Our ‘A’ to ‘Z’ of Gardening Terms

Terms that begin with “D”

damping-offA disease caused by many different organisms. In the most conspicuous cases, a seedling’s stem collapses at or near the soil surface, and the seedling topples. Another type rots seedlings before they emerge from the soil or causes seeds to decay before germinating.
day-neutral plantA species capable of flowering without regard to day length. See short-day plant, long-day plant.
deadheadTo remove individual, spent flowers from a plant for the purpose of preventing senescence (going dormant) and prolonging blooming. For effective results, the ovary behind the flower must be removed as well.
deciduousA plant that sheds all of its leaves annually.
decompositionThe breakdown of organic materials by microorganisms.
defoliationThe unnatural loss of a plant’s leaves, generally to the detriment of its health. Can be caused by high winds, excessive heat, drought, frost, chemicals, insects, or disease.
dehorningA drastic method of pruning a neglected tree or shrub. Entails the removal of large branches, especially high in the crown, a few at a time over several seasons.
dermapteraAn insect family made up of species having chewing mouthparts and a pair of large, forceps-like appendages near the tail. Wingless or with one or two pairs of inconspicuous wings. Earwigs are an example.
desiccationDrying out of tissue.
determinateA plant growth habit in which the stems stop growing at a certain height and produce a flower cluster at the tip. Determinate tomatoes, for example, are short, early-fruiting, have concentrated fruit set, and do not require staking. See indeterminate.
dethatchTo remove thatch (a tightly intermingled layer of stems, leaves, and roots, living and dead, that forms between the soil surface and green vegetation of grass).
diageotropicHorizontal growth of a plant part.
diatomaceous earthThe fossilized remains of diatoms (a type of tiny algae).
dicotA plant having two cotyledons (seed leaves).
dicotyledonSee dicot (above)
diebackProgressive death of shoots, branches, or roots, generally starting at the tips
differentiationA change in composition, structure, or function of cells and tissues during growth.
dioeciousA plant species having male and female flowers on separate plants. An example is holly. See monoecious.
disbudThe selective removal of some flower buds so the remaining buds receive more of the plant’s energy and produce larger, showier flowers. Roses, chrysanthemums, and camellias often are disbudded.
disc flowerA small, tubular flower in the center of a composite head.
divisionThe breaking or cutting apart of a plant’s crown for the purpose of producing additional plants, all genetically identical to the parent plant.
DNADeoxyribonucleic acid. The substance that the genes which carry genetic information is made of.
dominate speciesThe most abundant species in a plant community.
dormancyThe annual period when a plant’s growth processes greatly slow down.
dormant budA bud formed during a growing season that remains at rest during the following winter or dry season. If it does not expand during the following growing season, it is termed a latent bud.
dormant oilA horticultural oil applied during the dormant season to control insect pests and diseases.
double, semidoubleA flower with more than the normal number of petals, sepals, bracts, or florets. May be designated botanically by the terms flore pleno, plena, or pleniflora.
double workedGrafted twice, i.e., grafted to an intermediate stock.
drainageThe ability of soil to transmit water through the surface and subsoil.
drip tipA pointed leaf tip helping to drain water from the leaf surface.
drip zoneThe area from the trunk of a tree or shrub to the edge of its canopy. Most, but not all, of a plant’s feeder roots are located within this area.
driplineAn imaginary line on the ground directly beneath the outermost tips of a plant’s foliage. Rain tends to drip from leaves onto this line.
drupe fruitSee stone fruit.
dwarfedRestricted plant size without loss of health and vigor.