Join thousands of gardeners across the UK who use our free service to buy, sell and swap plants ... and much more.

Glossary of plant terms

Search our dictionary of 3,300 botanical and plant-related terms – the largest online.
Or browse the descriptions and definitions using the A-Z.

Daedaleopsis confragosa

Fungus attacks deciduous trees caused white rot.

dahlia smut

Browny-yellow raised spots develop on leaves in mid summer killing them.

Dalapon

A translocated selective weed-killer which will kill grass, reeds, sedges and other monocotyledons but it is much less toxic to dicotyledons. It is particularly useful for killing grass in orchards and around bush fruits. It should not be used near apple trees in winter, and sensitive plants should not be planted on treated ground under six weeks.

damping down

Refers to the wetting of floors and benches in greenhouses to increase the humidity and moderate temperatures. This may be done on hot days when the heat is building up due to the greenhouse effect, when humidity levels are low and when there is insufficient ventilation to ensure cool, moist air.

damping off

The wilting and death of seedlings from infection by a fungal disease which can be soil-borne. Although the plants may initially look healthy, they then rapidly fall over and die. They may be protected by applying a fungicidal drench.

Darwinism

A scientific theory named after Charles Darwin (1809-1882), who was a British naturalist. He studied differences in living organisms and proposed the concept of evolution by natural selection, which gave rise to separate species. This theory was proposed in his book entitled "The Origin of Species".

daylength

This refers to the hours of daylight or artificial light received by the plants affecting the plant growth. Short-day plants only grow, flower and seed if they receive fewer than 12 hours of light per day (ie long periods of darkness). Long-day plants only grow, flower and seed if they receive more than 12 hours of light per day.

day neutral

This refers to plants which will produce flowers unaffected by the daylength.

Dazomet

An organic chemical which is used to part-sterilise the soil to combat eelworms, but it is toxic to mammals and needs to be used carefully.

DDT insecticide

DDT stands for dichlorodiphenyltrichloroethane. It was used widely as an insecticide, but has become generally ineffective now since insects have become resistant, and it has accumulated in the food chain such that fish, birds and humans all now have unhealthy quantities in their bodies. Biological control and better cultivation techniques are preferred methods where possible of controlling pests.

dead-heading

The practice of removing faded flowerheads in order to prevent seeding, to encourage further flowering, stop die-back into the stems or to keep a plant looking tidy. Annual plants can have regular dead-heading to prolong their display, and fading flowers can be removed from roses and other plants to encourage to opening of further blooms.

debilis

Means "weak" in Latin.

decaploid

Having 10 sets of chromosomes.

deciduous

A plant which sheds its leaves at intervals. In the temperate regions, leaves are shed at the end of the growing season (usually in autumn). New leaves are grown in the next growing season. Semi-deciduous plants lose only some leaves. The majority of deciduous specimens are broad-leaved, and only a few conifers lose their needle-like leaves at the end of the season.

decompose

The breaking down of organic matter such as plant leaves etc, to release carbon dioxide gas and minerals and other inorganic compounds mainly by the actions of fungi and bacteria. Decomposition is a necessary part of the carbon cycle, and recycles nutrients for use by other organisms.

decorative

This term can be used as an alternative to ornamental, but the term decorative may be used as a common name to refer to particular groups of plant species eg the decorative group of chrysanthemums.

decorus

Means "handsome" in Latin.

decumbant

Referring to a shoot, which either initially, or soon becomes prostrate, hanging or declining usually with the tip ascending.

decurrent

When the blade or stalk of the leaf continues, as a rib, down the side of the stem.

decurvus

Means "curved downwards" in Latin.

decussate

Arranged in opposite pairs, alternate pairs being at right angles to each other.

deep-bed system

This is a bed created by deep digging, incorporation of manure and piling up of the soil for the cultivation of vegetables. Such a bed is usually under 2 metres wide and is not walked on to avoid compaction. Since the soil condition is so good, crops are usually planted more densely.

deepest roots

A Wild Fig tree in South Africa has had its roots measured to a depth of 120 metres (400 feet).

deer

May cause the leaves or bark of a range of plants to be gnawed away.

deficiency

This refers to a condition in the plant or soil where certain nutrients are lacking. Examples of diagnostic symptoms for deficiencies in brassicas can be: boron deficiency gives rise convex cupping of leaves, iron deficiency gives rise to young leaves turning yellow, and manganese deficiency gives rise to interveinal chlorosis in the leaves.

defoliate

The action of stripping the leaves from a plant, possibly by pests or disease, or by cultivation, or by a seasonal leaf fall.

degrees C

A measure of temperature (C) where the freezing point of water is OC (or 32F), and the boiling point is 100C (or 212F).

degrees F

A measure of temperature (F) where the freezing point of water is 32F (or 0C), and the boiling point is 212F (or 100C).

dehiscent

Splitting; particularly of fruits and sporangia, to allow the seeds of fruits or the spores of sporangia to escape.

delicatus

Means "charming" in Latin.

deliquescent

A term meaning that part of a plant is split up into many branches.

