GARDENERS’ QUERIES

Press, Volume CXII, Issue 32879, 30 March 1972, Page 13

GARDENERS’ QUERIES

I should be most grateful if you could identify the enclosed specimen which has been in flower for the last month. The flower heads grow on stems 2ft tall and the dump has gradually increased in size since it first made its appearance several years ago. —A.A. (Chch). The plant is alstroemeria, a most attractive little plant and one which is, surprisoften seen in home

I am enclosing two potatoes and would be grateful if you could tell me the cause of the scab on them. I grew them on grassland. They were not sprayed. When you spray potatoes do you spray the ground under the leaves as well as the plant? Also my marrows have a lot of powdery white on them. Is this from water on them?—“lnterested” (Lyttelton).

The scabby nature of your potatoes is indicative of potato scab, a problem associated with soils which are not acid enough, and more prevalent in warm dry spells. It does not really affect them very much and is usually overcome by refraining from liming and by using acid fertilisers such as sulphate of ammonia. Spraying cannot overcome the problem although dipping the seed in a mercury solution is sometimes a commercial nractice. Powdery mildew is most probably the cause of the powdery deposit on your marrow leaves. This can be controlled by spraying the plants with karathane. When spraying potatoes the application should be directed predominantly on the foliage both above and below the leaves and also on the stems. There is no need to spray the ground round the plant. We have an Omega plum tree which is covered in blossom each year but the fruit does not set. Is it necessary to have another tree of the same variety?— G.C. (Greendale). The Omega plum, which is also known as George Wilson, is regarded as fully selffertile and capable of setting a crop of fruit with its own pollen. The addition cf suitable pollinators always enhances any fruit crop and such varieties as Early Sultan, Victory and Elephant Heart are suitable in this 1 case. It is very possible that ’ the blossom on your tree is 1 damaged by frost. < . I read your article on ' control of leaf curl on 1 peaches. Would this treat- 1 ment be satisfactory for a 1 nectarine tree? This tree 1 b about three years old. Each year the first leaves curl and drop off and later a new growth occurs. This year the first fruit appeared. The branches were literally covered but the fruit dried and dropped off. —HJC (Chch). The treatment for nectarines is exactly the same as that applied to peaches in all respects. Where leaf curl is repeatedly severe it can attack even the second flush of new leaves and eventually it has a detrimental effect on the tree’s health and vigour. It can cause flower drop, and also distortion and premature fall of fniit. 1 am wondering whether

to lift my Red Gauntlet strawberries this year. This is their second year in the ground. They have cropped very heavily. What is your oponion?— H. H. (Riccarton). Generally, three years is the maximum one should retain strawberry plants in the home garden. Where cultural ‘ attention has been poor even • this period of time may not ’ prove worthwhile. To avoid ’ having to replant the whole

crop every two or three years it pays to replace a few plants every year thus giving “new”, “established” and "last year” plants in the bed. Enclosed please find specimens of Kidd’s Orange and a Meyer Lemon. (1) What has caused the watery texture in these apples — something lacking or watering at the wrong time? (2) Is the spongy skin on the lemon the result of being overripe, or is it a disease? — H. R. (Christchurch). The apples have a physiological problem which is known as watery core. This disease is more pronounced during seasons of high temperatures and is accentuated where the weight of developing fruit causes the branches to bend, thus exposing them to direct sunlight. Another contributory factor which has been found

: conductive to watery core, ; particularly under the above , conditions, is excessive use , of nitrogen. It is more pre- ; valent in some varieties such ’ as Delicious than others, and irrespective of what little preventive measures are possible there will always be a few apples which will suffer from watery core. The lemon appears to be over mature; they should be picked well before this stage, when of reasonable size. For the past two seasons our French beans have been a failure. They are very healthy until after the flowers fall and the beans begin to form. The leaves then turn yellow with brown specks and the beans though a good size have a blight on them. We have sprayed without success. — Garden Lover (Opawa). Halo blight, a bacterial disease, is the cause of the water soaked spots on the beans and the discolouration of the leaves. Surprisingly enough, although tills a a universal disease which occurs whereever beans are grown, only one or two queries in the last few years have dealt with it The disease is seed-carried and also is carried over from season to season on infected crop residue. During the season spread is by insects and by rain. Crop rotation and the prompt removal of any diseased plants as they show up are of primary importance in control. Apart from that an application of copper oxychloride should be given when the first true

leaves appear followed, by two or three additional applications at monthly intervals depending on whether it is dry or a normal season. There is considerable variability in the susceptibility of beans to halo blight and

in general it has been found that white seeded varieties and runner beans are the most resistant. Enclosed please find samples of twigs from a Cox’s Orange apple tree. The fruit has ripened enough to be eaten so I have removed all fruit and sprayed the tree with summer oil. What is the trouble and what further treatment do you advise?—“Apple Lover” (Timaru). The problem in this case is a severe manifestation of woolly aphides. Whilst summer oil is useful, lindane is preferred; red oil should be used in winter and lindane applied again at green tip. Woolly aphides should not be allowed to remain as they will cause blindness of the buds.

Could you tell me how to kill a very old apricot tree which bears very little fruit. I have already ring barked the tree. I have been advised to chop it down and paint with 2, 44-T. In view of the pre- ' sent controversy over its , use perhaps you might be : kind enough to suggest an 1 alternative method of destroying the tree.—E.B. ; (Sumner). Complete ring barking will kill the tree, but death can be appreciably speeded up by , swabbing with 2,4,5-T or picloram in late winter or early spring. I am enclosing some pears from a tree. Two of them are very mis-shapen and the other two are fairly good specimens. Could you please tell me: SThe variety of the pear; Why some are misshapen—there are quite a number of similarly misshapen ones on the tree, and how to overcome this. —G.C. (Bryndwr). The mis-shapen nature of some of the pears is due to a disease known as stony pit. Once a tree bears this virus infection, which is transmitted only by means of budding or grafting with infected wood, it is not eradicable. Although a tree suffering from stony pit may produce a considerable quantity of perfectly normal fruit, the percentage of which may vary from year to year, it does not pay to persevere with it where crops are predominantly stunted. The variety looks like Packhams Triumph. If you do remove the tree be sure to get a suitable pollinator for your Bon Chretien—varieties such as Beurre Bose, Winter Cole and Winter Nelis plus the above are suitable.

Could you please tell me what makes the leaves go yellow and fall off my rubber plant? This is the fourth plant and they all seem to do the same after about ten months. I have been told that is due to too much watering but I have refrained from doing that Also when does one break up an arum lily which has got too large?—LP. (Christchurch). The problem is physiological and is associated with the cultural attention received or the environment in which it is kept, or both. Rubber plants do not like draughts, over watering, standing' in water or water-logged soils; they resent being placed in close proximity to any heating appliance although they like a dry atmosphere. Arum lilies can be broken up and replanted now.

Could you tell me what tills plant Is?—“Keen Gardener” (Ashburton). The plant is a helianthemum or rock rose, a most useful subject for draping over walls, rock gardens and similar situations. They are hardy, fairly draught resistant, but not, comparatively, long lived.

Could you please advise me as to why our 10 strawberry plants failed to even have a flower on? They are Red Gauntlet and the ground was prepared with compost, ashes and animal manure and the foliage large and healthy.— (Kalkoura).

One of the most likely causes for the failure of flower development is the use of excessive amounts of nitrogenous manure which always causes excessive growth at the expense of flowering and subsequent fruiting. This would seem a most logical explanation in your case.