Gardeners’ queries

Press, 21 November 1986, Page 14

Gardeners’ queries

GARDENING

by

Mike Lusty

Could you please name this shrub which is just in the last stage of flowering for this year. It is rather open if not sparse of growth and has white blossoms but not many of them. Can It be improved in some way? B.H. (Chch).

Stewartia sinensis, one of a small genus allied to the Camellias, is the name of this plant. It prefers a coolroot run, a lime-free soil with leaf mould or organic litter in it to really thrive. Growth is slow but steady under suitable conditions. It makes a large shrub or small tree notable eventually for its peeling bark; the flowers are solitary and although never spectacular they are produced over some weeks and are fragrant. The leaves are colourful in autumn before they drop.

The enclosed sample of grapefruit is one of several similarly affected with small brown spots. Sometimes the flesh under these spots is brown also. The tree is in a frost-free position. How is it possible to prevent recurrence of this trouble? “Grapefruit” (Amberley). The symptoms displayed by your fruit are associated with the fungal infection wither tip, a disease which can also attack blossom, foliage and wood. Infected growth should be removed and the tree sprayed with a copper based preparation. This treatment should be repeated in three to four weeks time and again in mid autumn.

I enclose some flowers from a group of hazel nuts which I have had on hand for six years but never had a nut from. The bushes seem to be quite healthy and loaded with female flowers but there never seem to be many male ones. Could it be lack of fertilisation or another problem? D.B. (Rakaia). Although the hazel nut is monoecious (male and female flowers are borne on the same plant) it is also dichogamous (pistillate flowers open at a different time to the pollen-shedding

male flowers, the catkins). In selecting suitable pollinators it is essential to have this overlap otherwise little or no cross pollination will occur. It should be noted also that there is frequently a predominence of one sex on a plant. A suggested ratio of pollinators is 1:8.

On some of the apple trees in my garden there is a cotton wool-like sticky substance growing. It has just formed on the trees and last season It damaged a lot of the fruit. Could you advise what it may be and how to control it? M.L. (Chch). It would seem highly likely that the problem referred to is caused by the presence of woolly aphids although it is more probable that the fruit has been affected by something else. Control of woolly aphids is necessary as build up of infestation will lead to bud destruction and gradual debility of the tree. Despite the widespread presence of a natural predator, a tiny Chalcid fly, this pest seems to be on the increase in home gardens. Swabbing colonies with methylated spirits during the year is effective and so is the application of spraying oil plus lindane at any time between dormancy and greep tip.

Gardeners* Queries should be sent directly to Mr Mike Lusty, 56 Wayside Avenue, Christchurch 5. Samples should be separately wrapped in a plastic bag with air holes. Provide representative, good-sized samples, and your name and address. A nom-de-plume can be used for publication.