hard water n - water that contains high concentrations of salts and minerals
harvest n - the yield from plants in a single growing season; v - to gather crops or yields.
hermaphrodite n - A species that displays both male and female flowers on the same plant.
H.I.D- acronym for High Intensity Discharge; describes a family of light fixtures, including mercury vapor, high pressure sodium, and metal halide lamps, that produce light by arcing electricity through various gases
high pressure sodium n - lighting fixture that produces light by passing electricity through vaporized sodium and mercury within an arc tube
hood n - a device used with an HID lighting fixture which directs the light down on the plants
hormone n - a substance, usually a peptide or steroid, produced by the plant to effect physiological activity, such as growth or metabolism
humid adj - containing or characterized by a great deal of water vapor
humidifier n - A device for increasing the humidity in a room, greenhouse, or other enclosure
humidity n - wetness in the atmosphere
humidity dome or tent - clear plastic or glass enclosure placed over a plant or garden to hold in water vapor and increase humidity
hybrid n - an offspring of genetically dissimilar parents or stock; adj - produced by crossbreeding
hybridize v- to breed plants using parents of different varieties; to crossbreed
hybrid vigor n - Increased vigor or other superior qualities arising from the crossbreeding of genetically different plants
hydroponics n - cultivation of plants in nutrient solution rather than in soil; aquiculture
hygrometer n -any of a number of devices used to measure the relative humidity of the atmosphere | 
