UCCE Master Gardeners of San Joaquin County
University of California
UCCE Master Gardeners of San Joaquin County

Garden Glossary


A

Abscission
The dropping off of a leaf, fruit, or flower.
Acid
See pH.
Adventitious
Plant structures or organs, such as buds, shoots, or roots, produced in an abnormal position or that arise from other plant tissues.
Aeration (soil)
The process in which air in the spaces around soil particles is renewed.
Aerobic
Occurring only in the presence of oxygen, or requiring oxygen.
Aggregates (soil)
Clusters of soil particles variable in shape, size, and degree of association, such as granules, clods, or prisms, that give a soil its structure.
Agronomy
The science of the production of crops grown on large acreages, such as grains and forages.
Air layering
A propagation technique in which plant parts are rooted while they remain attached to the parent plant.
Alkaline
See pH.
Alternate bearing
The bearing of heavier and then lighter crops of fruits in successive years.
Alternate bud and leaves
The arrangement of buds or leaves singly at a node, usually on either side of the stem.
Anaerobic
Occurring in the absence of oxygen or not requiring oxygen.
Angiosperms
Flowering plants that produce their seeds within a fruit (ovary); the most advanced class of plants.
Anion
A negatively charged ion. See ion.
Annual
A plant in which the entire life cycle is normally completed in a single growing season.
Anther
The upper portion of the stamen that produces pollen grains.
Apical
Located at or pertaining to the apex or tip.
Apical dominance
The influence of a terminal bud (apical bud) in suppressing the growth of lateral buds.
Apical meristem
The tissues at the tip of roots and shoots where cells divide, giving rise to new growth.
Apomictic seed
A seed developed from an unfertilized egg.
Arbor
A shelter of vines or branches or of latticework covered with climbing shrubs or vines.
Arm (grape)
The permanent divisions of the vine arising from the trunk in the case of cordon pruned vines. Arms generaly bear the spurs and canes retained for fruit production.
Arthropods
Invertebrate organisms of the animal kingdom that include insects, spiders, and Crustacea; organisms characterized by an external skeleton and legs with movable segments or joints.
Asexual (or vegetative) propagation
Production of a new plant by using a part of a parent plant, as opposed to sexual union; reproduction of a plant by any means other than seed.
Assimilation
The conversion of food into cell walls and cell contents.
Auxin
A generic term for a group of plant hormones that are active at low concentrations and that regulate plant growth and development, particularly cell division, cell elongation, adventitious root initiation, and bud dormancy.
Available moisture
The amount of water in a soil that roots can absorb.
Axil
The angle formed between a leaf and the stem on which it is attached.

