HEAD: 1. The top of a plant consisting of a compact mass of leaves, such as a head of lettuce. 2. A short, dense bunch of flowers. 3. To form a head. 4. To cut back the shoots of plants in order to induce lateral growth.
HEARTWOOD: The older, non-living central wood in a tree.
HEATING CABLE: An electric device used to heat soil in a greenhouse or cold frame.
HEATING SYSTEM: A unit consisting of an adjustable temperature controller and a heat mat; used to maintain soil temperature during germination and seedling development or during root growth of cuttings.
HEAT MAT: A low-voltage heater used to warm soil during seed germination, seedling development, and root growth of cuttings.
HEAVING: The pushing of plants out of the soil because of alternate freezing and thawing action.
HEAVY SOIL: Fine-textured, clay soil.
HEDGE: 1. A barrier or fence formed by bushes or small trees growing together; a closely planted row of shrubbery. 2. To enclose or fence with a hedge; to separate by a hedge.
HEDGE BINDING: Something that is used to bind together the bushes composing a hedge.
HEEL: When a cutting it taken with a "heel" of wood, it means a piece of the old branch or shoot is detached from the old branch or shoot along with the cutting.
HEELING IN: Temporarily covering the base of a plant, especially a dormant plant, with soil for a short time.
HELIOPHILOUS: Fond of the sun; attracted by or becoming most active in sunshine.
HELIOPHOBIC: Shade-loving.
HELIOTROPIC: Turning toward the sun, as leaves or flowers.
HELIOTROPISM: The tendency of plant parts, such as foliage, stems, or flowers, to position themselves according to the direction in which the sun hits them.
HELOBIOUS: Living in swamps or marshes.
HENEQUEN: A strong fiber, similar to sisal, which is produced from the leaves of a Central American Agave and used mainly for making twine. Also spelled heniquen.
HERB: 1. A plant grown for its medicinal or flavoring properties or for its scented foliage. 2. Also refers to plants without persistent, woody stems. This botanical use of the word "herb" is used to distinguish between trees and shrubs.
HERBACEOUS: A non-woody plant in which the upper parts die back to the rootstock at the end of the growing season. An example is the Peony.
HERBAGE: 1. Leafy vegetation. 2. The herbaceous parts of a plant.
HERBAL: Pertaining to or consisting of herbs.
HERBALISM: The knowledge of herbs.
HERBALIST: 1. Someone who is skilled in the knowledge of plants or makes collections of them. 2. A dealer in medicinal plants; a person who treats diseases with botanical remedies only.
HERBARIUM: A collection of dried plants systematically arranged. The plants are attached to sheets of paper, either by small gummed strips of paper or by gluing one side of the specimen.
HERBORIST: An herbalist.
HERBORIZATION: An excursion for studying or collecting plants.
HERCOGAMOUS: Incapable of self-pollination.
HERCOGAMY: A condition in which structural obstacles within a flower make self-pollination impossible.
HERMAPHRODITE: Bisexual, bearing both male and female organs in the same flower; having fully developed stamens and pistils in the same flower.
HESPERIDIUM: A fruit with a leathery rind (i.e. an orange).
HETERAUXESIS: The irregular growth of a plant due to unequal rates of growth in its parts.
HETERODROMOUS: Having the genetic spiral of the branches different from that of the main stem, affecting the way in which leaves are arranged around a stem.
HETERODROMY: A difference in direction of the genetic spiral in the branch and the main stem.
HETEROGAMOUS: Bearing two kinds of flowers in which the sexual parts are different.
HETEROGAMY: The condition of being heterogamous.
HETEROMEROUS: In reference to flowers, having the parts of adjoining whorls different in number.
HETEROMORPHIC: Having irregular, abnormal, or unusual structure, as the leaves of a young plant.
HETEROMORPHISM: The condition of being heteromorphic.
HETEROPHYLLY: The presence of more than one type of leaf on the same plant, such as floating or aerial leaves and submersed leaves on the same aquatic plant.
HETEROSPOROUS: Having more than one kind of asexually produced spores (applied to ferns).
HETEROSTYLED: Having the styles of the flower of two or more different forms.
HETEROTACTIC: Characterized by heterotaxis.
HETEROTAXIS: Abnormal arrangement of parts or organs as compared to a normal type.
HEXAPETALOID: Of a flower, having six petals. Also hexapetalous.