Acclimatization: The adaptation of a plant to a site or to a change in climate.
Acid soil: Soil with a pH value less than 7.0, also sometimes called "sour" soil. See pH, pH scale.
Adhesive disks: On some climbing vines, a circular, flattened organ at the end of a tendril used by the plant to attach itself to a support. Example: Virginia creeper.
Aeration: The act of supplying oxygen to the soil, in a garden by digging or in a lawn by using a spiked tool to punch holes through the sod and thatch into soil.
Aerial roots: On some vines, above-ground, root-like appendages on the stem, used by the plant to attach itself to a support. Example: English ivy.
Alkaline soil: Soil with a pH value more than 7.0, also sometimes called "sweet" soil. See pH, pH scale.
Amendment: A material that is added to the soil to improve its condition, usually being an organic or mineral substance, such as compost, sand, or limestone.
Annual: A plant that completes its life cycle, from seed to the flowering stage and setting seed again, all within a single season.
Antitranspirant: A waxy material applied to foliage to temporarily prevent water loss.
Aphid: Any of the over 4,000 species of small, soft-bodied, pear-shaped insects with mouth parts especially adapted to piercing and sucking sap from the tender tissues of a plant. Also called plant louse.
Average: soil Generally, a loam soil. See loam.
Bacteria: Microorganisms that live in soil, water, plants, and other organic matter that can cause diseases.
Bactericide: Any pesticide that kills bacteria.
Balanced fertilizer: Any fertilizer that contains balanced amounts of nitrogen, phosphorus, and potassium, the three major plant nutrients. Example: 10-10-10 formulation.
Balled-and-burlapped: Term used to describe a nursery plant with its root ball and some soil wrapped in burlap for protection during transport or shipping.
Bare-root: Term used to describe a dormant nursery plant sold without soil around its roots.
Bedding plant: A flowering or foliage plant used for garden display, sold as a small, young plant, most commonly an annual.
Beneficials: Insects, amphibians, or plants that control harmful insects, increase the productivity or fertility of plants, or attract other beneficials or wildlife.
Biennial: A plant requiring two seasons to complete its life cycle; leaves are formed the first year, flowers and seeds the following season. Example: foxglove.
Biological control: Any living or biologically derived agent that controls garden pests and/or diseases. Examples: ladybird beetles eating aphids or BT controlling cabbage worms. See BT.
Blight: A disease that causes plants to wither and die without rotting.
Borers: Worm-like larvae of beetles or clearwing moths that damage both woody and herbaceous plants by boring into and tunneling beneath the bark of tree and shrub trunks and twigs or within the stems of herbaceous plants, often killing the host plant.
Bract: A modified structure found at the base of a flower or flower cluster, usually leaf-like or scaly in appearance but in some plants, such as the dogwood, extremely colorful and showy.
Branch collar: The thickened ring in the area of a tree where a main branch joins the trunk. Broadcast To scatter seeds or fertilizer evenly over a wide area of soil.
Broad-leaf: Term used to describe a plant having broad, flat leaves as opposed to the needlelike leaves of conifers; usually, but not always, deciduous. Examples: Dandelion, Rhododendron.
BT (Bacillus thuringiensis): Any of approximately 30 different bacterial diseases that infect, sicken, and kill insect pests, with different varieties of the bacteria infecting different and very specific pests. Often used to control caterpillars.
Bulb: A swollen underground stem where food is stored during a plant's dormant period. Example: tulip bulb.
Calcareous: A term used to describe alkaline soils containing limestone.
Caliche: A hard, alkaline soil or soil crust containing white calcium carbonate, commonly found in arid western regions.
Cane: A slender woody stem, such as those of rose, raspberry and blackberry bushes.
Canker: A lesion of usually sunken, decayed tissue found most often on plant stems or branches.
Canopy: The uppermost crown of leaves in a tree.
Chlorosis: An unseasonable yellowing of leaves generally caused by disease, nutrient deficiency, or a soil pH imbalance.
Clay soil: Soil composed of very small particles that make it sticky, heavy, and hard to dig Often compacted and slow-draining. Heavy soil.
