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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.

tabularis

Means "flat" in Latin.

tallest cactus

The tallest cactus is the Saguaro (Cereus giganteus) from Mexico and Arizona which can attain heights of 17 metres (and live up to 150 years old).

tallest or biggest plant

A Coastal Redwood tree (called the National Geographic Society Tree) in California currently has a height of 111 metre (365 feet). Other tall trees are the Douglas Fir tree which reaches heights of about 100 metre (329 feet), Sitka Spruce to about 96 metre (315 feet), Giant Sequoia to about 94 metre (310 feet) and the Western Hemlock to about 80 metre (261 feet).

tamping the soil

Refers to the act of gently but firmly compacting the soil around a new plant.

tapering

Evenly diminishing

tap-root

The main descending root, often swollen with food reserves (as in carrots). Also used to refer to any strong downward growing root.

tardus

Means "slow - late" in Latin.

tar oil wash

This is a treatment which may be used on fruit trees in the winter months, to give some protection against scale insects, caterpillars, algae and overwintering aphid eggs. The wash is a formulation of tar distillates which is sprayed on the branches and trunks; nearby plants and the ground beneath should be covered so that they are not damaged.

tarsonemid mites

Distorted flowers with white or brown flecks on petals of greenhouse and house plants.

tar spot of Acer

Large, raised black blotches develop on leaves.

tauricus

Means "of the Crimea" in Latin.

taxifolius

Means "yew-like" in Latin.

taxon

A term referring to an individual group into which plants or other living organisms are classified such as family, genus and species. Taxons are defined by taxonomists who study taxonomy.

taxonomist

A person who studies the classification of living organisms. The science of taxonomy takes into account phylogenetic classification which considers the evolution of different species.

taxonomy

The study and practise of classification. A taxonomist studies the features of groups of organisms, and classifies them in a system to better describe and understand the relationships between the members, often in terms of their evolutionary development (phylogenetic classification).

tectus

Means "covered - roofed" in Latin.

temperate

The region below the arctic and sub-arctic regions of the world and above the tropical and sub-tropical regions. Generally temperate plants experience a seasonal range of climate conditions.

temperate deciduous

The natural woodland cover of the British Isles, mid-continental Europe, and areas of eastern USA consists largely of deciduous trees and shrubs. These shed their leaves at the end of the growing season or during a dry season to reduce transpiration. Temperate climates, with four distinct seasons a year, tend to support a mixed woodland habitat, with some conifers but mostly broad-leaved and deciduous trees such as oaks and beech. Human activity has deforested much of the natural woodlands; for example it is estimated that a third of ancient woodlands in England have been destroyed since 1945.

temperature

This can be expressed as centigrade or Fahrenheit. Plants will grow most successfully within certain temperature ranges, relating generally to the climate at their places of origin. The climatic zone refers to a numeric grading (1 to 15) of climates based mainly on temperature ranges, which gives an indication of the hardiness required by a plant to grow successfully.

tender

Used to describe any plant susceptible to damage by frost, and will tolerate temperatures down to about 11C or 52F. Climatic zone of 12.

tender annual

Refers to a plant that germinates, grows, flowers and produces seed in one year, but which needs greenhouse protection in a temperate climate.

tendril

A slender, clasping, twining organ, (often sensitive to contact) formed from a modified leaf or part of a leaf; able to coil around objects it touches to support and anchor the plant.

tenerus

Means "soft - delicate" in Latin.

tenuis

Means "slender - thin" in Latin.

tepal

Refers to part of a perianth that cannot be clearly differentiated into sepal or petal, such as those in the magnolia flower.

terete

A name given to a stem of a plant which is cylindrical and smooth.

terminal

Refers to the top-most leaf, bud, branch, flower or shoot of a plant, which is usually the most vigorously growing point. For example the "terminal bud" is the top-most or end-most bud (it may also be called the "apical bud").

ternate

Meaning "in threes" and usually describes an organ that can be sub-divided evenly into 3, such as a clover leaf.

ternatus

Means "whorls of 3" in Latin.