Delphinium black blotch

Black blotches develop on leaves which then can spread to petioles and flower buds. Severely affected leaves may wither.

Delphinium leaf miner

Leaves develop large, brown, dried up areas. White maggots feed within mined areas.

Delphinium moth

During spring, leaves are spun together with silk thread by green caterpillars.

Delphinium viruses

Yellowing of foliage as a mosaic pattern. Plants fail to grow properly.

Deltamethrin

A contact insecticide often used on ants and some other insects.

deltoid

In a triangular shape, usually referring to leaves.

demissus

Means "hanging down" in Latin.

demursus

Means "living under water" in Latin.

denitrification

Refers to the conversion of nitrates in the soil or water to nitrites and nitrogen gas by the action of organisms, especially by the action of denitrifying bacteria under anaerobic conditions. This process makes nitrogen unavailable to other organisms, and is part of the nitrogen cycle which maintains the balance of nitrogen in the environment.

dentate

With toothed margins.

dentatus

Means "toothed" in Latin.

denticulate

Minutely dentate; having small tooth-shapes around the margin.

denticulatus

Means "finely toothed" in Latin.

denudatus

Means "stripped bare" in Latin.

depressed

Flattened from above.

derris

This is a chemical (containing rotenone) derived from plants, which is used as an insecticide; it can be the active ingredient in derris dust.

deserts

Deserts generally have very low rainfall and humidity, with high evaporation rates and little cloud cover. Many deserts are hot but some can be bitterly cold. Desert soils are generally poor because they contain little vegetable matter but if water is supplied, most deserts are capable of sustaining agriculture. The Sahara Desert in Africa is the world's largest dry desert. Any living plant or animal that makes its home in the desert has to adapt to some of the harshest conditions imaginable. Plants have to endure long periods of drought and often dramatic variations in temperature. Some desert trees are extremely deep rooting, allowing them to reach underground water sources. Many plants either store water, like many cacti and succulents, or lie dormant until the rains come, like sagebrush. Semi-dry deserts do have some seasonal rainfall, such as the sub-Saharan region in Africa or the outer regions of the Great Sandy Desert in Australia. Desert plants flower only very rarely, when conditions are suitable; within a few hours of rainfall, plants that have not flowered for years burst into bloom, and the desert is a mass of colour for a few days. Pollination of these flowers is usually by insects which can also breed very rapidly following rainfall. . Natural deserts occur when geography and climate combine to prevent significant amounts of rain falling on an area. Continental deserts, such as the Gobi in Mongolia, are too far from the sea and large waters to receive any significant moisture. Coastal deserts, such as the Namib in southern Africa, are formed when cold ocean currents cause local dry air masses to descend. Rain shadow deserts lie in the lee of mountains where the rain falls on the windward slope, as is the case in the Mojave Desert beyond the Sierra Nevada in California. Tropical deserts are caused by the descent of air that is heated over warm land and has previously lost all its moisture. Man-made deserts occur as a result of human mistakes which have degraded dryland areas - through deforestation, overgrazing, poorly designed irrigation systems, and soil erosion.

de-shoot

The act of removing some or all of the shoots of a plant, usually with the intention of channelling energy into a particular shoot or bud.

determinate

Refers to an inflorescence where the top flower opens first, so preventing further stem elongation. The other flowers in the inflorescence open on side branches.

Devonian period

A period of time in the Earth's development 360 to 400 million years ago. First appearance of vascular plants and fern-like plants; members of the classes Lycopsida and Psilopsida. Amphibians evolving.

dew

This is moisture that appears, often in the early morning, on the leaves of grass and other surfaces. Dew is caused by a high water content in the atmosphere which can no longer be held in gaseous form (water vapour) as the air cools (dew point) and therefore condensing on contact with surfaces.

dew point

This is the air temperature that causes dew to appear on the leaves of grass and other surfaces, as the high water content in the atmosphere can no longer be held in gaseous form (water vapour) as the air cools and therefore causes condensation.

diagnosis

Identifying a disease, pest or disorder by the symptoms shown by the plant.

diamond black moth

Pest of Brassicas where the caterpillars eat the leaves resulting in a "skeleton".

