Horticulture Terminology

Air drainage The flow of cold air down a hill. Plant crops that are sensitive to late spring and early fall frost on slopes, preferably south-facing, so that cold air will drain downhill and settle in the low spots below the planted area

Air layering A propagation method. A cut is made three-quartets of the way through the stem at an angle of 45 degrees. A toothpick is inserted to keep the cut from sealing itself closed. The cut is wrapped in sphagnum moss that has been soaked in water and wrung out. This is then wrapped in plastic and tied at the top and bottom with ties.

Alternate leaf arrangement Leaves are arranged at one leaf per node on different sides along the stem.

Annuals Plants that complete their life cycles in one year or less.

Anther The part of the flower (on the upper part of the stamen) in which pollen is produced.

Anthracnose A type of leaf or fruit spot disease caused by a fungus.

Arms In a grape plant, all main branches two years and older.

Asexual reproduction Duplicating a plant from any cell, tissue or organ of that plant.

Axillary buds Buds that are borne laterally on the stem in the axils of the leaves.

Biennials Plants that require 2 years, or 2 growing seasons with a dormant period in between, to complete their life cycles.

Biological control Reducing pests by utilizing other organisms. For example, controlling gypsy moths by using Bacillus thuringensis, a disease that affects the gypsy moth and is readily available in garden centers.

Blade The flattened, green portion of the leaf.

Bolting Going to seed. Plants will produce a flower stalk and seeds, and then die before the end of the season. Lettuce and other crops will bolt during very hot temperatures. Unless you are growing your crop for the seeds, you want to delay bolting.

Botrytis blight A gray, felt-type mold that covers parts of a plant and causes stunting, dieback, and distorted growth.

Branch The part of the tree that arises from the trunk and supports shoots, twigs and leaves. Budding. A type of grafting in which a non-fruitful (vegetative) scion is placed in a stock plant.

Buds An undeveloped stem, consisting of a tiny bundle of cells, from which leaves, lateral buds, flower parts or all three will arise.

Bulb A budlike structure that consists of a small stem with closely crowded fleshy or papery leaves or leaf bases.

Bulbil An aerial bulblet.

Bulblet Miniature bulbs that develop from meristems in the axils of scaly bulbs.

Canes Previous season’s growth from the arms or trunk of a grape plant; or, the supporting part of the raspberry plant, similar in function to the trunk of a tree.

Capsule Simple, dry, dehiscent (see definition of dehiscent) fruit with two or more locules (the cavities of the ovary of the pistil of a flower) which split in various ways.

Catkin A type of spike arrangement of flowers on the floral axis that has unisexual flowers made up of sepals and petals.

Certified seed The progeny of registered seed stock. It is the final stage in the expansion program and is certified with a metal seal and blue tag.

Chilling injury Damage to certain horticultural products, such as banana, papaya, cucumber and sweet potato, which results from exposure to cold but above-freezing temperatures.

Chilling requirement A cold period required by certain plants and plant parts to break physiological dormancy or rest. The chilling requirement is expressed in terms of the required number of hours at 7 degrees centigrade or less.

Cold storage A type of insulated storage utilizing mechanical refrigeration to maintain a stable, cold temperature for long-term storage.

Commercial floriculture Area of horticulture that includes the commercial production and distribution of cut flowers, flowering pot plants, foliage plants and bedding plants.

Complete fertilizer A fertilizer that contains nitrogen, phosphorus, and potassium.

Complete flower Flower composed of a short axis or receptacle from which arise four sets of floral parts-sepals, petals, stamens, and pistils.

Compound leaf A leaf with the blade divided into several leaflets or sections.

Compound umbel A type of flower structure in which a series of simple umbels (see definition of umbel) arise from the same point on the main axis.

Corms Short, fleshy, underground stems with few nodes and very short spaces between nodes. Gladiolus and crocus are cormous plants.

Corymb Type of raceme flower cluster in which the pedicels of the lower flowers are longer than the pedicels of the upper flowers, resulting in a flattopped flower cluster.

