Don't get flower buds or petals wet. It can cause markings. Flowers which develop at lower temperatures have a tendency to split. Flowers developing at higher temperatures develop faster and tend to have weaker stems. Aphis and Mites can be very serious pests.
Aphids spread virus and cause distorted growth.
Mites cause mottling of the leaves and eventually drying of the foliage. Thrip and caterpillars can also become a problem. For single flowering varieties the flowers are harvested when the bud has opened fully so that the outer petals are at right angles to the stem and the inner petals are still tightly bunched. For spray types harvesting occurs when the top three flowers begin expanding and the lower buds are showing colour. One part of Boric acid in ten parts water will improve the keeping quality of the flowers by up to one week.