terracing

This is a similar technique to contouring.

terrarium

A name for a glass or transparent plastic enclosed growing environment for selected plants. Water is recycled in this environment since evapotranspiration generates water vapour which condenses on the internal surfaces and fall back onto the soil. The "Wardian case" (constructed by the botanist Nathaniel Ward, 1791-1868) used this principle to enable tender and rare plants to be transported back to Britain aboard ship.

terrestrial

Meaning that an organism lives on land. More specifically it means that a plant grows in soil or compost rather than in water (aquatic), on rocks or on other plants (epiphytic) etc.

terrestris

Means "grows on the ground" in Latin.

tessellated

Chequered or network patterned.

tessellatus

Means "chequered" in Latin.

testa

In angiosperms, the covering of the seed.

testaceus

Means "brownish yellow" in Latin.

tetramethrin

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

tetraploid

Having 4 sets of chromosomes (twice the diploid number).

texanus

Means "of Texas, USA" in Latin.

textilis

Means "used in weaving" in Latin.

thallus

A simple leaf-like structure found in plants such as the liverworts from the Bryophyta division.

thatch

May refer to a layer of dead organic matter on the surface of a lawn or other area.

thibeticus

Means "of Tibet" in Latin.

thicket

Any plant community dominated by shrubs. Also referred to as 'scrub'.

thinning

Can refer to the process of removing excess seedlings or fruits to allow the remainder to develop with less competition.

thiophanate-methyl

This fungicide is used for controlling fungal diseases on garden and greenhouse ornamentals, fruit and vegetables, houseplants and lawns.

Thiram

A fungicide that may be used to combat soil-borne diseases, or it may be mixed in water as a fungicidal drench.

thrips

Refers to a number of insect species which may be yellow to black in colour. They are more active in warm weather and may also be called thunderflies. They suck the sap of stems, leaves and flowers causing brown or silver streaking and spotting. Some control may be by using insecticides.

throat

The opening or orifice of a tubular or funnel-shaped corolla, or calyx. More generally, the throat refers to the narrowest part of a tubular flower.

Thuja blight

Small blackish brown fungal fruiting bodies appear on surfaces of foliage. Small areas of foliage turn yellow and later brown.

thunderflies

Another name for thrips.

thymifolius

Means "thyme-like" in Latin.

tiliaceus

Means "like a lime" in Latin.

tiller

Refers to shoots that develop from an adventitious bud at the base of the stem, characteristic of grasses, including cereals. By this means and the spreading of the root system, grasses tend to spread out over the land. (This is in addition to the spreading by seed of the plants.)

tilth

The surface layer of the soil, which is fine and crumbly.

tinctorum

Means "used in dyes" in Latin.

tinctus

Means "coloured" in Latin.

tines

A name for the "prongs" of a fork or any pronged implement.

tip bearer

Refers to fruit trees that carry the fruit buds at the end of the shoot of the previous season's growth. (Spur bearing fruit trees produces their fruit on spurs such as apples and pears.)

tip burn

A disorder of lettuce where leaf edges are marked with brown.

tip cutting

A portion of a plant that is removed and used for vegetative propagation. Tip cuttings are greenwood cuttings made from the tip of young non-flowering growth.

tissue

Referring to a group of cells making up a particular structure within an organism, such as vascular tissue made up of xylem and phloem cells.

tissue-culture

A laboratory technique (also called micropropagation) of cloning plantlets using nutritive agar or other growing media. The cells of the explant undergo rapid division and differentiation in the nutrient solution or agar, resulting in rudimentary roots, stems and leaves. In this way it is possible to propagate a great many similar plants which may be virus-free, and suitable for large scale cultivation. At present only certain crops (such as bananas) are successfully using this method of vegetative propagation.

toadstool

A name for the fruiting body of some fungi (which may be poisonous). Mushrooms are also fungal fruiting bodies.

tobacco extract

Used as an insecticide, usually as a spray.

tomato blight

Brown patched appear on leaves. Fruits develop a brown discolouration and may shrink, then rot.

