Half Hardy: A plant that cannot withstand the coldest conditions in a particular climatic zone so needs some protection.
Hardening Off: The process of acclimatising plants grown under protection, in the greenhouse for example, to cooler conditions outdoors.
Hardwood Cutting: A cutting taken from mature wood.
Hardy: A plant that can withstand the extremes of climatic conditions in the area it is grown.
Heel: A small piece of bark at the bottom of a cutting when it is removed from the main stem. This often makes rooting the cutting easier.
Heeling In: Putting a plant in a temporary position until it can be permanently planted.
Herb: A plant grown for flavoring food or for medicinal purposes.
Herbaceous: Usually refers to perennials, these are plants with non-woody stems that die back to the roots at the end of the growing season.
Herbicide: A chemical used to kill weeds.
Honeydew: The sticky secretion from aphids, etc.
Humus: The beneficial decayed vegetable matter that helps to form soil.
Hybrid:– The offspring of two different plants.
Hydroponics: Growing plants in nutrient enriched water.
Indehiscent: A fruit that remains closed so doesn’t open to release seeds.
Inflorescence: A group of flowers growing on one stem.
Inorganic: Usually refers to fertilizers – those that do not derive from living material.
Insecticide: A substance, either chemical or organic, used to kills insects.
Internodal Cutting: A cutting taken by cutting between two nodes.
John Innes Compost: A loam based compost.
Knocking Out: Removing a plant from a pot to repot or check root ball.
Layering: A method of propagation used to make a new plant before severing it from the old plant.
Leaching: Losing nutrients from top soil by water draining them out.
Leaf Bud Cutting: A cutting taken from a small piece of stem with one or two leaves or buds.
Leaf Cutting: A cutting taken from a whole or part of a leaf.
Leaf Mold: Decomposed leaves used for compost and to add body to garden soil.
Leaflet: A sub-division of a compound leaf.
Leggy: Weak, tall growth on a plant, sometimes caused by keeping a plant in too warm conditions too long.
Legume: Dehiscent fruit that splits into two when mature.
Lithophyte: A plant that grows naturally on rocky ground.
Loam: Good soil, usually easy to work, with equal proportions of silt, sand, and clay and with a high proportion of humus.