Another cause of disappointment is a prolonged delay before the onset of flowering; the usual reason here is a failure to harden off the plants properly before planting out. A third reason for disappointment is a flowering period which is abnormally short. The two major culprits here are a failure to deadhead spent blooms regularly and an intolerance of the plant to prolonged hot weather.
An important pest of Chrysanthemum and Dahlia which may also attack Pansies, Zinnia and Larkspur. At night the petals are eaten, making them ragged and unsightly. During the day the earwigs hide in the heart of the blooms or beneath leaves and in other debris on the ground. Clear away rubbish. Shake open blooms and if the attack is serious you should spray plants and soil thoroughly with permethrin.
Grey Mould (Botrytis)
Grey mould is a serious disease of plants which strikes when the weather is humid. It can attack a wide variety of blooms, Chrysanthemum, Dahlia, Myosotis, Pelargonium, Zinnia, African Marigolds, Helianthus etc. Flowers may be spotted at first, but later rot and become covered with a fluffy mould. Badly diseased buds fail to open. Pick off mouldy leaves and flowers as soon as they are seen. Spray with a systemic fungicide.
This is a common problem with Sweet Peas. Attack by sparrows is sometimes the cause but the usual culprit is a sudden change in temperature or in the water content of the soil. Try to avoid stress conditions, add more organic matter to the soil when growing Sweet Peas next year.
These active, sap-sucking bugs are a serious pest of Dahlias, Chrysanthemums, Salvias and many other plants. Small ragged holes with brown edges are formed in the leaves, the foliage may be killed, and if they open the flowers are lop-sided. Spraying is rarely necessary, if it is a problem then use an insecticide and repeat two or three times at fourteen day intervals.
Petals sometimes possess streaks or patches of an abnormal colour. A virus causes this colour break and there is no cure. This effect may occur in Dahlia, Chrysanthemum, Viola and Wallflower.
The effect is sometimes attractive but in a single-colour bed it is undesirable.
Aphids, both greenfly and blackfly, can seriously reduce the quantity and quality of the floral display. When the weather is warm and dry, large colonies of these pests build up on the buds of many plants, causing the flowers when they are open to be undersized. In a severe attack the buds may fail to open. Spray with a contact or systemic insecticide when the pests are first seen.
Birds are extremely selective in their choice of flowers. Most blooms are ignored but Polyanthus is sometimes severely attacked in winter or spring. The yellow varieties may be completely stripped of buds and flowers by sparrows and blackbirds. Sweet Peas are sometimes attacked later in the year. Surprisingly, plants in one garden may be ruined and similar plants next door may be spared. Control is difficult, netting is unsightly and repellants are rarely effective.