Cold frame: A bottomless box with a hinged, clear or translucent, plastic or glass top used to harden off and protect plants from the cold.
Compaction: Soil that has become so dense that air and water cannot penetrate, usually caused by foot or vehicular traffic.
Complete fertilizer: Any fertilizer containing nitrogen, phosphorus, and potassium.
Compost: Organic matter, usually vegetative, that has decomposed; used as a soil conditioner, mulch, and disease inhibitor.
Conifer: A cone-bearing tree or shrub; usually refers to evergreen plants.
Contact pesticide: A pesticide that kills insects or other pests on contact.
Controlled-release (slow-release) fertilizer: A fertilizer in which the fertilizer particles are coated with a material that dissolves slowly, thus providing fertilizer to a plant over a long period of time.
Conn: An underground bulblike stem that bears roots and nourishes a plant. Example: gladiolus.
Crown: (1) The basal part of herbaceous perennials from which both the stems and roots grow. (2) The uppermost branches of a tree.
Cultivar (abbr.: cv.): A named plant variety selected from the wild or a garden and cultivated by controlled propagation to preserve certain characteristics. Distinguished in a plant's name by the use of single quotation marks. Example: Thuja occidentalis'Gold King'.
Cutting: A leaf, shoot, root, or bud cut from a parent plant for use in propagation.
Damping off: A fungal disease linked to poor air circulation, which usually attacks seedlings, causing them to collapse and die.
Deadhead: The removal of faded flowers to prevent seeding and to encourage more vigorous blooming.
Deciduous: Trees and shrubs that shed their leaves at the end of the growing season and grow new foliage at the start of the next season.
Diatomaceous earth: Abrasive powder made of the ground, fossilized shells of aquatic diatoms that damages soft-bodied pests, such as snails and slugs, when they crawl over it.
Dieback: The death of stems beginning at the tip, caused by disease, damage, or stress.
Direct seeding, direct sowing: To sow seeds directly on the soil outdoors where they will sprout.
Division: The process of propagating a plant by separating its roots, crown, bulbs, or rhizomes.
Dormancy: A period when a plant temporarily stops growing, usually in winter or in dry weather.
Dormant oil: A refined petroleum product sprayed on dormant plants as a pesticide to smother insects.
Drench: Application of a pesticide to the soil around the roots of a plant.
Drip line: An imaginary line around the outer circumference of a tree's canopy, used as a guide in applying fertilizer, mulch, or for planting.
Espalier: (1) A tree or shrub pruned and trained to grow flat against a wall, trellis, or fence. (2) The training or support of such a plant.
Evergreen: A plant that retains its foliage throughout the year. Example: pine.
Exposure: A description of the variation, intensity, and duration of sunlight, wind, and temperature of a sice.
Eye (1): A growth bud, such as the eye of a potato. (2) The center of a flower, especially when it is of a contrasting color.
Family: Botanically a group of plant genera having overall similar characteristics.
Fertilizer: Any of the numerous organic or synthetic materials containing one or more of the minerals necessary for plant nourishment.
Fl hybrid: A plant bred from two pure-breeding parents to produce a hardier and more productive offspring; will not breed true in the next generation.
Friable: Easily crumbled, as in loam soil. See loam.
Frost hardy: A term used in referring to a plant that is capable of withstanding barely freezing temperatures; usually refers to annuals or tender perennials.
Fungicide: Any substance used to kill or inhibit fungi.
Fungus: A plant organism without chlorophyll that reproduces by spores that can cause diseases.
Gall: An abnormal outgrowth on a plant cause by insects, bacteria, mites, or fungi.
Genus (plural: genera): Botanically, a group of plant species generally similar in flower form, appearance, and growth habit. The first word of a plant's botanical name denotes the genus.
Germinate: To begin to grow; to sprout from seed.
Grafting: A method of plant propagation in which a bud or shoot from one plant is joined to the roots or a shoot of another. See Graft union, Rootstock, Scion.
Graft union: The place on a grafted plant where the bud or shoot and rootstock join. See Grafting.
Greenland: A pulverized rock powder of sandy clay that is used to supply potassium, magnesium, and trace minerals to plants.
