Gardener’s queries

Press, 30 December 1985, Page 12

Gardener’s queries

GARDENING

by

M.Lusty

The enclosed carrots are turning yellow and dying off. I would appreciate advice about the trouble. !. ,!. (Chch). The yellowing and dying of the carrots can be caused by two unrelated pathogens. Aphids transmit a virus and when their infestation is severe the effects can almost wipe out an immature crop of carrots. Root rot, as evidenced on one of the intact roots, can be even more devastating in is effect. The latter is associated with poor drainage, over watering and poor air movement between plants. Aphids are at their most prevalent until about this time of the year and generally infestations have been particularly heavy this season. Apart from sowing more resistant varieties such as Taranaki Strongtop, periodic spraying is advocated. Could you please give some reason why my clematis plants are dying off. They have been growing in the same position for many years. Two others have died and one I saved last year by shifting it They start off the season with healthy growth and then slowly start to brown off from the bottom, the young shoots dying right off. A once-healthy. azalea nearby has died also. There are native trees growing about ten feet away. K. E. (West Coast). It can only be surmised that the problem emanates from the root zone. It is possible that impeded drainage, to which clematis is very susceptible, has caused root rot, which generally shows up in the stems and foliage first An indication of this trouble can be obtained by examining the roots which, if affected, will display a brown, water-soaked appearance instead of -being light in colour and freft to look at. “

Enclosed are samples of petunias which have gone the same way for three years running now, despite replacement of the soil and the addition of compost. The second specimen is of oxalis found growing in a new garden area. Is it the one that is so hard to eradicate? Also enclosed is a specimen leaf from an asian pear which looks to have a deficiency. Your comments would be appreciated. A. T. (Chch). The yellowing of the leaf margins of the asian pear may be a nutrient deficiency, possibly potassium, as can sometimes happen under, very dry conditions; or maybe herbicide damage. The petunias are suffering from a root rot Possible contributory factors in this respect are too deep plant-

ing, over-watering and poor drainage. The oxalis is Oxalis articulata, commonly known as sourgrass which has a rbizomatous rootstock. Although not nearly as persistent and troublesome as the bulb-producing species, it would be advisable not to foster it I have a hothouse covered with semi clear durolite. When I grow tomatoes the leaves become very dark green in colour and the growth tends to be restricted. Bunching of the leaves occurs as well. The pH of the soil is O.K. and it was treated with basamid last win* ter. The problem has persisted for two years now. R. F. (Chch). It is regretted but it has not beentf possible to make more suggestions as to the cause of

the problem, it could be that herbicidal residues are being carried over in the soil from the basamid treatment. Contamination could have been introduced through straw, lawn clippiings or even animal manure. If insufficient light was a factor the plants would be etiolated, that is, drawn and pale in colour. Can you identify the plant enclosed? It has pink flowers which when pinched resemble a policeman's helmet, hence the name quoted to us by the person who gave us the plant. Other authorities say it could be “Himalayan Balsam” or “Monk’s Hood”. I have many gardening books but the information I want always seems to be in another one. The active brain is certainly the handiest computer. I. M. (Chch). i The plant is one of the hybrid forms of Impatiens, widely known as busy lizzies. Policeman’s helmet is an unknown reference and its origin has not been traced in consulted references. Monk’s hood is the name given to Aconitum, ajjenus of herbaceous perenni-

Wind is a major agent in the distribution of seed. To aid this form of dispersion, various appendages are formed on the seed. The cotton wool-like deposits in the vicinity of Populus deltoides, as seen above caught up in lank grasses are

noticeable now. Other aids to wind dispersion of seed include the feathery development of the styles in Clematis, winged capsules of Dodonaea, the pappus as in dandelions and thistles, and the winged samaras of Maples.