- Damping off
- Decay of young seedlings at ground level following fungal attack. Often the result of soil borne diseases and over watering.
- Deadhead
- The removal of spent blossoms; promotes reblooming by preventing seed production.
- Deciduous
- A plant that drops its leaves yearly at the end of the growing season.
- Defoliation
- The loss of a plant's leaves due to an unnatural cause such as wind, drought, early frost, chemicals, insects, or disease.
- Dethatch
- Remove the dead stem build-up beneath lawn grasses.
- Dieback
- Death at the tips of a plant, usually the result of disease or damage.
- Dioecious
- A plant having unisexual flowers, with each sex on a different plant.
- Disbudding
- The pinching off of selected buds to benefit those left to grow.
- Division
- Removal of part of a plant with roots in order to produce another plant.
- Dormancy
- The temporary slowing or stopping of growth, usually during winter.The rest period of a plant during which it is not growing or showing signs of life. Also refers to seeds before they sprout.
- Drawn
- Excessively tall and weak growth, caused by plants being grown in too little light or too closely together.
- Dripline
- The circular area under a tree from the trunk to the outside tips of the branches.
