Gardening Glossary

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tannin

A substance occurring in the bark and leaves of some plants that helps protect against predators.

taproot

A thick central root attached directly to a plant's crown. Taproots branch little, if at all.

taxonomy

Classification or naming of plants or animals.

temporary branch

(1) A small shoot or branch left on a young tree's trunk for protection and nourishment. (2) A low lateral allowed to remain until a tree is tall enough to have scaffolds at the desired height.

tender

Not tolerant of frost or cold temperatures. In horticulture, tender does not mean weak or susceptible to insect pests or disease.

tendril

A slender projection used for clinging, usually a modified leaf. Easily seen on vines such as grapes and clematis.

terminal

The tip (apex), usually of a branch or shoot.

terminal bud

The bud at the tip of a stem, trunk, or branch. Its development extends the plants growth.

thatch

A tightly intermingled layer of stems, leaves, and roots, living and dead, that forms between the soil surface and green vegetation of grass.

thermoperiod

The change in temperature from day to night.

thermophillic

High temperature, as in microorganisms that break down organic matter in a hot compost pile.

thigmotrophism

A growth response to touch.

thin

(1) To remove an entire shoot or limb where it originates. (2) To selectively remove plants or fruits to allow remaining plants or fruits to develop.

thorn

A hard, sharp-pointed, leafless branch. Hawthorne is an example of a plant that produces thorns. See prickle.

tiller

A shoot that arises from a plant's crown. Generally associated with grass species.

tissue

A group of cells of the same type having a comon purpose.

tissue culture

The process of generating new plants by placing small pieces of plant material onto a sterile medium. Also called embryo culture.

tolerant

A plant that will produce a normal yield even if infested by a disease or insect pest. See immune, resistant.

topiary

A tree or shrub shaped and sheared into an ornamental, unnatural form, usually a geometric shape or the shape of an animal.

totipotency

The ability of any cell to develop into a complete plant.

trace element

See micronutrient.

transpiration

The process of losing water in the form of vapor through stomata.

transpirational pull

The force exerted by transporation from the leaves which draws water up through the plant.

tree

A woody plant that typically grows more than 12 feet tall and has only one main stem or trunk.

tropism

The tendency of a plant to turn in response to an external stimulus, either by attraction or repulsion, as a leaf turns toward the light. See geotropism, phototropism.

trunk

The main stem of a tree. Also called a bole.

truss

A flower cluster, usually growing at the terminal of a stem or branch.

tuber

An underground storage organ made up of stem tissue. Contains buds on the surface, from which shoots may arise. Potatoes are an example.

tuberous root

An underground storage organ made up of root tissue. Sprouts only from the point where it was attached to the parent plant. Dahlias are an example.

turgor

Cellular water pressure; responsible for keeping cells firm.

twig

A young stem (1 year old or less) that is in the dormant winter stage (has no leaves).

twiner

A stem growing in a spiral fashion around a support.