Glossary of gardening terms - T:

Taproot
A carrotlike root that grows deep into the soil searching for water.

Tender
A plant that is sensitive to cold temperatures.

Thinning out
To prune to make a plant or tree less dense. With seedlings, to remove as many of the small plants as is necessary for the remaining plants to grow to maturity.

Tools
A tool is, among other things, a device that provides a mechanical or mental advantage in accomplishing a task. Most tools employ some form of simple machine, or a combination of them. For example, a hammer simply functions as a lever with the fulcrum (pivot point) being the hand of the user. The further out from the pivot point, the more force is transmitted along the lever. A sword combines a lever and a wedge.

Top dress
To spread organic material, compost or fertiliser onto the soil to enrich it.

Topiary
A technique to prune shrubs and trees into formalised shapes that represent animals and geometrical figures.

Tree
A tree can be defined as a large, perennial, woody plant. Though there is no set definition regarding minimum size, the term generally applies to plants at least 6 m (20 ft) high at maturity and, more importantly, having secondary branches supported on a single main stem or trunk (see shrub for comparison). Compared with most other plant forms, trees are long-lived. A few species of trees grow to 100 m tall, and some can live for several millennia.

Tree House
A house built in the branches of a tree.

Trellis
A system of horizontal joists supported on posts, designed to support growing plants.

Truss
A cluster of flowers at the end of a stem, branch or stalk.

Tuber
A fat underground stem from which a plant grows.

Tuberous root
A thickened underground root that stores food and which is actually a modified stem.