Dianthus anther smut

Anthus become swollen and darken as they fill with masses of black-purple spores.

Dianthus fusarium wilt

Flowers fade, leaves wilt and eventually the whole plant dies.

Diazinon

This is an insecticide used mainly to kill aphids, and a wide range of insects. Diazinon is poisonous to humans and other warm-blooded animals, and therefore the manufacturer's instructions must be followed carefully. It should not be used on edible crops.

dibber

This is a pointed stake or tool which is used to make holes in soil or compost for the insertion of tubers, bulbs, seedlings or plantlets.

dicamba

This is can be an active ingredient in many hormone weedkillers.

dichlobenil

A granular weedkiller that can be applied to the soil surface (which must be left undisturbed for a period) to prevent the germination of weed seeds.

Dichlofluanid

A sulphur-based organic fungicide that is used to preventively to control Botrytis and some other fungal diseases, but there must be at least a three week gap before harvesting of edible crops.

dichlorophen

A chemical which can be used to control the growth of moss in lawns.

Dichlorprop

An ingredient of weed control mixes for lawns. It is a selective herbicide, killing broad-leaved weeds but not grasses (although scorching may occur). It should not be used in windy conditions, because of the risk of spray drift damage to other plants. It may be used in herbicide and fertilizer (weed and feed) combinations.

Dichlorvos

An organophosphorus insecticide which is used impregnated in strips for control of insects in greenhouses.

dichotomous

Divided into two equal forks, and often forked again and again.

dichotomous branching

Branching into two equal parts.

Dicofol

An organochlorine chemical ingredient of some fungicides.

dicotyledon

Having 2 cotyledons (the first leaves of the embryo plant). Plants belonging to the class Dicotyledonae generally have leaves with reticulate venation.

Didymella stem rot

Black brown sunken blotches develop. Older leaves turn yellow and rot develop on fruit of tomatoes, aubergines etc.

die-back

Death of the tips of the shoots because of frost or disease. Die-back may also occur when incorrect pruning has resulted in a budless section of stem; in bad cases the shoot may die right back along its length causing the death of the whole plant.

Difenacoum

An ingredient of poisoned baits which may be used to control mice and rats.

differentiation

The process of the development of cells, tissues and organs by which differences arise.

difformis

Means "unusual form" in Latin.

diffuse

Loosely or widely spreading.

diffusion

The process whereby chemicals will move randomly to gradually spread themselves throughout a medium (such as within the cells of protozoa and other simple living organisms). Gases naturally spread themselves out to occupy the space available, and dissolved chemicals in liquid will also spread throughout the liquid gradually by diffusion. (Osmosis is a process where diffusion effectively operates in one direction only across a semi-permeable membrane.)

diffusus

Means "diffuse - spreading" in Latin.

digging

A general term for loosening or turning over the soil to improve the condition of the soil and bury weeds or incorporate manure. Single digging means cultivation to one spade depth, and double or trench digging means cultivation to two spade depths.

digitate

A compound leaf whose leaflets are all attached to the same point. Also used where the leaf is divided into finger-like projections, and where the bases are attached to each other.

digitatus

Means "fingered" in Latin.

Dikegulac

An active ingredient of some growth control treatments, such as those used for reducing the need to cut hedges.

diluter

Refers to a device for mixing water with a concentrated liquid for weedkiller etc, so that a diluted solution of a consistant concentration is produced in the hosepipe.

dimethoate

This may be an active ingredient in some systemic insecticides. It is an organophosphorus compound and at least a week should elapse before the harvesting of edible crops.

dimorphic

Existing in 2 separate forms eg 2 different leaf shapes on the same plant.