B

Bacteria
Microscopic, one-celled organisms that lack chlorophyll and may be parasites on plants or animals, causing disease; most are beneficial agents of fermentation and decay of organic matter.
Banding
The placement of fertilizer in the soil close to a row of seed.
Bare-root (grape)
A dormant vine that was dug from the wholesale nursery in early winter; it has no soil around its roots and is ready for transplanting.
Bare-root transplanting
A method of transplanting in which plants are dug from the ground with little or no soil left on the roots. Bare-root plants are offered for sale with the soil removed from around the roots. These dormant plants are dug from growing fields, trimmed and freed of soil, and then protected against drying out until planting.
Bark
The outermost tissue of a woody stem that usually includes portions of the phloem.
Bark grafting
A technique in which the scion is inserted between the bark and the xylem of the stock.
Basal
Pertaining to the base or lower part of an organ or plant part.
Basal plate
The short, flattened stem at the base of a bulb.
Beneficials
These are the much favored insects, arachnids, nematodes, and other organisms that eat or parisitize harmful insects and mites. Many beneficials already exist in our gardens, others can be purchased from nurseries or mail-order houses.
Berry (grape)
An individual fruit on a grape cluster.
Biennial
A plant that normally requires two growing seasons to complete its life cycle. Only vegetative growth occurs the first year; flowering and fruiting occur the second year.
Bilateral cordon (grape)
A system of vine training that divides the trunk into two permanent branches, each extending in oposite directions down the vine row and horizontally supported on a trellis wire; commonly referred to as cordon training. The vines are spur prunned.
Binomial system of nomenclature
The system in which the scientific name for any plant or other organism is composed of two Latin terms that designate genus and specific epithet; together, the genus and specific epithet create a species name.
Biological pest control (biocontrol)
The action of parasites, predators, pathogens, or competitors in reducing another organism's population density.
Biotic
Pertaining to life or living.
Bipinnate
Twice pinnate, as in a leaf blade.
Blade
The usually broad, flattened part of a leaf.
Blanching
To whiten (etiolate) a vegetable as it is growing by wrapping the stalk and leaves with paper or outer leaves, or by mounding soil around the portion to be whitened, such as celery.
Blight
A disease causing sudden, severe leaf damage and/or general killing of stems or flowers.
Blossom-end rot
A disorder of tomato fruit in which a sunken dry rot develops on the bottom; associated with calcium deficiency and water stress.
Bolting
Premature flower and seedstalk formation, usually in biennial crops during their first year of growth.
Botany
The scientific study of all facets of plant structure and behavior.
Bract
A modified leaflike structure closely associated with a flower, sometimes petal-like.
Bramble
Any plant of the genus Rubus, such as the blackberry and raspberry.
Branch collar; callus roll
The distinct enlarged portion of woody tissue formed at the base of a branch where it attaches to the trunk. Grape - This is the swollen ridge of bark surrounding a tree branch where it meets the trunk or a bigger branch. When trees are pruned, the branch collar of the limb to be removed should be preserved.
Broadleaf
Plants possessing leaves that are thin, wide, and flattened.
BT (Bacillus Thuringienis)
A bacterial disease that kills caterpillars after being sprayed or dusted on plants. Preparations containing BT can be found under several trade names such as Attack, Dipel, and Thuricide.
Bud
A protuberance on a plant stem, branch, or trunk containing an embryonic leafy or flowering shoot, or both. Grape - Cutting above one of those buds stimulates growth.
Budding
Grafting by inserting a single bud (scion) under the bark of the rootstock.
Bud union; graft union
A swollen area just above the soil level where one variety has been grafted onto the rootstock of another variety. The bud union is not always swollen, and on some older plants it can be difficult to find. On young bare-root trees the bud union may look like a slight bend.
Bulb
An underground storage structure composed of a short stem and overlapping, fleshy leaf bases surrounding a bud, as in onions and tulips.
Bulk density (soil)
The weight per unit of volume of nondisturbed soil that has been completely dried, commonly expressed as grams per cubic centimeter (g/cc); a means of characterizing the amount of macropores and compaction in soil.

