with most commonly-used fungicides and pesticides. The usual strength of this material as a wettable powder, is 50 per cent — very much ihore concentrated than your dust. To be as effective any dosage of the dust would have to be 25 times the recommended strength for 50 per cent wettable powder. Enclosed are specimen leaves of my waratah. The young shrub Itself was just under three feet when planted five months ago. It was very healthy and grew rapidly. But for two months now the leaves have discoloured, dried and fallen off. The stems appear healthy. Could you give cause and remedy? — J. M. (South Brighton).

Waratabs do tend to shed their leaves, but whether the enclosed has fallen through natural causes or not cannot be determined. There is no suggestion of disease, though. It is possible your plant has exhausted the available nutrient supply in the soil around it — waratahs respond to nitrogen and, to a lesser degree to potash. The addition of one eight of a kilogram (approx. 4 oz) blood and bone scattered around the plant could be beneficial.

Could you tell me whether this toadstool is poisonous, or if it can be eaten? — E. W. (Christchurch). Sorry, but to answer a question of this nature a complete sound specimen is essential. The bit you sent had virtually disintegrated by the time it reached me. Could you let me know if there is anything wrong with my magnolia? It has made a lot of growth but the leaves are always disfigured with black spots. Then they turn yellow and drop off. Also, could you give me the name of the

other plant, and is it an indoor one? — G., B. (Christchurch). The magnolia is afflicted by a fungus leaf spot. This can be controlled by periodic applications, early in the growing season, of a copperbased spray. The specimen leaf appears to come from the Mexican plant known as boat lily also commonly called. Moses in cradle! It is an indoor plant which likes to be kept moist and in diffused light.

Is it true that squash and pumpkin cannot be grown successfully together? Last year a seedling pumpkin produced five large pumpkins. This year I grew six pumpkins and two squash plants, well separated, manured and watered. They flourished and flowered well but the total crop has been four

medium-sized pumpkins and two small squash. — I. L. (Christchurch).

There is no truth in the assumption that pumpkin and squash cannot be grown together. Variability of fruit sown from either pumpkin or squash which were grown close together, however, is a possibility 7. The major influencing factor in crop production of cucurbits is the weather at the time when the pollen is ripe and the female flowers are receptive. Can you please tell me If the enclosed plant is a grapevine? It was sold to me as such but after five years we have not had any grapes. — M. C. (Christchurch).

By the time this query was received, in a very round-about way, the specimen was in too desiccated a condition to identify in detail, but it is a species of grape.

Last November 1 put three avocado stones into a pot, and they are now showing shoots. What can I da with them? Should they* be kept as indoor plants all their, lives, or only until frosts are over? How decorative are they? Will they ever bear ripe fruit in summer? — D. M. (Christchurch).

Seeds from imported avocadoes are generally unsuitable for germinating here if fruiting is desired, because they are probably from a tropical variety. Only the more hardy varieties are selected for growing in New Zealand and then they are

more or less confined to the upper part of the North Island. The avocado can stand only very light frost, but any frost will damage fruit buds or flowers. As such it takes up to 10 years for a seedling to come into fruiting, which is why grafted stock is recommended; also two varieties are desirable to increase the efficiency. of cross pollination. Fruiting apart, these plants make attractive-foliaged ornamental tub. plants.

I would like to know how to prevent Cox’s orange apples from going brown-spotted in the flesh. The apples looked perfect from the outside, but when peeled the small brown spots were deepseated and made a lot of waste apple. — “Bitter pit” (Ashburton). Judging by the nom de

plume it would ' appear you have an inkling of the cause of the complaint, for it is

bitter pit. This is predominantly a physiological problem to which some apples, such as Cox’s orange, pippin and Lord Wolseley, are more susceptible than others. The use of calcium nitrate at 14-day intervals, from two weeks after full bloom until harvest, is still regarded as the most effective means of control. The application rate is 28 grams (1 oz) calcium nitrate to 4.55 litres (1 gallon) and a drop of a .wetting agent. I have had little success in striking photinia robusta cuttings. Most grew and were then periodically attacked over the summer, the leaves blackening at least in part. Some second growth on the enclosed cuttings has also been lost. Can anything be done to prevent this next time? — G. S. (Christchurch).

Fire blight, a bacterial disease is the cause of this trouble. It is spread in several ways, including through pruning tools and insects. It attacks many plants of the Roseaceae family, some of which act as major hosts. Where infection occurs branches must be cut back at least 30.5 cm (1 foot) below the last visible signs

of infection. Bordeaux mixture helps, but the anti-bio-tic streptomycin provides the best control. The source of your cuttings could be infected or there may be a carrier of the disease such as a hawthorn hedge nearby-