Glossary - H-L
Hardening-off – The process whereby transplants top growth and develop greater tolerance to stress.
Hazard – The combination of a pesticide’s toxicity and your exposure to the pesticide
Heavy soil – A soil that contains a high proportion of clay and is poorly drained.
Heirloom cultivars – Cultivars that are more than 100 years old and whose seeds are passed down from generation to generation.
Hill plantings – Planting multiple seeds together in clumps.
Honeydew – A round melon with smooth rind and green flesh.
Hotbed – A heated cold frame.
Hot caps – Individual structures placed over a vegetable plant that warm the temperature and protect the plant against frost.
Humus – A substance that results from the decay of organic matter by living organisms.
Hyphae – A fine threadlike structure of cell formed by fungi affecting a plant.
Incidental organisms – Organisms that have little or no impact on crop production.
Inhalation exposure – Pesticide is absorbed by breathing-in through the lungs.
Integrated Pest Management – An approach to pest management that uses a variety of techniques to identify and if necessary manage a pest.
Intercropping – Planting more than one crop in an area at the same time.
Interplanting (companion planting) – Growing two or more plants together in a close association.
IR mulches – Mulches that allow infrared radiation to penetrate through the mulch but reflects photosynthetically active radiation.
LD50 – Dose required to kill 50% of laboratory test animals.
Leaching – the downward movement of water and nutrients from the soil surface to the water table due to gravity.
Leafhoppers – Small (less than 1/2 inch long) wedge-shaped slender insects that disperse rapidly when disturbed.
Leggy or spindly – Excessive and weak stem growth due to exposure to adverse environmental conditions.
Legume – Plant that has a symbiotic relationship with rhizobium bacteria.
Light soil – A soil that contains a high proportion of sand.
Ligule – Structures that occur where the leaf blade attaches to the stalk.