Cross-pollination The process in which pollen is transferred from an anther (the upper part of the stamen in which pollen is produced) of one flower to the stigma (the pollen-receiving site of the pistil) of a second flower of a different cultivar.

Cultivar A plant derived from a cultivated variety that has originated and persisted under cultivation, not necessarily referable to a botanical species, and of botanical or horticultural importance, requiring a name.

Cuticle The waxy covering on leaves or fruit, which protects the tissue against excess moisture loss.

Cuttings Detached vegetative plant parts which when placed under conditions favorable for regeneration will develop into a complete plant with characteristics identical to the parent plant

Cyme A broad, more-or-less flat-topped determinate (having a fixed number) flower structure in which the central flowers bloom first.

Day-neutral plant A plant that will flower under any daylength.

Deciduous Trees or plants that shed their leaves every year.

Dehiscent Type of dry fruit in which the carpel (a simple pistil) splits along definite seams at maturity. Determinate growth. Limited growth.

Dioecious Species that produce male and female flowers on separate plants.

Disbudding The removal of vegetative or flower buds.

Diseased plant A plant that is abnormal because of a disease-causing organism or virus.

Dormancy A state of suspended growth or the lack of outwardly visible activity caused by environmental or internal factors.

Drip irrigation The application of small quantities of water directly to the root zone through various types of delivery systems on a daily basis.

Drupe Type of fruit with a thin outer skinlike region, a center portion that is thick and fleshy, and an inner area that is hard and stony.

Endocarp The inner area of the fruit wall. Entomology. The study of insects.

Epidermis The outer layer of cells of all parts of a young plant and of some parts of older plants, such as leaves and fruits. These cells are usually covered with a waxy substance, called the cuticle, that minimizes water loss.

Exocarp The outer skinlike region of the fruit wall.

Fallow A system in which land is left without a crop for an extended period to accumulate moisture and restore nutrients.

Fleshy fruits Classification of fruits that includes the berry, drupe, and pome. They have a fruit wall that is soft and fleshy at maturity.

Floriculture The study of growing, marketing, and arranging flowers and foliage plants.

Flower A shoot of determinate (limited in number) growth with modified leaves that is supported by a short stem; the structure involved in the reproductive processes of plants that bear enclosed seeds in their fruits.

Forcing The manipulation of environmental factors which makes it possible to produce a marketable pot plant or cut flower out of season.

Foundation seed Seed stock handled to most nearly maintain specific genetic identity and purity under supervised or approved production methods certified by the agency.

Frost pocket A depression in the ground into which cold air drains but from which it cannot escape, thus causing it to be an area very subject to freeze injury.

Fruit An expanded and ripened ovary with attached and subtending reproductive structures. Genes. Basic units of hereditary material that dictate the characteristics of individuals.

Germination The initiation of active growth by the embryo, resulting in the rupture of seed coverings and the emergence of a new seedling plant capable of independent existence.

Grafting The joining of two separate structures, such as a root and stem or two stems, so that by tissue regeneration they form a union and grow as one plant

Growing season The period from the last spring freeze until the first freeze in the fall. In the United States this ranges from about 100 to 365 days.

Hardening The result of many changes that occur in a plant as it develops resistance to adverse conditions, especially cold.

"Hardening off" The treatment of tender plants to enable them to survive a more adverse environment. Treatments involve withholding nutrients, lowering temperatures, allowing temporary wilting, and other methods to slow growth rate.

Hardpan A layer in the soil that cannot be penetrated and which restricts root penetration as well as movement of air and water.

Hardwood cuttings Cuttings made from woody deciduous species and narrow-leaved evergreen species, such as grape and hemlocks.

Heading back Type of pruning cut where the end portion of the shoot is removed but the portion at the base is not.

Herbaceous cuttings Cuttings made from herbaceous plants (see definition below), such as chrysanthemums, coleus, and geraniums.