Ground-cover: A low-growing plant that spreads quickly to form dense colonies, often used to prevent soil erosion or cover shaded areas. Example: pachysandra.
Habit: The characteristic growth pattern of a plant.
Half-hardy: A term used to describe a plant that can tolerate some cold temperatures or a light frost, but will not overwinter outdoors without protection.
Hardening off: The process of gradually acclimatizing a plant that has been grown indoors to outdoor conditions prior to transplanting. See Acclimatization.
Hardiness: The ability of a plant to survive over a range of hot or cold climactic conditions.
Hardiness zone map: A map created by the United States Department of Agriculture that depicts the average annual minimum temperature range for a specific geographic region.
Hardpan: A hard, dense lower layer of soil formed when minerals leach down and bind with soil particles, blocking drainage and inhibiting root penetration of the soil.
Hardy: Term used to describe a plant that can survive freezing temperatures without protection.
Heat zone map: A map of the United States created by the American Horticultural Society depicting the average number of days per year that exceed 86°F (30°C) for each of the SO states.
Heaving: The pushing of plants out of the soil through the action of alternate freezing and thawing of the soil. Heavy soil A common term sometimes used when referring to clay soil.
Heeling in: To plant in a temporary location. Herbaceous Any plant that has soft or tender upper growth rather than woody growth, specifically, an annual, biennial, or perennial.
Herbicide: A product used to control or kill weeds.
Holdfast: A term most commonly used to refer to the aerial roots or discs of vines by which they attach themselves to supports; also may sometimes be used in referring to tendrils and twining leafstalks.
Honeydew: A viscous liquid excreted by aphids and other sucking insects that acts as a growth medium for certain molds and as a food source for ants. Horticultural oil A refined oil that, when mixed with water, is used as a pesticidal spray; a general term that includes both dormant oil and summer oil.
Humus: Decayed or partially decayed organic matter derived from the natural decomposition of vegetable matter, which is used as a soil amendment, and it may contain plant nutrients.
Hybrid: A plant bred from the cross-fertilization of two or more genetically different parents, whether between different plants in a species, between different species of the same genus, or between plants in different genera.
Inorganic fertilizer: A synthetic fertilizer that provides nutrients to encourage plant growth. Inorganic mulch A mulch made from an inorganic substance, such as plastic sheeting or gravel. See Mulch.
Insecticidal soap: An insecticide, either homemade or commercially prepared, made from the salts of fatty acid in soap.
Insecticide: Any substance that kills insects.
Interplant: To plant two or more types of plants with different bloom times or growth habits together.
Landscaping fabric: Any of a wide variety of modern woven or bonded synthetic materials that allow water and air to pass through. Used for frost and pest protection, shading plants, mulch, and erosion control.
Larva (plural: larvae): The immature growth stage of many insects, such as caterpillars or grubs.
Last frost date: Not an absolute date, but an average of the various dates on which the last frost of winter historically has occurred in a specific geographic area.
Leaf spot (1): Name given to any of numerous viral or bacterial diseases, the main symptom of which is discolored spots on plant foliage. (2) A symptom of such a disease on a leaf.
Leggy: Word used to describe a spindly plant with leafless stems, abnormally elongated stems, or with leaves spaced abnormally far apart on the stem.
Lime: One of several compounds containing calcium and derived from limestone; used in powdered form sprinkled on the ground to provide plants with calcium and to make the soil more alkaline.
Loam: A fertile, well-drained soil that has a relatively equal balance of sand, silt, and clay and is also usually rich in humus. Friable, or crumbly, soil.
Mealybug: Small, soft-bodied, oval insects covered with powdery white filaments. Mealybugs attach themselves to the axils, or crotches, of leaves, pierce the stems, and suck sap from the plant, producing honeydew in the process, upon which sooty mold grows.
Medium: The term used for a soil or soilless mix in which plants are grown, potted, or propagated. It is also called growing medium.
Microclimate: A small area where the climate differs from that of the surrounding area.
Micronutrients: Minerals, such as boron, necessary in small amounts for proper plant growth, also called trace, or minor, elements.
Milky spore disease: A bacterial disease deadly to Japanese beetle grubs, which is used as a pesticide against them. Also sometimes called milky disease.
