Tendril
A stem or leaf which can wind itself around a support.

Terminal
Organs borne at the tip of a stem.

Thatch
A layer of dead or organic matter which collects between the roots and foliage of lawn grasses.

Thin
Reduce the number of seedlings, buds and branches.

Throat
A tube formed by the corolla of some flowers.

Tilth
The crumbly structure of the soils surface.

Tomentose
Densely covered with delicate hairs.

Topsoil
The dark, fertile soil which is uppermost.

Trace elements
Nutrients required by plants in extremely small amounts.

Transpiration
The loss of water due to heat from the surfaces of stems and leaves.

Transplanting
The movement of a plant from one place to another.

Truss
A tightly packed inflorescence or flower head.

Tuber
A swollen underground stem which is used for storage.

Tunic
The dry covering of corms and some bulbs.

Turgid
Plant material containing sufficient water and therefore not under stress.

U

Umbel
A flower head where all stalks come from the same point and are similar in length.

Union
The join between scion and rootstock.

Unisexual
A flower of only one sex.

V

Variegated
Leaves with markings caused by lack of chlorophyll.

Variety
A naturally occurring variation on a species.

Vegetative reproduction
Division, cuttings and other asexual reproduction.

Virus
A minute organism which can cause disease in a plant.

W

Water shoot
A vigorous shoot growing from an adventitious bud.

Weed
A plant growing in the wrong place.

Weedkiller, contact action
A chemical which only kills the green parts of plants.

Weedkiller, hormone
A chemical which affects the growth of plants.

Weedkiller, residual
A weed killer which stays in the soil for several weeks, useful for killing perennial weed roots.

Weedkiller, selective
A chemical which kills some plants, leaving others unharmed.

Weedkiller, translocated (systemic)
A chemical which is absorbed by the plant and carried into the sap killing the whole plant.

Wetting agent
A chemical added to a spray to improve the liquids adherence to the plant.

Whorl
Leaves or petals arranged in a circle.

Wilting
The drooping of a plant due to lack of water and stress.

Wind-rock
When a plants root system becomes loose due to strong winds and insufficient support.