Herbaceous perennials Plants with soft, succulent stems whose tops are killed back by frost in many temperate and colder climates, but whose roots and crowns remain alive and send out top growth when favorable growing conditions return.

Herbarium A collection of plant specimens that have been taxonomically classified, pressed, dried, and mounted on a sheet of herbarium paper.

HerbicideA material that will kill plants. Herbicides may kill essentially all plants or be quite selective in their activity.

High-pressure sprayer A sprayer using a high-pressure pump to force the spray through nozzles for both creating a fine spray and delivery to the plant.

Horticulture The intensive cultivation of plants.

Humus A dark-colored organic material that is the product of organic matter breakdown by both microorganisms and chemical reactions.

Hybrid In its simplest form, a first-generation cross between two genetically diverse parents. Imperfect flower. Flower lacking either the stamen or the pistil.

Incomplete flower Flower lacking one or more of the fours sets of floral parts.

Indehiscent Type of dry fruit in which the fruit wall does not split at any certain point or seam at maturity. Indeterminate growth. Growth that is potentially limitless.

Inflorescence The arrangement of the flowers on the floral axis-a flower cluster.

Interstock Intermediate stem piece that is grafted between the upper and lower pars of the graft.

Landscape design The profession concerned with the planning and planting of outdoor space to secure the most desirable relationship between land forms, architecture, and plans to best meet human needs for function and beauty.

layering A vegetative method of propagation that produces new individuals by producing adventitious roots (roots growing from unusual places) before the new plant is separated from the parent plant.

Leaching The downward movement of nutrients or salts through the soil profile in soil water. Leaching accounts for nutrient losses but can also be beneficial in ridding a soil of excess salts.

Leaf arrangement The arrangement of leaves on the stem.

Leaf-bud cuttings Cuttings consisting of a leaf blade, leaf stalk, and a short piece of the stem. Leaf cuttings. Entire leaves with or without the leaf stalks.

Leaflets Individual parts of a compound leaf.

Leaves Vegetative plant parts that are lateral outgrowths of stems that have developed special structures for photosynthesis.

Legume A simple, dry, dehiscent (see definition of dehiscent) fruit with one locale that splits along two seams.

Lime Ground limestone that is used to raise soil pH.

Loam A type of soil consisting of sand, clay, and organic matter. Locales. The cavities of the ovary of the pistil of a flower.

Long-day (short-night) plant A plant that requires a day longer than its critical daylength to flower.

Malling-Merton series A group of apple rootstocks that were the result of the crossing the Malling series with the ‘Northern Spy’ to add resistance to woolly aphids.

Malling series A group of apple rootstocks that originated at the East Malling Research Station in England.

Market gardening The growing of an assortment of vegetables for local or roadside markets. Mesocarp. The center portion of the fruit wall.

Micronutrient An essential nutrient that is needed in small amounts; also called a trace or minor element. Monoecious. Plants that produce male and female flowers on the same plant.

Mound or stool layering A layering procedure in which the new shoots develop in spring and soil is mounded around their bases, excluding light and enhancing root formation.

Mulch A material applied to the surface of a soil for a variety of purposes such as conservation of moisture, stabilization of soil temperature, and suppression of weed growth.

Nursery grower A person who produces or distributes ornamental plants.

Nut An indehiscent dry fruit similar to the achene except that the fruit wall is hard throughout. Offsets. Miniature bulbs grown to full size.

Offshoots Short, horizontal stems that occur in whorls or near whorls at the crown of stems.

Olericulture The study of vegetable production.

Opposite leaves Leaves arising from opposite sides of the same node.

Organic matter Materials rich in carbon of either plant or animal origin, which exist in all stages of decomposition of soils.

Ovary Part of the pistil that contains one or many small bodies known as ovules. Ovule. The immature seed in the ovary.

Palmate leaf A compound leaf with all the leaflets arising from one point at the end of the leaf stalk

Palmately veined leaves Leaves with netted veins having several large veins radiating into the blade from the leaf stalk at the level where the leaf stalk and blade join.