C

Calcareous (soil)
A soil containing relatively high amounts of calcium carbonate, usually alkaline.
Callus
Nonspecific tissue that forms a protective covering over a wounded plant surface.
Calyx
The outer or lowest of the series of floral parts composed of the sepals. Usually green and leaflike, but may be colored like the petals.
Cambium
A thin formative layer between the xylem and phloem of most vascular plants that gives rise to new cells and is responsible for secondary growth.
Cane
The woody stem of small fruits such as grape or raspberry; sometimes applied to the stems of roses.
Cane pruning
A system of pruning grapes in which all canes that previously fruited are removed, then a few 1-year-old canes are headed back and usually placed on a trellis.
Canker
A localized area of diseased tissue on a stem, often sunken or swollen, surrounded by healthy tissue.
Canopy (grape)
The leaf-bearing portion of the vine.
Capillary forces
The absorptive force between a liquid (water) and the surrounding material (soil particles), coupled with the cohesive force in the liquid's surface (surface tension); forces that enable water to rise or be held in small spaces against the force of gravity.
Capillary moisture
The water that is held by the soil against the force of gravity and that is available for plant absorption; the amount of water a soil will hold between wilting point and field capacity.
Carbohydrate
An organic molecule composed of carbon, hydrogen, and oxygen, such as sugar, starch, or cellulose.
Carbohydrate-nitrogen balance
The relative proportion of accumulated carbohydrates and nitrogen in stems and leaves of plants; important because it influences flower bud initiation and fruit set.
Cation
A positively charged ion.
Cation exchange
The interchange between a cation in solution and another cation on the surface of a colloidal or other surface-active material such as a particle of clay or organic matter in the soil.
Cation exchange capacity
A measure of soil's ability to retain fertility (cationic forms of plant-essential elements); the sum of exchangeable cations absorbed by a soil, expressed in milliequivalents per 100 g of soil equivalent to the milligrams of H+ that will combine with 100 g of dry soil.
Cell
The structural unit composing the bodies of plants and animals; an organized unit of protoplasm, in plants usually surrounded by a cell wall.
Cell membrane
The structure inside the cell wall that appears to have the function of regulating the flow of nutrients and other materials into and out of the cell.
Cell wall
The membranous covering of a cell secreted by the cytoplasm in growing plants; consists largely of cellulose.
Cellulose
A complex carbohydrate; the chief component of the cell wall in most plants.
Central leader system
A system of tree training in which the trunk is encouraged to form a central axis with branches distributed laterally around it.
Chance seedling
A term commonly used in reference to a cultivar's origin. It is a seedling arising by "chance" (from random, naturally occurring pollination), selected for desirable horticultural traits, and propagated vegetatively to maintain it as a cultivar or clone. "Delicious," the most popular, economically important apple in America, first sprouted as a chance seedling in an Iowa orchard in 1872. "Starking" was the first of several sports produced from "Delicious."
Chelate
A metal ion bonded to an organic molecule from which it can be readily released, such as iron chelate or sequestrene 138 Fe.
Chilling requirement
The number of hours of temperatures required below 45° (7°C), and refers most often to fruit trees that need a certain amount of cold weather in winter in order to bloom and bear fruit well the following year.
Chlorophyll
The green plant pigment that absorbs light energy necessary to the process of photosynthesis.
Chloroplast
A specialized body in the cell cytoplasm that contains chlorophyll.
Chlorosis
Interveinal yellowing of foliage that results from a loss or deficiency of chlorophyll.
Clay
1. Soil particles less than 0.002 mm in diameter. 2. A textural class of soil.
Clonal rootstocks
Clonal rootstocks are vegetatively propagated. Degree of size control and anchorage varies among dwarfing rootstocks. Choices outside of apple for size controlling rootstocks are more limited.
Clone
A clone is a genetically identical group of plants derived and maintained from one individual by vegetative propagation.
Cluster (grape)
The fruiting unit, consisting of the rachis, pedicels, and berries.
Cluster thinning (grape)
Removal of entire clusters after fuit set.
Chlorosis
Interveinal yellowing of foliage that results from a loss or deficiency of chlorophyll.
Cold hardiness (hardy)
The ability of plants to withstand cold injury (autumn-winter).
Cold frame
A bottomless box with a removable clear top used to protect, propagate, or harden plants. No heating device is used.
Cole crop
Any plant of the genus Brassica, of the crucifer family (e.g., cabbage, cauliflower, broccoli).
Coleoptile
Sheathlike pointed structure covering the shoot of grass seedlings; commonly interpreted as the first leaf of the plant above the cotyledon.
Companion planting
A form of intercropping in which specific kinds of plants are reported to mutually benefit from close association in the garden.
Complete flower
Flower having all of the floral parts (stamens, pistil, petals, and sepals).
Complete fertilizer
A fertilizer containing nitrogen, phosphorus, and potassium.
Compound leaf
A leaf divided into two or more parts, or leaflets, all attached to the stem by a single petiole.
Conifers
Plants that bear cone fruits, such as pines, cedars, spruces, and firs.
Contact pesticide
A substance that kills a pest primarily by contacting its tissue rather than by internal absorption.
Cool-season crop
Crop that thrives best or produces highest-quality crops in cool weather.
Cordon (grape)
The main upper woody portion of a grape vine that is trained to a trellis and from which fruiting canes develop; also, a main branch of an espaliered fruit tree.
Core
1. The innermost part of pome and certain other fruits that contains the seed. 2. Receptacle tissue in certain plants, as in the raspberry.
Corm
A short, thickened underground storage organ formed usually by enlargement of the base of the main plant stem.
Corm
The petals of a flower, collectively.
Corm
Unspecified outer tissues of the stem or root.
Cotyledon
A seed leaf that is distinct from the characteristic leaves of a plant.
Cross-pollination
The transfer of pollen from the anther of one plant to the stigma of another plant.
Crown
1. The upper part of a tree or shrub, or the aboveground portion of a plant consisting of branches and leaves. 2. The area where the stem and root join.
Crown
Any plant of the family Cucurbitaceae (e.g., cucumber, squash, watermelon).
Cultivar (cultivated variety)
A cultivar is a contraction of the words "cultivated" and "variety." It is a plant raised or selected in cultivation that retains distinct, uniform characteristics when propagated by appropriate methods. A taxonomic group of plants, originally developed and now maintained under cultivation, that are significant in agriculture (horticulture) and are clearly distinguished by a characteristic that is retained when plants are propagated. In common horticultural usage, cultivar is synonymous with variety. Cultivars can be classified as those which are sexually reproduced and those which are asexually reproduced.
Cuticle
A thin waxy or varnished-like layer that covers the epidermis of aboveground plant parts.
Cutting
A section of a plant that is cut off and rooted to create a new plant, most commonly stem, root, leaf or bud cuttings.
Cytoplasm
The living material in a cell (protoplasm), excluding the nucleus.