tomato blotchy ripening

Patches of hard yellow or green flesh remain unripened.

tomato cyst eelworm

White cysts on tubers causing knots, goutiness and distortion.

tomato fruit splitting

Tomatoes develop normally but start to split.

tomato ghost spot

On unripe fruits pale green or yellow rings of discolouration appear which doesn't affect the fruit edibility.

tomato greenback

An area of the tomato around the stalk doesn't ripen properly.

tomato leaf mould

Yellow blotches develop on upper leaf surface, beneath a fungal growth.

tomato leaf spot

Disease affecting tomatoes where irregular grey spots with darker margin appear on leaves.

tomato mosaic

Disease affecting tomatoes where irregular light green spots appear on leaves.

tomato moth

Foliage and fruits are eaten by caterpillars

tomato pith necrosis

Upper leaves wilt and turn yellow. Dark brown patches develop on stems.

tomato viruses

Different viruses affect in different ways; yellow discolouration, stunting of fruits.

tomentose

Having a dense, woolly pubescence.

tomentosus

Means "with thick hair" in Latin.

tomentum

A dense covering of matted hairs.

ton

A measure of weight (t) equivalent to 20 cwt or hundred-weight or 1.016 tonne.

tonne

A measure of weight (te) equivalent to 1000 kilogram or 0.984 ton.

tonsus

Means "smooth - shaven" in Latin.

toothed

Bearing teeth (which are larger than serrations)

top cutting

Refers to a stem cutting made from the top shoot of a plant.

top-dressing

Refers to a dressing or preparation which is applied to the soil surface, and is not dug in but left on the soil surface.

top fruit

Refers to any fruit that comes from a tree rather than a bush or shrub, usually meaning fruit such as apples and oranges.

topiary

Refers to the practise of shaping hedges and trees for ornamentation. Usually evergreen plants such as privet, box or yew are used with the support of a wire "topiary frame".

topping

Refers to the removal of the growing point of a plant in order to try and stop the further growth. Examples are the topping of hedging plants when they have reached a suitable size.

topsoil

Refers to the upper layer of soil which usually is the most fertile and contains the most humus. It is likely to be the most workable and in which most cultivation is done. Only larger plants, trees and shrubs have roots that penetrate down into the sub-soil which is beneath the topsoil. It is important to protect the topsoil from soil erosion since it is a valuable resource that will take hundreds of years to regenerate. Much of the planet's land surface has been denuded of topsoil through human activity, and much natural topsoil is thin and fragile (fragile soil) such as that covering much of Australia.

top-working

Refers to the practise of grafting scions onto the stump of an older main stem which is treated as the rootstock. For example, this might be used to rejuvenate fruit trees.

torridus

Means "tropical or parched" in Latin.

tortuosus

Means "twisted - tortuous" in Latin.

torvus

Means "sharp - fierce" in Latin.

total weedkiller

Refers to a herbicide that kills all plants, and might be used for clearing areas of land. However, great care should be used and the instructions followed diligently.

toxic

Meaning poisonous to living organisms.

toxicarius

Means "poisonous" in Latin.

toxin

A toxic or poisonous substance.

trace elements

This may refer to trace nutrients or trace mineral nutrients or micronutrients which are needed by plants in small quantities. It may also refer to any elements found in the soil or elsewhere and could include heavy metals such as mercury, lead etc which are not needed by the plants and may even be at toxic levels.

trace nutrients

These are elements or micronutrients which are only needed by plants in trace amounts for healthy growth. Trace nutrients include: iron, manganese, copper, boron, zinc, molybdenum, sodium, chlorine and cobalt.

trailing

Refers to the growth habit of a plant which has prostrate branches that do not produce roots.

training

Refers to the methods used to get a plant to grow in the shape desired, usually by a combination of selective pruning plus the encouragement and support with tying-in of chosen shoots.

translocation

Refers to the movement of water and nutrients around the tissues of a plant. Translocated or systemic pesticides or herbicides are chemicals which are absorbed by the plant and have their affect within the plant.