Panicle Type of flower cluster with either a cluster of racemes or corymbs (see definitions), distinctly branched.

Parallel venation Leaves with large veins that are essentially parallel to one another and are not connected by lateral veins.

Peduncle The short stem of the flower cluster.

Pepos Berries that have a hard rind around the fruit.

Perennials Plants that do not die after flowering but live from year to year.

Perfect flower A flower that has both a pistil (or pistils) and stamens but may lack sepals, petals, or both. Perianth. Structure consisting of the sepals and petals.

Pericarp The fruit wall, consisting of three distinct layers; the exocarp, the mesocarp, and the endocarp.

Pest management The control of a pest or group of pests by a broad range of techniques from biological control to pesticides. The goal is to keep damage below economic levels without completely eliminating the pest.

Petals Structures collectively making the corolla, which protect the inner reproductive structures and often attract insects by either their color or their nectar and thus facilitate pollination.

Petiole The leaf stalk.

pH A measure of acidity or alkalinity, expressed as the negative log of the hydrogen ion concentration. A pH of 7 is neutral; less than 7 is acidic more than 7 is basic

Pinching Breaking off the uppermost growing point, thus allowing the willary buds to start to grow. This promotes outward growth rather than upward growth.

Pinnate leaf A compound leaf with the leaflets arranged along both sides of the midrib.

Pinnately veined leaves Leaves with netted veins where secondary veins extend laterally from a single midrib.

Pistil The female reproductive organ, consisting of the stigma, style, and ovary. Plant growth. A permanent increase in volume, dry weight, or both

Plant pathogen A microorganism that causes a plant disease.

Plant propagation Increase in numbers or perpetuation of a species by reproduction.

Pome Type of fruit in which the portions produced by the pericarp are enclosed within fleshy parts that are derived from parts of the flower other than the ovary. An apple is a pome.

Pomology The study of fruit production.

Pot-bound Having restricted root growth and a circular pattern of root growth caused by a too-small container.

Pruning Removal of plant parts such as buds, developed shoots, and roots to maintain a desirable form by controlling the direction and amount of growth.

Raceme Type of flower cluster in which stalked flowers are on pedicels approximately equal in length on a single floral axis.

Rest A state of suspended growth or outwardly visible activity due to internal physiological factors. Also referred to as physiological dormancy.

Rhizome Horizontal stems that grow underground. They serve as storage organs and a means of vegetative reproduction.

Root Vegetative plant part that anchors the plant, absorbs water and minerals in solution, and often stores food.

Root cuttings Cuttings 5 to 15 cm long made from root sections in the fall or winter.

Runner A slender stolon (see definition) with elongated internodes. These root at the nodes that touch the ground. Example: strawberries.

Rust A type of fungal disease that requires two hosts. For example, White Pine Blister Rust alternates between white pine and Ribes sp. Gives a rusty appearance to the plant.

Samara An indehiscent dry fruit with either one or two seeds, in which pericarp bears a flattened wing-like outgrowth. The "helicopters" of the maple trees are double-samaras.

Scales Modified leaves that protect structures.

Scaling A type of propagation that separates bulb scales from the mother bulb to induce the formation of bulblets.

Scarification The chemical or physical treatment given to some seeds to break or weaken the seed coat sufficiently for germination to occur.

Scion (cion) The upper part of the union of a graft.

Seed Plant embryo with associated stored food encased in a protective seed coat.

Self-pollination The process by which pollen is transferred from the pollen producing section of the plant to the pollen receiving part of the plant of the same flower or another flower of the same cultivar.

Semihardwood cuttingsCuttings made from woody, broad-leaved evergreen species such as ligustrum and holly.

Sepals Structures that usually form the outermost whorl of the flower; collectively, the calyx.

Separation The use of bulbs and corms in propagation that utilizes the naturally detachable parts.

Serrate leaf A leaf with serrations or "teeth" along the edge of the leaf.