D

Damping-off
Rotting of seedlings and cuttings caused by any of several fungi; a fungal attack near the soil line that causes cuttings or emerged seedlings to fall over and die.
Day-neutral plant
A plant in which the flowering period or some other process is not influenced by length of daylight.
Deciduous
Trees or shrubs that drop all their leaves at the end of each growing season; contrasted with evergreen plants.
Determinant
A growth habit in which the main plant stem(s) (axis) terminate(s) in the development of a flower as in corn and some varieties of tomato.
Dicot (dicotyledon)
A flowering plant having two seed leaves, characteristic net-veined leaves, vascular tissues arranged in concentric rings, and flower parts in multiples of fours or fives.
Determinant
The dispersal of molecules from an area of greater concentration to an area of less concentration until the molecules are uniformly distributed.
Determinant
Literally, "two houses"; plants bearing staminate and pistillate flowers (or pollen and seed cones of conifers) on different individuals of the same species; species that produce separate male and female plants.
Division (propagation)
The technique of dividing a plant into two or more parts in which each part is a whole plant; often used with perennials.
Dormancy
A period of inactivity or physiological rest, especially in bulbs, buds, seeds, and spores.
Dormant spray
A solution of horticultural oil and water sprayed in winter on deciduous plants that have gone dormant and dropped their leaves. It kills overwintering pests and some fungi and is sometimes made with lime or sulfur.
Drip line
The imaginary verticle line extended from the outermost branch tips of a tree to the soil directly below. The most active roots are often located along this line.
Drop (grape)
The period when unfertilized or unpollinated flowers fall to the ground prior to fruit set.
Drupe
A simple fleshy fruit in which the inner part of the ovary wall develops into a hard stony or woody endocarp, as in the peach.
Dwarf
A plant that is much smaller when mature than others of its species, often achieved by grafting.
Dwarfing rootstocks
These restrict growth and tree size for reasons such as slower nutrient uptake or smaller root systems. As a rule, these are asexually propagated, but can occur from seed (trifoliate orange).