Dinocap

This is a fungicide used to control powdery mildews on many plants, particularly roses. It is available mixed with foliar feed as a "complete treatment". It is available mixed with foliar feed as a "complete treatment".

dioecious

Bearing male and female organs (flowers) on separate plants. Pollen therefore needs to be transferred from a male flowering plant to a female flowering plant for pollination to enable fertilization and seed production. (Monoecious plants carry male and female sex organs seperately, but both are on the same plant.)

diploid

Having twice the basic (haploid) number of chromosomes. Most growing and mature plants have diploid numbers of chromosomes in their cells. Pollen and ova (plural of ovule) are haploid cells and enable the sexual reproduction since they fuse to give the diploid plant after pollination and fertilization.

diquat

This is a chemical compound which is used in general purpose, non-selective, non-persistent weedkiller.

dis-bud

Removing or pinching out of surplus buds to promote larger flowers or fruits. The removal of a terminal bud of a stem is usually done to break apical dominance in order to promote side branching, bushy growth or spray flower formation. The removal of axillary buds channels the energy into a single bud or flower.

disease

Damage to a plant resulting from infection by certain bacteria, viruses, fungi or mycoplasmas (collectively called pathogens). Some pathogens may live exclusively on a certain plant, and other pathogens may perform part of their life-cycle on different host plants. Diseases are often contracted as a result of the plant being under some form of stress, whereas healthy well-grown plants are less prone to infection.

disk

Usually refers to the flat round centre of a daisy-like flower; such flowers are generally called composites. The term "disk" also refers to the fleshy part of the receptacle which surrounds or surmounts the ovary.

disk-florets

The tube-like flowers at the centre of the flower heads of some members of the daisy family (Compositae). They are surrounded by larger, petal-like ray-florets.

disorder

Malfunctions of the plant caused by factors such as nutrient deficiencies, pollutants, weather, too high or too low temperatures etc.

dispersal

Refers to the spreading of pollen, seeds or plantlets away from the parent plant for subsequent development. Dispersal may be facilitated by a physical mechanism (such as a dehiscent seed head), or by wind, water or animals.

dispersus

Means "scattered" in Latin.

dissected

Divided into many narrow segments.

distal

The end which is distant from the point of reference (or proximal end). This term may be used to describe cuttings; the distal part of a root or shoot is considered thinner than the proximal part.

distichous

Arranged in 2 vertical ranks, diametrically opposite. Usually this is used to describe leaves that are arranged in 2 parallel ranks on opposite sides of a stem.

distributor

May refer to some sort of equipment designed to spread and apply a solid fertilizer or other solid chemical onto the ground.

ditch

General term referring to a long excavation to allow drainage or to act as a boundary.

diurnal

Refers to the duration of daylight or light. It may describe flowers which open, or stems that move in response to daylight.

divaricate

Spreading far apart.

divergent

Meaning "spreading".

divided

Separated to the base.

division

A method of vegetative propagation by which a clump is divided into several parts, each part (or division) having roots and shoots. Division is usually best carried out when the plant is in a semi-dormant state and when it can be easily dug up. Also a "division" is a classification of plants between kingdom and class. The term "division" may also be used in other contexts such as the division of cells during mitosis or meiosis.

DNA or Deoxyribonucleic acid

Deoxyribonucleic acid is the double helix molecule structure which make up the genes on the chromosomes, in the cells of an organism. The detailed information on which the inheritance of an organism's characteristics are based, is determined by the molecular sequences of certain chemical compounds (amino acids) which are held in the DNA structure. The detailed information on which the inheritance of an organism's characteristics are based, is determined by the molecular sequences of certain chemical compounds (amino acids) which are held in the DNA structure.

dogs

The bitches in season have strong urine which burn off the grass in a lawn.

dogwood anthracnose

Spots develop on leaves and bracts in late spring time. First appear on the base of the tree.

dollar spot

Disorder where straw coloured patches 2.5-5cm across appear on lawn in late summer, enlarge and join together; caused often by iron deficiency.

dolomitic limestone

This is a rock containing calcium carbonate and magnesium carbonate, and when ground may be used to reduce soil acidity.

dominant

Refers to a characteristic, determined genetically, which dominates over other characteristics (recessive). An example might be flower colour where the actual flower colour of the offspring might be red, although the genes might be those for white and red; in this case "red is dominant" and "white is recessive".

dormant

Used to describe the period when a plant makes no growth, usually in the winter, sometimes referred to as a plant's resting period.

dorsal

Referring to lateral organs, the dorsal is the side away from the ground or substratum on which the plant is growing. This may be the same as abaxial.

dorsiventral

Having distinct upper and lower sides.

dot plant

Sometimes used to describe a tall plant used as a point of interest in a floral display.

double flower form

A flower with many petals in several rows and few (if any) stamens.

double or trench digging

A method of digging to two spade depths where soil is heaped up in two stages, whereas single digging means cultivation to one spade depth.

doubly serrate

Large teeth and small teeth alternating.

