DAMPING OFF: A fungus, usually affecting seedlings and causes the stem to rot off at soil level. The result of soil borne diseases and over watering. Sterilized potting soil and careful sanitation practices usually prevent this.
DAPPLED SHADE: High shade that is created by allowing sun to shine through.
DARK-DEPENDENT SEEDS: Seeds that germinate only in darkness. So, must be covered with soil.
DAY LENGTH: This merely is the number of hours from sunrise to sunset. Sometimes used interchangeably with photo period.
DAY NEUTRAL: A plant whose blooming period is not affected by the length of day.
DEAD-HEADING: The removal of faded heads of flowers. Pinch here, snip there, removing spent flowers that have already bloomed. This process of pinching off used or spent blooms is to keep the plants well groomed and to prevent them from setting seed. This will also promote continued bloom.
DECIDUOUS: plants that drop their leaves at the end of each growing season.
DETHATCH: Process of removing dead stems that build up beneath lawn grasses.
DIBBLE: A pointed tool used to make holes in the soil for seeds, bulbs, or young plants.
DIEBACK: This condition is water, nutrient, disease, insect, or pruner inflicted in the area where part of the plant is dying.
DIOCECIOUS: A plant which bears either male or female flowers.
DIRECT SEEDING: putting the seed directly in the soil as opposed to transplanting seedlings.
DISBUDDING: In reference to fruit crops, by selectively taking off buds to diminish the crop production and to have quality over quantity.
DISC (DISK): The flat central part of a compound flower. It is made up of short, tubular florets.
DITHER: Just a plain old utensil of any kind to make a hole in the ground to drop a seed into.
DISTILLED WATER: Pure water free from dissolved salts. Formerly made by distillation, now produced chemically by demineralisation.
DIVIDING: The process of splitting up plants, roots and all that have began to get bound together. This will make several plants from one plant, and usually should be done to mature perennials every 3 to 4 years.
DIVISION: a method of propagation by separating and planting segments capable of growing roots and shoots.
DOLOMITIC LIMESTONE: Sometimes used when 'liming' soil that has an acid pH level that is too high. As it contains calcium and magnesium carbonate it should be used only with soils that are also deficient in magnesium as well. See Calcitic Limestone.
DORMANCY: The yearly cycle in a plants life when growth slows and the plant rests. Fertilizing should be withheld when a plant is in dormancy.
DORMANT PERIOD (DORMANCY): The time when a plant has naturally stopped growing and the leaves have fallen or the top growth has died down. The dormant period is usually, but not always, in winter. Compare resting period.
DOUBLE DIGGING: a method of digging a garden bed which involves removing the soil to the depth of one spade blade and then digging down an equal distance, breaking up and mixing the soil.
DOUBLE FLOWER: The Latin name for this is "flore pleno." It refers to flowers that have many petals present, such as roses.
DOUBLE POTTING: A term for placing a potted plant in a larger pot with damp peat moss surrounding it.
DOWNY MILDEW: A certain kind of mildew caused by a special fungi. Often confused with sooty mildew and powdery mildew. As with all mildews it is a problem in hot and humid weather. And, like many fungi it transports its spores. The plants affected will have fuzzy patches on the leaves.
DRAINAGE: Term used to describe how water moves through the soil. All soils should have good drainage as pooled water can cause fungus and bacterial problems, and rot.
DRIFT: when a pesticide is blown by wind onto nontarget organisms.
DWARF: Shorter than its normal growth. Each family of plants has a height recommendation for dwarfness.
DRAWN: Excessively tall and weak growth, caused by plants being grown in too little light or too closely together.
DRILL: A shallow furrow into which seed is sown.
DRIP IRRIGATION: A trickle irrigation system. Highly recommended for soaking the soil well. Used where water sources are limited.
DRIP LINE: a line encircling a tree corresponding to the furthest extension of the branches of a tree.
DRUPE: A fleshy fruit, such as a peach, plum, or cherry, usually having a single hard stone that encloses a seed.