GARDENERS’ QUERIES

Press, Volume CXI, Issue 32588, 23 April 1971, Page 11

GARDENERS’ QUERIES

Some of my French beans did not “fill.” This year not ail had the white mildew spots on the skins but some did. I had some sawdust in the soil but otherwise nothing different from other years—“ Beans” (Christchurch). The major contributing factor to your poor crop of beans is the presence of the fungus disease scelerotinia. This was in an advanced stage and is characterised by the white woolly growth and the black fruiting bodies in and around these infected areas. Unless extreme precautions are taken this disease, which can cause severe losses in other crops, also can remain viable in the soil for several years, germinating and attacking plants when conditions are favourable for it. It would seem from your letter that it has been previously established. The sawdust would not be contributory to its presence. All plants showing signs of disease should be carefully dug up and promptly burnt. The soil should be sterilised by applying formalin 1-50 to the point of saturation. The ground should be covered with a sheet or similar cover and left for two weeks. Thorough aeration of the soil is necessary before further planting or seed sowing can be contemplated. Apart from this disease, caterpillar damage and spider mites were evident. Beans are a sensitive crop and do not thrive unless everything is going for them. Two grape vines, bought as Muscat of Oman, produced huge bunches of flowers last year and the year before that also, but no fruit formed. They were cut back very severely and a number of bunches of grapes of extremely small dark purple berries have formed. Is the fruit likely to increase in size. Blood and bone is used in small quantities.—P.A. (Ashburton). There is no way of increasing the size of your grape. It is one of the currant grapes, which is naturally of small size. The name you have been given for it is incorrect and is also one that does not appear to be listed. It should be noted that blood and bone is not a balanced plant food as it does not contain potassium, a vital element in plant nutrition. Applications should generally be supplemented with sulphate of potash—a recommended

mixture for grape vines being 3oz blood and bone and loz potash to the square yard.

The tips of some of my chrysanthemums have some bright brown attachments on them. Could you advise what they are and whether they should be left? “M” (Christchurch). The flowers have aphides on them which need controlling. Spray with malathion at this stage.

We are interested in growing some climbing plants around the numerous

trellises, etc., which we have stripped of climbing roses. Could you please make recommendations of predominantly flowering and berried plants which could be grown? “Thornless” (Christchurch). Stauntenia hexaphylla (edible plum shaped fruit); Billardiera longiflora (cream and blue flowers, edible purplish berries); Vitis heterophylla (porcelain blue berries); Sollya fusiformis (blue flowers, purple berries); Passion fruit; Celastrus scandens (orange pods, red seed); Berberidopsis corallina (red flowers); Gelsimium sempervirens (yellow flowers).

I would like to know about growing rhubarb. I have eight crowns growing in sand and some time ago I dug in fowl manure and gave each crown a small amount of nitrate of soda. The leaves on each stalk seem to be huge, some about 12 inches across—is this in order? Do crowns grow all the year round, do they require much water and when should they be lifted and replanted? “D.P.” (North New Brighton).

Rhubarb does best in soils high in organic matter, nutrients and the presence of moisture. A medium acid soil is preferable and good drainage is essential—a factor which you will certainly not find a problem. There is a high requirement for potassium and an annual side dressing of a complete fertiliser (1:2:1) at 4 ounces a plant will be of benefit. In addition two or three additional boosters of a nitrogenous fertiliser such as nitrate of soda or sulphate of ammonia after initial pickings are worth while. Large leaves are a feature of some varieties. Replant, by dividing crowns, every four to five years.

Our Meyer lemon tree seems to have a disease. Could you advise how to eradicate the problem?— “Green Fingers” (Ross).

The “disease” is so called sooty mould, a fungus which thrives on the exudations from various scale insects, mealy bugs and aphides, giving the foliage and often also fruit and stems an appearance that looks like a coating of soot. A very heavy infestation of scales is responsible in this case. Control is achieved by spraying with summer oil, at tr: rate of 5 fluid ounces oil to a gallon of water.

Could you give a list of plants suitable for growing in a centrally heated house around 65 degrees in winter.—H.K. (Christchurch).

This is a difficult question to answer as other factors are involved apart from heat. Light intensity and humidity are ver' important aspects which must be considered. A hot dry atmosphere can be very detrimental to almost all foliage plants and such is usually the case in centrally heated places. The following are some plants reasonably tolerant for such conditions: sanseviera, cacti, chlorophytum, billergia and pilea.

Apples for identification. — “Flavoursome apple” (Lincoln): The specimen might be a Ballarat seedling, but it appears to be misshapen and I cannot identify it positively. W.R. (Oxford): Sorry, I cannot help.