Gardeners’ queries

Press, 15 May 1987, Page 14

Gardeners’ queries

Enclosed are some shrivelled leaves and twigs from our apricot tree. Please advise whether it should be pruned hard, or if it needs some other treatment? It had a reasonable crop, but a lot of the fruit went brown and mouldy. There are lots of gummy extrusions on the tree. Our walnut tree, which is probably very old, has had hardly any fruit this year. Usually it provides well for us and the oppossums, which come at just the right time each year. S.P. (Lyttelton). Weather was poor when walnut flowers were receptive to pollination and this would account for the generally light crops this year. Several diseases can cause exudation of gum from the branches of apricot trees, including brown rot. This fungal infection is probably responsible in this case, and is a constant threat where ever stone fruit is grown. The disease can spread very rapidly under conditions favourable — periods of warm, damp weather — but can occur at closer to harvest. Brown rot over-winters on mummified fruit and cankered wood. Control should consist of a thorough, pre-leaf fall spray with Bordeaux mix-

ture followed by the removal of all diseased fruit remaining on the tree or lying on the ground. Cankered and dead wood should be pruned hard back and all exposed surfaces treated with an appropriate sealant. At bud movement and again 7 to 10 days later repeat spray with either Bordeaux mixture (reduced strength the second time) or any other copperbased material.

I would be grateful if you could identify the enclosed apple, which comes from a very old tree and is a rather small specimen. Also, what is the climbing plant which has a strange root rather like a spiky fir cone? Thank you for your help and informative answers to queries. F.B. (Sumner).

Unless the apple has a very pronounced characteristic it is essential to provide at least two dr three typical specimens to facilitate identification as there so many that even small variation can increase the difficulties in naming. Unfortunately this applies here. The climbing plant is known as smilax, Asparagus asparagoides, a species of asparagus.

Can you please answer the

GARDENING

by 1

Mike Lusty

following: (1) Do greengages come true from seed or is it best to buy them? (2) Is a pollinator essential or just desirable? (3) Will Japanese plums act as pollinators? (4) Will single ornamental European plums act as pollinators? D.F. (Rangiora). Variability is to be expected from greengages which are raised from seed; they require a cross pollinator as they are self-sterile. Suitable cross pollinators for the greengage include Angelina Burdett, Coe’s Golden Drop, Blue Diamond and Grand Duke. Japanese plums do not seem to be capable of fertilising European ones, but a few of the latter will apparently fertilise at least some of the Japanese plums. Some of

the single flowering, ornamental European plums may be effective for cross-pollinat-ing some of the fruiting varieties, but this would be open to experimentation. Enclosed is a sample of grapefruit tree which was about 25 years old. After a wet winter it still looked O.K. About six weeks ago it started to look seedy, and has since died. I gave it a watering with Epsom salts, but it never responded. Could the trouble spread to a healtby orange and a lemon tree in the same area? R.S. (Akaroa). There was no discernible evidence on the specimen to show how the grapefruit died. Citrus are very susceptible to root infection, which takes some time to show up on the above ground structure of the plant, but when it does it is usually too late to control it. Prolonged periods of submersion in water and poor drainage are conducive to this problem. Epsom salts is a source of magnesium sulphate and is applied where there is a deficiency of magnesium, not uncommon where citrus are grown. Gardeners* Queries should be sent directly to Mr Mike

Lusty, 51 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.