Miticide: A pesticide, or acaracide, that kills mites.
Mother plant (parent plant): Any plant from which divisions and/or cuttings are taken for plant propagation, or the seed parent in a hybrid cross.
Mulch: A protective organic or inorganic material applied to the soil's surface to provide weed or pest control, conserve moisture, or keep soil cooler in summer and warmer in winter.
Neem: (1) A tall, usually evergreen tree, the neem tree (Aiadirachta indica). which is native to East India. (2) An organic botanical, low toxicity commercial insect repellent and insecticide with long-lasting effects, which is extracted from the seeds of the neem tree.
Nematode: A microscopic worm that lives in soil, plants, or water, with some being beneficial to plants and others being harmful.
Neutral soil: Soil with a pH value of 7.0. See pH and pH scale.
Nitrogen: A major nutrient essential for plant growth. NPK Chemical symbols for nitrogen, phosphorous, and potassium, the three major nutrients in fertilizer.
Nutrient: Any element necessary for plant growth.
Organic fertilizer: Any substance of plant, animal, or mineral origin, such as compost, manure, or green-sand, containing plant nutrients, used as a fertilizer.
Organic matter: Any substance derived from decomposed plant or animal material.
Organic mulch: A mulch made from an organic plant material, such as shredded bark. See Mulch.
Overseeding: A lawn renovation technique in which a lawn or an area of a lawn is reseeded after mowing, raking, and dethatching.
Overwinter: (1) To live through the winter, usually in a dormant state. (2) To shelter marginally hardy plants outdoors or indoors during the winter.
Peat moss: Partially decayed sphagnum moss used in potting media, soil amendments, and as a mulch.
Perennial: (1) A flower that dies down to dormant roots over the winter and resumes new growth in spring. (2) A nonwoody plant that lives several seasons.
Perlite: Granular volcanic rock used to improve aeration in a growing medium.
Pesticide: A substance used to control and destroy insects, fungi, bacterial, mites, weeds, and other pests.
Phosphorus: A major nutrient essential for plant growth. Sometimes also referred to phosphate.
pH: The degree of acidity or alkalinity in the soil, measured numerically; pH that is too high or too low can impede the absorption of soluble nutrients from the soil by plant roots.
pH scale: A scale graded from 0 (pure acid) to 14 (pure lye) used to measure acidity or alkalinity. From the neutral point (7.0) the numbers increase or decrease geometrically; thus pH 5 is 10 times more acid than pH 6; pH 4 is 100 times more acid.
Pinch: To remove a stem's soft growing tip to promote production of side shoots or flowers. Also called pinching out and pinching back.
Plantlet: A new plant, complete with leaves and, usually, roots, arising from the roots, runners, rhizomes, or stems of another plant. Also, a new small plant created by division.
Post-emergent herbicide: An herbicide used to control or destroy established plants.
Potassium: A major nutrient essential to plant growth. Sometimes also referred to as potash. Potting soil Any soil mixture or soilless medium created specifically for growing plants in containers.
Powdery mildew: (1) Any of several fungi which produce a white powdery coating on a plant's surface, particularly leaves. (2) A plant disease caused by said fungi.
Pre-emergent herbicide: An herbicide that acts to control plants before or during germination.
Propagate: To grow new plants from parent stock.
Prune: To cut back the growth of a plant to maintain its vigor, retain its shape, or encourage new growth.
Resistant: Term applied to a plant that is not likely to be affected by a specific stressor, such as disease, insects, pests, or drought.
Rhizome: A swollen underground plant stem that stores food and produces shoots and roots.
Root ball: The roots and accompanying soil visible when a plant is taken from its site and transported.
Rooting hormone, rooting powder: A substance used in propagation to encourage rooting
Rootknot nematode: A minute worm that inhabits the soil and causes extensive damage to the roots of plants.
Rootstock: The section of a plant onto which the shoot or bud of another plant is grafted.
Rosette (basal rosette): A cluster of leaves radiating from one stem in a compact circular arrangement at or near the surface of the soil. Example: dandelion.
Rots: Diseases, characterized by decaying plant tissue, particularly root systems, caused by fungi or bacteria.
