Florence Grovida Gardening

Diseases

• How To Create A Biodome Greenhouse

Domping-o//. This disease is caused by several different soil and water-borne fungi which cause the collapse of seedlings at ground level. It is most troublesome where seedlings are overcrowded, overwatered, or grown in unsterilized compost or watered with water from a dirty tank or butt. Prevent infection therefore, by sowing seeds in sterilized compost and by watering carefully with clean water,

Foot rot, Crown rot and Root rot. May be caused by the same fungi as those causing damping-off and also by others. These organisms cause a brawn or black rot of the tissues at the base of the stems, around the crowns or at the roots resulting in wilting or collapse of the top growth. Use sterilized compost and pots and clean water to prevent infection. It is sometimes possible to save a diseased plant by watering with a solution of cheshunt compound or zineb.

Grey mould (Botrytis cinerea). This fungus causes rotting of leaves, stems and flowers, the affected tissues becoming covered with a grey-brown mass of fungal spores. In less severe cases small red or brown spots develop on petals. The disease is most troublesome in greenhouses where the humidity is high and hygiene is poor. Prevent infection by the prompt removal and burning of all diseased or dying parts. Ventilate well to reduce the humidity and water early in the morning and not at night. Fumigate with tecnazene smokes, or spray with captan, carben-dazim, benomyl or thiophanate-methyl at the first signs of the disease.

Powdery mildew. This type of disease shows as a white powdery coating on the leaves and sometimes the flowers and the stems of chrysanthemums, begonias, cinerarias and occasionally other plants. As the fungi are encouraged by humid atmospheres ventilate the greenhouse well. Plants that are dry at the roots are more susceptible to infection so water before the compost dries out completely. Remove severely affected leaves and spray with benomyl, carbendazim, dinocap, propiconazole, pyrazophos, thiophanate-methyl or triforine.

diseases

1. The rusts of fuchsias and cineraria show as orange powdery pustules on the lower leaf surfaces, but on chrysanthemums, pelargoniums and carnations the pustules produce masses of chocolate-coloured spores. Remove and burn affected leaves and in severe cases destroy the whole plant. Ventilate the greenhouse well to reduce the humidity, and when watering, make sure that droplets do not remain on the leaves. Spray at seven to ten-day intervals with mancozeb or zineb.
2. Cucumber mosaic and other viruses can affect a wide range of plants causing mottling, blotching or striping of the leaves, the affected parts being pale green, yellow or black. The leaves may also be distorted and the plants stunted. Destroy any plant showing these symptoms. Control aphids by suitable spraying as these pests transmit some viruses including cucumber mosaic.

Physiological disorders. These are due to unsuitable cultural conditions and are very common on greenhouse plants. The commonest disorder is called Oedema and in this the plant shows pale pimple-like outgrowths on the undersurface of the leaves and on the stems. Later they burst and become brown and powdery or corky. Ivy-leaved pelargoniums are particularly susceptible to this trouble which is due to overwatering and/or too humid an atmosphere. Improve the cultural conditions by careful watering and ventilation. Do not remove affected leaves.

Bud drop. The dropping or withering of buds is usually due to drying out of the compost at a critical stage of growth. Do not allow the compost to dry out when flower buds are just begi nning to develop.

Corky scab of cacti shows as irregular rusty or corky spots which develop into sunken patches. This is due to lack of light and too high humidity or by over-exposure to sunlight. Where the trouble is very unsightly propagate from the affected plant and give the new plants correct cultural treatment.

As temperatures fall in the autumn it becomes especially important to remove dead flowers and foliage and to avoid a damp and stuffy atmosphere. Moulds develop most easily on decayed vegetation, but flowers and soft growth may be spoiled by the dreaded grey mould (see above) if there is not heat or ventilation to keep the air moving.

Freesias are valued For their beautiful spring flowers and their sweet scenl.

For those who do not use a greenhouse in winter this is the time to take out and burn all those plant remains, while the rest of us make the hard decisions as to what to save and what to propagate for another year. By late September we need to be ready for a hard frost with all tender plants under cover, the heating system tested, and fuel in store. For the real greenhouse enthusiast there are flowers for every season and the warmer the greenhouse the earlier our spring.