Plant Science Terms - D

Damping off - death of seedlings, from failed seed emergence or falling over after emergence from the soil due to stem rot near the soil surface

Dappled Shade - areas where there is a mixture of sun and shade, generally because a deciduous tree is nearby. Dappled shade is similar to partial shade

Day-neutral plant - a cultivar or species capable of flowering without regard to day length. (See also Short-day plant, Long-day plant.)

Deadhead - to remove individual, spent flowers and seed heads from a plant for the purpose of preventing senescence and prolonging blooming. For effective results, the ovary behind the flower must be removed as well

Deciduous - trees or plants that shed their leaves each year (annually) during one season usually the fall and winter

Decomposers - microorganisms and invertebrates that accomplish composting

Decomposition - breakdown of organic materials by microorganisms

Deer Resistant Plants - plants that deer are less likely to nibble on.  Hungry deer (or rabbits, ground hogs, squirrels etc...) will, however, eat almost anything if they are hungry.  Deer tastes also vary by region so trial and error may be necessary to choose deer resistant plants for your area

Defoliation - unnatural loss of a plant’s leaves, generally to the detriment of its health. Can be caused by several factors such as high wind, excessive heat, drought, frost, chemicals, insects, or disease

Dehiscent - type of dry fruit in which the carpel (a simple pistil) splits along definite seams at maturity

Dehorning - 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

Dentate - having large blunt teeth ending in an acute angle, pointing outward

Deoxyribonucleic acid (DNA) - is the genetic information that dictates all cellular processes. DNA is organized into chromosomes and is responsible for all characteristics of the plant

Depredation - causing damage or loss

Dermaptera - major order of insects that have two pairs of wings, or are wingless, and have mouthparts (earwigs)

Desiccation - excessive dryness or loss of moisture resulting in drying out the plant tissues

Determinate - plant growth habit in which 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 may not require staking. (See also Indeterminate)

Determinate growth - limited growth

Determinate inflorescence - in determinate inflorescences, the youngest flowers are at the bottom of an elongated axis or on the outside of a truncated axis. A terminal bud forms a terminal flower and then dies out, stopping the growth of the axis. The other flowers then grow from lateral buds below it

Dethatch - to remove thatch (a tightly intermingled layer of stems and roots, living and dead, that forms between the soil surface and green vegetation of grass)

Devigorating - opposite of invigorating- to give vigor to, fill with life and energy, energize

Diatomaceous earth - fossilized remains of diatoms (a type of tiny algae) used to kill insect pests, snails, and slugs

Dichotomous key - tool that allows the user to determine the identity of items in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish. Keys consist of a series of choices that lead the user to the correct name of a given item

Dicot - having two cotyledons in the seed. See Dicotyledon

Dicotyledon - plants with two seed leaves. Also referred to as dicot

Dieback - progressive death of shoots, branches, or roots, generally starting at the tips

Differentiation - change in composition, structure, and function of cells and tissues during growth

Dioecious - plant species that have male and female flowers occurring on separate plants (e.g., holly)

Diptera - major order of insects that have one pair of wings and sucking or siphoning mouthparts as adults and chewing mouthparts as larvae (mosquitoes, flies, and gnats)

Direct seeding (direct sowing) - planting seeds into garden soil rather than using transplants

Disbud - selective removal of vegetative or flower buds so that the remaining buds receive more of the plant’s energy and produce larger, showier flowers. Roses, chrysanthemums, and camellias often are disbudded        

Diseased plant - plant that is abnormal because of a disease-causing organism or virus

Distorted growth- twisted or misformed growth

Diurnal - active during the day

Division - breaking or cutting apart of a plant’s crown for the purpose of producing additional plants, all genetically identical to the parent plant

Dodder - parasitic plant with yellow to orange stringlike stems and inconspicuous flowers

Dormancy - an annual period which causes the resting stage of a plant or ripe seeds during which nearly all manifestations of life come to an almost complete standstill

Dormant - state of suspended growth (cellular activity) due to resting or not growing or the lack of outwardly visible activity caused by environmental or internal factors


Dormant bud - 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 latent

Dormant oil - an oil applied during the dormant season to control insect pests and diseases

Double, semidouble - a 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 worked - grafted twice, i.e., grafted to an intermediate stock

Downy - leaf surfaces covered with very short, weak, and soft hairs

Downy mildew - group of diseases characterized by white, bluish, or gray sporulation on the underside of leaves caused by the oomycete. This obligate parasite seeks out vascular plants, because it cannot survive outside of a living host. It does not produce overwintering oospores, but survives from year to year on living plants. These organisms are distinctly different from the powdery mildews

Drainage - ability of soil to transmit water through the surface and subsoil

Drain tile system - tiles installed in the ground acts as a piping system to collect and redirect subsurface water that moves down into and through the soil

Drip irrigation - application of small quantities of water directly to the root zone through various types of delivery systems on a daily basis

Drip line - an imaginary line on the ground directly beneath the outermost tips of a plant’s foliage. Rain tends to drip from leaves onto this line

Drip zone - 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

Drought Avoidance - plants that have developed storage capacity or other characteristics that enable them to weather severe drought without wilting, such as cacti, succulents etc.

Drought Resistant - plants that can withstand periods with little to no supplemental water when planted and established in the landscape.  No plant in a pot is truly drought resistant, they will all need some water.  All plants will need to be watered while getting established.  Annuals and perennials need 2 to 3 weeks to establish, shrubs and trees need a year to become established.  Often used interchangeably with drought tolerant although their definitions are different

Drought Tolerant - plants that deal with severe drought on a regular basis, and recovers from repeated wilting.  All plants will need to be watered while getting established.  Annuals and perennials need 2 to 3 weeks to establish, shrubs and trees need a year to become established.  Often used interchangeably with drought resistant although their definitions are different

Drupe fruit - type of fruit with a thin outer skin-like region, a center portion that is thick and fleshy, and an inner area that is hard and stony. See stone fruit

Dry - water only when the soil is quite dry.  Plants that prefer dry conditions may be susceptible to root rot disease if kept too wet.  Dry plants will need little to no supplemental water once established if they are planted in the ground

Dry to Normal - water when the top of the soil in a pot is dry to the touch but err on the side of dry rather than wet.  While these plants will be more tolerant of moist conditions than Dry plants they still do not like constantly moist soil.  Dry to Normal plants will need little to no supplemental water once established if they are planted in the ground

Dwarfed - restricted plant size without loss of health and vigor


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