SessileWithout a petiole (as in some leaves), or without a pedicel (as in some flowers and fruits).

Sexual reproduction The reproduction of plants through a sexual process involving cell division.

Shoot Stem, 1 year old or less, that possesses leaves.

Simple bud Bud containing either leaf or flower primordia, but not both.

Simple layering A method similar to tip layering, except that the stem behind the end of the branch is covered with soil and the tip remains above ground.

Simple leaves Leaf blades consisting of one unit.

Sinus The indentation of a leaf. Sinuses alternate with lobes.

Slow-release fertilizer A fertilizer that is made by coating the particles with a wax or other insoluble or very slowly soluble material to provide a predictable, slow release of the encapsulated materials.

Softwood cuttings Cuttings taken from soft, succulent, new spring growth of deciduous or evergreen species of woody plants.

Soil. The outer, weather layer of the earth’s crust that has the potential to support plant life. Soil is made up of inorganic particles, organic matter, microorganisms, water, and air.

Soil management The practices used in treating a soil, which may include various types of tillage and production systems.

Soil structure The arrangement of individual soil particles.

Spike Flower cluster of an indeterminate (unlimited number) raceme of sessile flowers attached to the floral axis with the oldest flowers at the base.

Spikelet Diminutive type of spike inflorescence found in grasses.

Spines Sharp-pointed woody structures, usually modified from a leaf or part of a leaf.

Stamen Part of the flower consisting of the anther, in which pollen is produced, and a slender filament that holds the anther in a position favorable for pollen dispersal. Male reproductive organ.

Staminate flower Flower in which only the stamens (male reproductive parts) are present; there are no pistils (female reproductive parts).

Stigma The pollen-receiving site of the pistil.

Stipules Leaflike appendages often found on either side of the base of the petiole; they may subtend the leaf, but they are not actual parts of the leaf.

Stock (rootstock) The lower part of a graft.

Stolon An aboveground stem that reclines or becomes prostrate and may form roots at the nodes that may come into contact with the ground.

Stratification The storing of seeds at low temperatures under moist conditions to break physiological dormancy or rest.

Succulent leaves Water storage structures characteristic of plants in and and semiarid regions.

Taproot Primary root that persists and maintains its dominance.

Temperate fruit A fruit plant that requires a cool period and is deciduous. Examples are apple, pear, and peach.

Tendrils Slender, twining leaf modifications used for support, as in the terminal leaflets of the grape.

Terminal buds Large and vigorous buds at the tips of stems, responsible for terminal growth.

Thorn A short, sharp-pointed branch.

Tip layering Layering in which rooting takes place near the tip of the current season’s shoot, which naturally falls to the ground.

Tissue culture The growing of masses of unorganized cells on agar or in liquid suspension. Useful for the rapid asexual multiplication of plants.

Topworking Grafting procedure by which branches of trees are changed to a more desirable cultivar.

Trickle irrigation The application of small quantities of water directly to the root zone through various types of delivery systems on a daily basis.

True leaves The first leaves to emerge after the germination of a seed.

Tubers Enlarged underground stems serving as storage organs of starch or related materials. Potatoes are tubers.

Twig Stem, 1 year old or less, without leaves.

Umbel Type of flower cluster in which the pedicels arise from a common point and are about equal in length.

Variegated Leaves with green and white striped pattern instead of the typical all-green look.

Vegetable The edible portion of an herbaceous garden plant.

Weed A plant growing where it is not wanted.

"Wet feet" A condition where plants are exposed to excess soil moisture caused by flooding or a high water table.

Whorled arrangement Three or more leaves at a node.

Wilt Loss of rigidity and drooping of plant parts caused by many different plant diseases. Generally, it involves an interference with water conduction inside the stems.

Woody perennials Plants with woody fiber.

Yellows A type of disease, common among some flowers, that is caused by a virus or mycoplasma-tike organism. This disease causes stunting and a yellowish appearance.