DEAD-HEADING The practice of removing dead flower heads. This serves two purposes — to tidy up the plant and to encourage the production of further flowers.
DECIDUOUS Plants that lose all their leaves once a year, usually in winter.
DISEASE: A plant illness not directly caused by pests. Usual causes of disease amongst plants are fungi, bacteria and viruses.
DISORDER: A plant malfunction not caused by pests or disease. Unsuitable growing conditions, bad cultivation and soil deficiencies are all responsible for plant disorders.
DIVIDE: To split a plant into several sections, each having its own portion of roots, for propagation purposes.
DORMANT: When a plant is in a state of rest. In plants, growth and other functions are much reduced and in a deciduous plant the leaves fall off. Dormancy usually occurs in winter and is the best time to transplant as a plant is less likely to sustain a shock to the system while at its least active.
DRESSING: A substance supplying plant foods applied dry to a soil. Top dressings are added to the surface, base dressings are incorporated into the soil when digging.
DRILL: A channel made in soil into which seeds are sown, and then covered up. Also an appliance for sowing seeds.
DUST: A pest or disease control applied to a plant or the soil as a fine, dry dust as opposed to a liquid spray.
DWARF: A plant of naturally small and slow-growing habit.