GARDENERS’ QUERIES

Press, Volume CVIII, Issue 31753, 9 August 1968, Page 6

GARDENERS’ QUERIES

I bought a standard rose (Virgo) at the beginning of June which showed signs of disease at the tips of some of the shoots; otherwise it seemed to be a strong, healthy specimen. Now most of the ends of the shoots are showing a considerable amount of dieback and there are dark brown patches near the base of three of them. The rose is In a fairly sunny spot near other standards which are doing well. It was planted according to instructions, well-watered and no manure has been used. Is there any control for die-back and what causes this condition.—G.K. (Christchurch). It would seem that your rose is suffering from a combination of die-back and blast which may be part physiological in its inception, although blast is a bacterium. Careless pruning or mishandling can lead to die-back and the only remedy is to cut back to healthy tissue. From your description it is doubtful whether your plant will survive. The use of a timely spray with Bordeaux mixture sometimes is of help against blast.

Coaid you please answer the following questions: (1) Is there any way ot promoting growth of a central trunk, e-g., by grafting on to a Grevillea robusta (approximately 10ft high) which lost about 3ft of Its growing tip during the Easter gale; (2) What Is the comet method of pruning a 4ft high Prunus cerasus Amanogawa; (3) At what age does an omega plum become capable of crosspollinating a purple king plum; (4) I am contemplating using gasworks ash for a gravel path. Does this ash contain any substance which by leaching could harm flora in the adjacent garden. R.H. (Christchurch). After initial shaping of the tree along the usual lines employed in pruning young fruit trees, little, if any, pruning of flowering cherries is needed. Initially, a number of leaders are established from the main trunk, wellspaced and emanating from different parts. Once flowers are produced on a plant, pollination is possible, irrespec-

tive of its age. The omega or George Wilson plum, however, is not a pollinator for purple king, which could benefit from the presence of another Japanese variety such as October Purple or Doris. The cherry plum is also suitable. Omega is selffertile. As far as I can ascertain there should not be any harmful effects to plants from the use of ashes mentioned. Grevijlea robusta is not fully hardy and grows into a large tree. Grafting is a possibility, though I have not tried it or heard of its use on Grevllleas. You could try. Preferably train a lateral upwards.

The enclosed sample* of leave* of my Garry* •IMP’ ' tie* teem to indicate tome kind of dl*e**e. It ha* started in the lower foliage and la alowly spreading. What I* It and could you advise of treatment to give?—LT. (Christchurch). A heavy infeatation of scale* it causing the dluoloration on your Garry* elliptic*. Apply white oil as toon at pottlble.

Can vegetable* and fruit tree* absorb into their t|*> me* through leave* and/or root* the accumulated toxic residue* of spray* in tach an amount a* to make the vegetable* or fruit unit for consumption? If •*, aye there effective spray* with little or no toxle reeldue? “Orchard” (Christchurch).

Many chemical* are extremely dangerous if handled, carelessly both befere.during. and after application to plants. Tor this r*a*en tom* material* are available only to commercial grower*, and other* mutt be signed for when purchased. In all case*, makers’ recommendations alfe to be followed and a prescribed waiting period it set down for particular materials. This is reviewed annually. For instance, crops sprayed with carbaryl are fit for con-

sumption on the following day, but menazon requires a waiting period of two weeks. Again some crops vary in their susceptibility to absorption. Potatoes become tainted If sprayed with D.D.T., and the use of D.D.T. precludes the consumption of all crops except berry fruits and tomatoes until four weeks after spraying. The former should not be sprayed after commencement of flowering, and the latter can be sprayed to seven days before harvesting. The publication “Pest Control Without Poisons,” by L. Hill, may be of interest to you.

We have a considerable problem with leaves every winter a* there are several large deciduous trees in and around our garden which has a good proportion of it devoted to shrubbery. The question is whether or not the leaves have value and if so should they be left to rot on the ground or put in a heap to do likewise.—“ Leaf Raker” (Christchurch). This is a vexatious problem to many gardeners as it is generally felt that fallen leaves left where they fall always look untidy and furthermore are apt to get blown about Those on the lawn should definitely be raked up as they can suppress and kill out the grasses eventually. In the beds they have great value, not only as a mulch but also as a means of improving soil fertility and providing humus. A rough forking over to partially cover them with soil or the presence of moisture will help to keep them from blowing about and an overall sprinkle of blood and bone or sulphate of ammonia will hasten breakdown. If they are composted by collecting, heaping up, adding one of the fertilisers mentioned and covering with a layer of soil will produce more rapid decomposition, and excellent leaf mould would thus be made. About seven yean ago we planted a pair of Chinese gooseberries. Growth has been very great but the male plant flowered the second year only (apart from one flower two seasons ago) while the female has flowered every year

from the third. Is there anything that could be done to encourage flowering or would it be better to get a new one. Last year we hand pollinated and have just finished picking about three dozen lively fruit. Pruning has always been the same for both plants.—R.W. (Rakaia).

I cannot offer an explanation of why your plant does not flower and it may pay to graft on some male scions from a reliable source by means of whip and tongue grafts. This should be done now or left until late July to early August next year.