Douglas fir adelgid

White waxy balls appear on undersides of leaves during summer. Heavy infestations may cause yellowing of foliage.

downy

Covered with short, weak, soft hairs.

downy mildew

Fungal disease that can affect Brassicas, lettuce, spinach, onion, pea and beetroot where the leaves become yellow above, whitish or purple-felted below.

downy mildew of grape

Fungal disease where the first signs are 'oily' spots on leaves, sometimes the disease involves a whole leaf and also fruits, later the spot turns yellow and brown. The fruits become dry, brown and finally become completely mummified.

downy mildew of lettuce

Fungal disease where light-yellow patches appear on lettuce leaves, enlarging to cover whole leaves, with white downy mould on underside.

d-Phenothrin

Insecticide ingredient often used in combination with permethrin or other compounds.

drainage

Describes the flow of water through the soil or growing medium. Drainage can be increased by the addition of coarse material to the soil, or land drains (pipes with small holes in the walls) can be installed below the soil surface to take away excess water. Generally "free-draining" but moisture-retentive soils are desired by most growers (which is perhaps a bit of a contradiction).

drawn

This term may describe plants or seedlings which have become elongated or pale in colour.

drench

Refers to the action of soaking a plant or its roots in water, or in some chemical solution.

dressing

This may refer to a preparation which is applied to the soil, such as a chemical fertilizer which is applied at a particular rate. A top-dressing refers to applications made to the surface of the soil and not dug in.

dribble bar

This can be a tube with small holes which is attached to a watering can, enabling even application.

dried blood

This may be applied to the soil as a high-nitrogen fertilizer which can encourage leaf and shoot growth. It is a by-product of the meat industry.

drilling

Sowing seeds by a mechanical drill on an agricultural scale. On a garden or horticultural scale, straight furrows in the soil may be created by using a stick or a spade, following a garden line or piece of wood. Different seeds require different sowing depths and the seed packet instructions should give guidance.

drip irrigation

This system of watering plants uses pipes with small nozzles that delivers water to individual plants at a slow rate or drip. This allows water to be fed at an optimal rate to the plant and reduces water loss from run-off, evaporation and soaking away. Similar to trickle irrigation in its basic principle.

drip tip

Refers to a pointed leaf tip that helps water run off onto the soil near the roots where it can be taken up by the plant.

drop of lettuce

Disease causing rotting of the rootneck.

dropsy

Another term for oedema.

drought

Lack of water for a long period.

drupe

A fleshy fruit with an inner hard stone (called a pyrene) enclosing the seeds. Examples are plums, cherries, peaches, apricots and nectarines.

dry rot of bulbs and corms

Fungal disease where the whole plants may die back and the corms develop many small sunken lesions, each with numerous tiny black dots which are the fungal fruiting bodies.

dry rot of potatoes

Fungal disease affecting potatoes where tubers in store wrinkle at one end and white or pink fungus visible. The affected tuber tissue becomes black, grey or brown. More likely to be found on stored tubers.

dry spot of capsicum

A disorder affecting Capsicums where yellow spots appear on fruit and later the spots are darker with distinct margins. The fruit are secondarily attacked by micro-organisms.

dry stone wall

A method of building walls without the use of cement. Flattish stones are carefully placed on each other to interlock with each other. Such walls are often used to border fields which have large numbers of stones in the soil, since these can be removed to construct the walls. (The Cotswold region of England has many dry stone walls.)

dulcis

Means "sweet" in Latin.

dumosus

Means "compact - bushy" in Latin.

dung

Refers to manure from animals. Before this is cultivated into the soil it should be allowed to rot down for a period, otherwise it can cause damage to the roots of plants.

duramen

Another name for the heartwood at the centre of a tree trunk.

durus

Means "hard" in Latin.

Dutch elm disease

This is a fungal disease that infects the woody tissue of susceptible elm trees, usually resulting in the death of the tree. The initial infection is often via a beetle vector which burrows under the bark. Nearby trees can be infected via root contact with the diseased tree.

Dutch light

This is a type of glasshouse with sloping sides intended to maximise the amount of light entering the glass.

dwarf

Refers to a small form of a plant, which is more compact than its usual form.

Production v5.9.2 (00577d2)