E

Efficacious
Capable of producing the desired effect; effective.
Element
A substance in its simplest form that cannot be broken down further (e.g., carbon, oxygen, nitrogen).
Embryo
A rudimentary plant formed within a seed.
Endosperm
The tissue in seeds that serves as a food reserve used by the embryo at germination; a large part of a mature seed may be endosperm tissue.
Entomology
The scientific study of insects, including their anatomy, physiology, and behavior.
Epidermis
The outermost layer of cells of the leaf and of young stems and roots.
Espalier system
A method of tree training in which the tree is usually planted against a wall and the main branches trained in a plane parallel to the wall in a geometric design.
Ethylene
A plant hormone that regulates ripening and flowering; ripening fruit and damaged plant tissues give off large quantities; used artificially for many purposes, including ripening and coloring certain fruit.
Etiolate
To cause stems to become elongated, weak, and pale green in color, usually due to insufficient light.
Evapotranspiration (ET)
The loss of water from soil by evaporation from the soil surface and plant transpiration.
Evergreen
Plants that retain leaves or needles longer than one growing season so that some leaves are present throughout the year.
Exocarp
Outermost layer of the fruit wall; often the skin of the fruit.

F

Fasciation
Flattening and enlargement of a branch as if several stems were fused, often accompanied by curving. Believed to be caused by injury to the cells of the bud or by multiple terminal buds arranged in a single plane.
Fastigiate
A narrow, upright growth habit.
Fertilization (botanical)
The union of two gametes to form a zygote, as when a pollen grain germinates and unites with an ovule to form an embryo.
Fertilizer
A substance added to soil to provide plants with essential nutrient ions.
Fertilizer analysis
A statement, usually on the label of a fertilizer container, of the percentages by weights of nitrogen, phosphoric acid, and potash contained in the material.
Fertilizer formula
The quantity and grade of crude stock materials used in making a fertilizer mixture.
Fibrous rooted
A root system in which the roots branch near the crown and become finely divided.
Field capacity
The amount of water a soil can hold against gravity. See capillary moisture.
Filament
The stalk of the stamen supporting the anther.
Fireblight
A bacterial disease that causes the branches and fruit on apple trees, evergreen pear, pyracantha, and members of the rose family to turn black and die. An apt name, the plant looks as if it has been scorched.
Flocculate
To aggregate individual particles into small clusters; the aggregation of soil particles into variously shaped small groups (crumbs, plates, clods, prisms) that create structure.
Floret
An individual flower that is a part of a flower head.
Floricane
In raspberries, the two-year old stems (canes) that produce flowers and fruit.
Flower
The reproductive structure of the angiosperms.
Foot-candle
The density of light striking the inner surface of a sphere with all the surface area being 1 foot away from a 1-candle- power source.
Frass
The solid fecal material produced by insect larvae.
Frost damage
Low temperature injury during some stage of the growing season. Parts affected are flower buds, flowers, and young fruit (spring) or near mature fruit or other tissues (fall).
Fruit
1. (botanical) The matured ovary of a flowering plant containing seed. 2. (horticultural) A fleshy, ripened ovary of a plant eaten for its dessert quality.
Fruit set
The inhibition of a fruit to drop after a flower is pollinated.
Full-slip
In harvesting of melons, the point of maturity when there is easy separation of the fruit from the vine.
Fungi
A lower order of plant organisms, excluding bacteria, that have no chlorophyll or vascular system. Their vegetative body consists of threadlike hyphae, and they often develop spore-producing structures. Some cause diseases of horticultural crops; others (mushrooms) are grown as food; most are beneficial saprophytes.
Fungicide
A substance that kills or inhibits fungi.
Furrow
A depression in the ground surface dug along a prescribed line for planting seed, irrigating, controlling surface water, or reducing soil loss.

