Glossary of gardening terms - H:

Harden off
To expose a plant over a week or more to the natural climate after it has been planted grown in greenhouse conditions, so it does not become shocked when planted out.

Hardy
A plant's resistance or tolerance to frosts and freezing temperatures.

Heading back
A pruning tenn for cutting a branch back to the bud or side branch to change the directiol of the growth or enhance bushiness.

Heeling in
A temporary storage of certain plants by burying the roots in soil or sawdust.

Herbaceous
A plant with soft, non-woody tissue.

Honeydew
A sticky, sweet substance produced by aphids and other related insects.

Humus
Vegetable matter which is in the final stages of decomposition.

Hybrid
The offspring of two plants of different species or varieties of plants. Hybrids are created when the pollen from one kind of plant is used to pollinate and entirely different variety, resulting in a new plant altogether.