Gardeners’ queries

Press, 23 June 1978, Page 5

Gardeners’ queries

I write to ask about treatment of celery spot. Both leaves and stems have small brown spots which cause the leaves to wither. They do not appear to be rust spots and sprays of zineb and copper oxychloride have had no beneficial effects. The plants are not growing in the same place as they were last year. — M.S. (Timaru). The symptoms referred io above are typical of celery leaf spot — in this case, severe infection. This fungus disease is the most prevalent and destructive affecting celery, and may occur wherever is it grown. Once it has gained a firm grip on plants it becomes impossible to eradicate and difficult to control. Avoid carry-over in the soil or'compost of diseased plants. Use only good seed and apply control at fortnightly intervals from about seedling stage onwards. This disease can also be spread by rain, wind and insect and is* favoured by the presence of moisture. Benomyl, zineb and copper-based sprays are all effective controls. Could you please advise me why my hydrangeas do not flower very much. Some bushes might only have two or three blooms on them. I suspect it is ail in the pruning. Do 1 prune before or after the winter — G.P. (Chch). Hydrangea buds are susceptible to frost damage. As they are likely to be stimulated into growth from pruning it is best to delay this action until later in the .winter or even early Spring where they are growing in very cold areas. This is nor really so necessary in places where hard frosts are unlikely. It is possible that poor blooming in your plants was due to pruning technique. Flowers originate from the plump double buds and also from terminal ones. Wood buds tend to be very much less conspicuous. Plants grown in heavy shade and poor soil and badly crowded or suffering from strong competition from trees and shrubs may also produce less bloom. They respond to the adddition of compost. Please could vou tell me how to keep my geraniums alive during the severe winter we have here. We have had a few hard frosts but the geraniums are still alive in the garden. We are getting rain now. Should I move the geraniums? — C P. (Twizel). It is best to )ea\e the pruning of geraniums until early spring. The cover afforded even hv partly withered growth will rive the plants protection from hard frosts to which they would otherwise be fully ex-

pused. Glass or a clear polythene frame would give added protection if well placed when some of the upper growth could be cut back. Another alternative is to lift the individual plants and pot them up. They should be placed in a frost-free place in full light and should be cut well back. Hardening ofl’ is necessary before replanting in the spring, otherwise the young growth is likely to suffer. Keep the soil only just moist and no more.

I have a "Ville de Lyon" clematis on a slope and getting very overgrown. I should like to know if it would be possible to move it. It is 15 years old. If this is possible how would I go about it and when. Also, we have a yellow tamirilio which is fruiting well, although almost 12ft high and very stalky. Would it be safe to cut it down to half its height? — "Clematis" (Chch). The clematis ‘’Ville de Lyon” flowers on curreni season’s growth. As such it will tolerate hard cutting back which will be desirable in order to transplant it. As you live on the hill this task could be accomplished now otherwise it would be best to wait until the end of winter/ early spring. Every effort should be made to retain as much root system on the plant as possible. Before replanting, make sure to trim back all damaged or long roots. Tamarillos fruit on wood of the current season and as such require judicious annual pruning not onh to keep fruiting at maximum potential but also to stimulate new growth and prevent legginess, which has occurred. The timing of pruning influences the time of maturity of the next crop. Pruning is done in springtime and so the earlier it is done then the sooner will there be mature fruit.

Is there a correct time to prune grapes — say, before the frosts start or after. How is it that on a bunch of grapes I had some fully developed beautiful grapes and yet so many immmature ones about half the size of a garden pea in the same bunch. What spray could I use during the growth of the grapes before they start to ripen to destroy spiders and other insects? When the foliage is dense it is difficult to get the spray into the centre of the vine. Should I remove some of the foliage? — "Grapes" (Ashburton).

Grapes can be pruned from anv time after the leaves have commenced to wither and fall off until late winter — say. early August If pruning i« left anv longer the rise in the .sap flow will mean that all pruning

cuts will bleed, a situation j which is detrimental to the i health of the vine and also one ' which is impossible to stop. ' The usual reason for the ap- : pearance of undeveloped grapes I such as you describe is in- ■ sufficient pollination. To assist . in the fullest development of ■■ berries on the individual | bunches some thinning out can . be done and immature fruits I could be removed. Carbaryl is ! recommended for the control | of all chewing insects and i spiders on grape vines. In order to assist ripening of the . fruit and improve ventilation ■ to the vine, summer pruning < is desirable, a task which can : be done in late December and i early January. I have been trying to locate a nurseryman who stocks Zelkova serrata, a tree which you wrote about in an article recently. I wondered if you could help. — A.F. (Wairhate). As was mentioned in the • article the tree is both un- | common and not readily obtain- . able. However, Cashmere i Downs Nursery have currently j got a few specimens available.