G

Gamete
A reproductive body capable of fusion with another; the sperm from the pollen grain and the egg from the ovule.
Gametophyte
Typically a haploid, gamete-producing plant derived from a spore, as in ferns; in higher plants, the sperm and egg and the haploid cells from which they develop.
Gene
A unit of inheritance, located on chromosomes, composed of DNA.
Genetic dwarf
Genetic dwarfs are trees in which the internodes of the cultivar (scion) are greatly compressed. They are naturally small (five to eight feet) trees, even when grafted or budded onto standard, non-dwarfing rootstocks. Genetic dwarfs are best exemplified in peaches and nectarines. "Garden Delicious" is a genetic dwarf apple.
Genus
A group of closely related plants that is clearly differentiated from other groups.
Germination
The beginning or resumption of growth of a seed, embryo, or spore, including pollen grain on a stigma; the sprouting of a seed.
Germ plasm (germplasm)
Hereditary materials (chromosomes, genes, and any other self- propagating particles); the total genetic resources available in the entire population of a crop or species.
Gibberellins (gibberellic acid, GA)
A group of plant hormones regulating stem elongation, seed germination, and other growth.
Girdling
Constricting or removing the outer tissues around a stem as deep or deeper than the cambium, which disrupts the flow of carbohydrates through the phloem. Grape: The removal of a complete ring of outer and innner bark from a shoot, cane, or trunk. Also called ringing. This process temporarily interrupts the downward translocation of metabolites.
Grafting
The process of inserting a part of one plant into or onto another in a way that the two will unite and continue growth as a single unit. Fruit and nut trees: A way to propagate a plant by inserting a section of one plant (the scion) into another plant (the stock).
Granule (soil)
Rounded or subangular, relatively small, dense soil aggregate.
Gravitational water
Water that moves through soil under the force of gravity.
Green manure
A crop plowed under when green for its beneficial effect on soil structure and fertility.
Gray water
Water discharged after household use, including water used for clothes washing, dish washing, and bathing, but excluding water from toilets.
Guard cells
pecialized crescent-shaped epidermal cells that surround a stomate and control its aperture.
Gymnosperms
Seed-producing, nonflowering plants having ovules borne on open cones or scales rather than an enclosed ovary, such as the needle evergreens, pine, fir, and cedar.

H

Half-slip
In harvesting of melons, a stage of maturity in which, as the fruit is pulled from the vine, only a portion of the stem separates easily from the base of the fruit.
Haploid
Having the gametic number of chromosomes, or half the number characteristic of somatic (nonreproductive) cells.
Hardening
Treating plants to make them more resistant to adverse environmental conditions, usually by exposing them gradually to increased light, temperature changes, and drought. Fruit & Nuts: The process of achieving cold hardiness. In a broad sense, it's the process that increases plants ability to survive the impact of unfavorable environmental stress. Water, nitrogen, other practices can affect this process.
Hardening-off
See Hardening.
Hardpan
A subsurface layer of compacted or cemented soil.
Hardscape
The portions of a landscape or garden area that are paved.
Hardwood stem cutting
A mature shoot of the last season's growth that is removed from the plant after the leaves have fallen to be used in propagating new plants.
The upper protion of a vine consisting of the top of the trunk and arms. Vine training: A simple system of vine training in which the upright trunk is held by a stake; it terminates in short permanent arms which bear spurs or canes.
Heading back
Pruning the end of a branch or stem by cutting it back to a bud or side branch. Fruits & Nuts: A type of pruning cut by which the end of a branch is removed to stimulate branching farther back on the branch or trunk.
Heartwood
Nonliving, often darker-colored wood toward the center of a tree trunk that is surrounded by sapwood.
Hedgerow
A widened row sometimes used for bramble fruits in which new canes are permitted to grow between the original plants in the row.
Heel in
A means of preventing roots of Bare-root plants from drying out before they can be set out in the garden. Dig a shallow trench, lay the plant on its side so that roots are in the trench, then cover roots with soil, sawdust, or other material, moistened to keep roots damp.
Herbaceous
A plant or portion of a plant that lacks pronounced woody structure or tissue.
Herbicide
A substance that kills plants.
Honeydew
A sticky substance secreted by aphids and several other sucking insects.
Horizon (soil)
A distinctive soil layer that has well-defined characteristics.
Hormone
An organic substance that, in minute quantities, is usually produced in one part of an organism and transported to another, where it affects or regulates growth and development of tissues.
Horticulture
The art and science of cultivating high-value, often highly perishable crops (sometimes called "garden crops"), including fruits, vegetables, flowers, and landscape trees and shrubs.
Hotbed
Small enclosed garden bed, having a transparent covering, in which the soil is heated.
Humus
Organic matter in a highly decayed state, rich in plant nutrient ions, and very retentive of water when added to soil.
Hybrid
Progeny of a cross between two individuals differing in one or more genes (characteristics).
Hypha
h (pl., hyphae). A threadlike structure composed of one or more tubular cells that make(s) up the body of a fungus.
Hypocotyl
Part of the stem of an embryo or seedling below the cotyledons and above the radicle or embryonic root.