transpiration

The loss of water vapour from the plant, especially through open stomata. This aids the movement of water through the plant and the uptake of nutrients. The process called evapotranspiration refers to the loss of water through transpiration and the evaporation of other water on the plant surface, and possibly the soil. If transpiration exceeds the uptake of water by the plant then it will wilt.

transplanting

Moving plants from one place to another, to give them more room to develop.

tree

A woody plant with a definite trunk; the main branching being well above ground level. (The total height is usually greater than 5 metres.)

tree banding

A technique of placing a sticky band around the trunk to trap crawling insects and other small animals as they climb the tree to lay eggs or hibernate.

tree guard

Refers to any protective barrier to stop damage to young trees by deer, rabbits etc.

tree surgery

Refers to the various specialist pruning (done with chain saws) and repair work that may be done to trees, possibly needing climbing and lifting equipment.

trefoil

With three lobes or leaflets; as in a clover leaf.

trellis

Refers to any type of criss-crossed structure made of wood, plastic, wire etc that is designed and placed so that plants may climb up through the gaps and generally be used as a support for plants.

trench

Refers generally to a deeply dug strip of land for a number of purposes. A trench may be used for growing celery (or other crops that need blanching) so that the trench can be backfilled as the plants grow to keep the stems in the dark. A trench may be filled with organic manures and then covered and planted up with crops such as runner beans or sweet peas (which are usually staked for support).

trenching

Refers to a style of deep cultivation in which the soil structure is turned over to a depth of possibly up to 1 metre.

triandrus

Means "triple-stamened" in Latin.

Triassic period

A period of time in the Earth's development 210 - 245 million years ago. A fairly impoverished flora and fauna following the extinctions during the Permian period. However, early insects and reptiles appeared. Corals developed in the sea.

tribe

A classification of plants sometimes used between family or subfamily and genus. Examples are Bambuseae and Paniceae which are tribes of grasses.

trichlorophilus

Means "strongly hairy" in Latin.

Trichlorphon

Used in poisoned bait against ants. It is an organophosphorus insecticide that is also available as a spray to control caterpillars, earwigs and some other insects. It is considered non-persistent but must not be used on edible crops for at least two days before harvesting.

trichome

A name for a hair-like outgrowth from the epidermis of a leaf, which may have a secreting gland at the tip.

trickle irrigation

This system of watering plants delivers water to individual plants at a slow rate but via perforated pipes. 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 drip irrigation in basic principle.

Triclopyr: triethylamine salt of

An active ingredient of some selective translocated weed killers, used on plants such as nettles.

tricolor

Means "3 coloured" in Latin.

trifoliolate

A compound leaf with three leaflets.

Triforine

This is an organic systemic fungicide which is used mainly to control powdery mildew on ornamentals.

trilobus

Means "3 lobed" in Latin.

trimestris

Means "lasts for 3 months" in Latin.

trimmer

Sometime called a strimmer, this powered long-handled tool is used for cutting grass and light vegetation. The cutting edge may be a rapidly rotating nylon line or metal blade. Care needs to be taken when removing grass from around trunks since permanent damage can be done to the bark.

tripartite

Refers to organs such as leaves, petals, sepals, bracts etc that have 3 equal parts.

triple cordon

A trained cordon plant restricted in growth to 3 main stems. They may have 3 different varieties which have been grafted onto the same rootstock; the different varieties being compatible for fertilization of the flowers which will then produce fruit.

triploid

Having 3 sets of chromosomes; triploid plants are usually sterile.

tripterous

Refers to an organ with 3 wings.

triquetrus

Means "3 edged or 3 cornered" in Latin.

tristris

Means "sad - dull coloured" in Latin.

tristylous

Refers to flowers where the styles have 3 different lengths.

tropical

Refers to the regions of the world within the tropics, approximately at latitudes 23 degrees north and south of the equator. Generally tropical plants grow in hot and often humid conditions, and will grow in tropical or glasshouse temperatures down to 17C or 63F. Climatic zone of 13 to 15.

tropicus

Means "of the tropics" in Latin.

