GARDENING

Press, 21 July 1989, Page 11

GARDENING

by

Mike Lusty

Enclosed are some tubers which I have recently dug up from my garden. Most of them seem to have a sort of blistered appearance which, however, does not seem to affect them inside too much. Is it likely to become more serious in the years to come, and what can be done about it? H. R. (Kaikoura). The brownish protuberances and blistered skin on these tubers is due to the presence of common scab. This is considered to be more of a physiological problem rather than a disease, and tends to manifest itself more in alkaline soils, especially under dry conditions. It can be introduced to an area by planting infected seed potatoes following which it can become soil borne. Crop rotaton the avoidance of lime, a slightly acid medium, and an adequate soil . moisture presence following planting will control the incidence of common scab. Enclosed are bark samples from my trees and I would be obliged if you could advise me how to deal with this debarking problem. The trees are approximately 30 years old, and have had a good crop of apples. The younger branches are healthy, but the trunks and oljler wood are not. M. P. (Chch).

Flaking bark on the trunks of apple trees is an almost characteristic symptom of these threes as they age. The development is more pronounced with some varieties than others, it does not appear to impair the health or productivity of the tree, and cannot be controlled. Decay, in which the wood rots, is something different again and may be due to one or various factors. Sometimes it is possible to arrest further deterioration in this respect by removing all the rotted wood and filling the cavity thus created with concrete. Very old trees have been noted to survive and fruit despite having only a shell for a trunk. L . I enclose a photograph of an interesting plant that has appeared in a newly cleared area of my garden. It grows like a nightshade, but much taller and has some hairs growing from

the leaves. Could you inform me 1) whether it is poisonous, 2) its name 3) whether it could take over my garden. M. E. (Hawarden).

The plant depicted in this good clear photograph is of Nicandra physalodes. This is a robust annual, native of Peru and somewhat reminiscent of Physalis. Commonly known as Apple of Peru it is also referred to as Shoo Fly Plant as it is reputed to keep flies away. Growing fairly rapidly to about one metre in height, it forms an attractive plant with its. oak tree- 1 like leaves bell-shaped pale blue flowers, followed by globular fruit encased in bright green and purple calyces. It is not listed as a poisonous plant in New Zealand, although it belongs to a family many of which contain toxic matter. It does not appear to be widely grown, and it is open ■to speculation as to how it came to grow in your garden. It should not prove to be a threat.

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