I

Imperfect flower
Flower containing either stamens or pistil but not both.
Incomplete flower
Flower lacking one or more of the floral organs (sepals, petals, stamens, or pistil).
Indeterminant
A growth habit in which the main plant stem(s) (axis) remain(s) vegetative and in which flowers form on axillary buds; growth and flowering can continue indefinitely through the plant's life cycle as in cucumber and some tomato varieties.
Infection
The establishment of the pathogen in the host.
Inflorescence
The arrangement of a flower or flowers on an axis; a flower cluster.
Inoculum
A pathogen or its parts (spores, mycelium, etc.) that can incite infection.
Inorganic
1. Not composed of or derived from plant or animal materials. 2. A compound that does not contain carbon.
Insecticide
A substance that kills insects.
Insecticidal soaps
Biodegradble fatty acids (considered to be environmentally safe) that kill soft-bodied pests such as aphids by clogging their pores.
Instar
The period between molts in the larvae of insects.
Integrated pest management (IPM)
A strategy that centers on long-term prevention or suppression of pest problems through a combination of techniques such as resistant varieties, biological control, cultural practices, habitat modification, and the use of pesticides when careful field monitoring indicates they are needed according to treatment thresholds. When insecticides are used, they are targeted at a specific pest rather than a broad spectrum of insects which may also include beneficials.
Intercropping
Growing two or more crops in the same planting area simultaneously, as in planting squash in between rows of corn.
Internode
The portion of the stem between any two nodes.
Ion
An atom or group of atoms that carries a negative (anion) or positive (cation) charge, formed by the breakup (disassociation) of molecules as happens when certain molecules or compounds are dissolved in water.
IPM
See Integrated Pest Management.
Iron chlorosis
A yellowing or loss of green color in leaf tissue, commonly between the veins, due to an insufficient concentration of iron in the plant.

J

June drop
The dropping of immature tree fruits during the early summer; believed to be caused most frequently by embryo abortion or an extremely large crop load.
Juvenility
The early period in a plant's life cycle characterized by vigorous vegetative growth, sometimes distinctive in form from mature growth, and no flower production.

L

Lateral bud
A bud attached to the side of a stem.
Layering
A method of vegetatively propagating woody plants by covering portions of their stems or branches with moist soil or sphagnum moss so that adventitious root will form. The branch is then removed from the parent plant. See air layering.
Leaching
1. Removing salts, ions, or other soluble substances from soil by abundant irrigation combined with drainage. 2. Movement of soluble materials downward with percolating water.
Leaf
A plant organ typically attached to a stem, varying in size and shape but usually flattened or needlelike and green in color that is concerned primarily with the manufacture of carbohydrates by photosynthesis.
Leaflet
A segment of a compound leaf.
Leaf removal (grape)
Removal of leaves around the clusters on the north or east side of the vine for the purpose of improving air circulation around the clusters, thus reducing disease potential. A plant of the family Leguminosae, such as peas and beans; characterized by a fruit pod that op
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