tropism

Refers to the movement of a plant in response to a stimulus, such as light or gravity.

trowel

A small hand tool with a blunt blade for general cultivation tasks.

true-breeding

Refers to a plant that through self-fertilization will produce seeds which will grow into plants which have to all appearances identical characteristics as the parent plant.

trumpet

Refers to a flower that is "trumpet-shaped".

truncate

Refers to organs that look as if the "ends have been cut off".

truncatus

Means "truncated" in Latin.

trunk

Refers generally to the thick woody stem with bark that supports a tree.

truss

A compact cluster of flowers.

tube

The fused part of the corolla or calyx.

tuber

A swollen part of a stem or root, formed annually and usually underground (as in the potato which is a root tuber). Also used to refer to a perennial underground swollen stem, as in cyclamens. The tuber is an underground storage organ where the food reserves are mainly in the form of starch. The tuber is often a most suitable means of propagation.

tubercle

A small rounded projection or small tuber.

tuberculatus

Means "warted" in Latin.

tuberosus

Means "having tubers" in Latin.

tubular

In the shape of a tube.

tufa

A form of limestone which is very porous, and used often for rock gardens. It is suitable for alpine gardens where the plants prefer an alkaline soil.

tulip fire

Tulip leaf tips are scorched; straw-coloured streaks on leaves and flowers.

Tulip grey bulb rot

Bulbs fail to emerge above ground. A fungal growth develops.

tundra

Tundra is a region usually at high latitudes, which is almost devoid of trees, due to the presence of permafrost where a deep sub-layer of the soil is permanently frozen. Up to a quarter of the world's land surface has permafrost and in many regions, especially in the mountains, the soil can also be too thin to support tree vegetation. The vegetation consists mostly of grasses, sedges, heather, mosses, lichens and possibly some stunted dwarf trees and shrubs. Arctic tundra stretches in a belt across northern Canada and Eurasia. Alpine tundra is used to describe similar conditions at high altitudes such as those that exist in the Andes Mountains of South America.

tunic

A name for the outer, papery protective layer of a corm or bulb.

tunicated

Refers to the "overlapping and wrapped around way" that scales are arranged, such as in the onion bulb.

turbinate

Means "cone-shaped".

turf

Refers the grass growing in a lawn, or cut slabs of grass including the roots and soil which can be used to lay a new lawn.

turf dollar spot

Grass dies off in patches becoming yellow.

turf ophiobolus patch

Bleached patches develop and spread. Fungal growth may be visible.

turf red thread

Patches of reddish or bleached grass with dark pink, horn-like strands of fungus.

turf snow mould

Small patches of dying grass develop and turn brown, dying patches may become covered in a fungal pink growth.

turf thatch fungal mycelium

Bleached, yellow or reddish patches develop on lawn. A dense mat of fungal growth grows around base of grasses.

turgid

The pressure on the internal walls of a cell or tissue keeps the structure firm or "turgid". When the cells lose their turgidity, the plant tends to wilt.

turgidus

Means "swollen - distended" in Latin.

turgor pressure

This is the pressure on the internal walls of a cell or tissue that keeps the structure firm or turgid. When the cells lose their turgidity, the plant tends to wilt.

turion

A bud arising from a rhizome. Also a fleshy water bud found on some water plants.

turnip gall weevils

Adult beetles lay eggs on roots causing round swellings that enclose grubs.

Turnip mosaic virus

Leaves yellow between veins. Plants may grow distorted or stunted.

turpis

Means "ugly" in Latin.

twig

Any of the minor shoots of a plant, usually referring to small woody branches.

twig blight of apple

Disease affecting apple where petals turn brown-black but remaining on the branches. The branches and trees turn brown.

two, four -D

2,4-D is a systemic selective herbicide which can kill many weeds in the lawn without damaging the grass. It is harmful to most plants apart from grass and it is also harmful to fish.

tying-in

Refers to the act of tying a plant to a support for plants.

type

Often used to indicate the "typical plant form", but botanically it originally referred to the actual specimen from which the plant was described, classified and cultivated.

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