Row cover: A light-weight woven or non woven, spun-bonded fabric placed over plants as protection from sunburn, frost or pests.
Runner: A trailing, slender stem that grows along the ground and roots to produce a new plant.
Rust: Any of several fungal diseases that cause disfiguring rusty-looking spots on stems or leaves, especially during cool, damp, late-summer weather.
Sandy soil: A fast-draining granular soil made up of very large particles.
Sawfly larvae: Caterpillar-like larvae that feed in masses on tree foliage, sometimes stripping entire branches or even trees before dropping to the ground to pupate.
Scab: Any of several fungal diseases that create rough raised spots on a plant's leaves or fruit.
Scale: Soft-bodied, sap-sucking insects that, as adults, attach themselves to the plant and form hard, waxy protective shields.
Scarify: To nick, scratch, or apply a chemical treatment to a tough seed coat to induce speedier germination.
Scion: A shoot or bud taken from one plant and grafted onto the rootstock of another. See Grafting.
Scorch: Browning of the leaves along the veins or edges due to hot weather, too much or too little fertilizer, or damage from pesticides.
Self-sow: The spontaneous, unassisted shedding of fertile seeds that will germinate and produce seedlings around or near the parent plant.
Semi-evergreen: A plant whose leaves remain green for part, but not all, of the winter or on which some, but not all, of the foliage is retained in a green condition through the winter. Example: akebia
Sharp sand: Course sand with sharp-edged grains, generally used as a soil amendment.
Shrub: A woody plant with a number of branching stems, often coming from or near the plant's base, and having little or no main trunk.
Side-dress: To spread or sprinkle fertilizer, compost, manure, or other nutrient-rich materials on the soil around the base of a plant or alongside a row.
Silty soil: A soil with a powdery feel, less sticky than clay when wet and tending to be powdery when dry.
Soilless mix: A potting medium that contains no soil; it is usually a combination of peat moss, periite, or vermiculite, and sometimes fertilizer.
Sooty mold: A harmless but unattractive blackish fungus found on the leaves of plants infested with sap-sucking, honeydew-producing insects, such as aphids, scales, and whiteflies.
Species (abbr.: spp.): Botanically, a group of plants sharing at least one distinct trait that sets them apart from all others; a unit of classification that ranks immediately below the genus; the second word in the Latin name of a plant. See Genus.
Spider mite: Any of numerous species of tiny, spiderlike pests that feed on and can seriously damage plant leaves, eventually weakening the host plant. Also sometimes called red mites or mites.
Spores: The dustlike reproductive cells of flowerless plants like ferns, fungi, and mosses.
Stolon: A spreading stem that grows along or under the ground and roots at the tip to produce a new plant.
Stratify: To store seeds in a cool, dark, moist place for a certain period of time to promote germination.
Stress: Any environmental or other factor, such as drought, insects, or diseases, that weakens a plant.
Succulents: Plants that store water in their fleshy leaves or stems. Example: cacti.
Sucker: An undesirable shoot arising from the roots, underground stems, or the rootstock of a grafted plant.
Sulfur (1) A dust or wettable powder used both as a fungicide and, when mixed with other substances, as a miticide and insecticide. (2) In granular form, a soil conditioner used to acidify alkaline soil.
Summer oil A refined petroleum product applied to growing plants to control and destroy insects.
Systemic: Term used to describe a treatment that is absorbed by a plant; may be a fertilizer or an insecticide, fungicide, or a bactericide.
Taproot: The main, downward-growing root, usually long and fleshy, that anchors a plant in the soil.
Tender: Term used to refer to a plant that is susceptible to damage from cold.
Tendril: On a vine, a coiling, thread-like growth used to attach it to a support. Example: nasturtium.
Thatch: Undecomposed plant material that accumulates at the base of lawn grass.
Thinning: To remove surplus seedlings, flowers, branches, or fruits so that the remaining ones grow more vigorously.
Thrips: Tiny, slender, barely visible winged insects that feed on the sap from plant tissues, scraping the tissues with their rasping mouth parts to release the sap and causing significant damage, including scarred fruit and leaves, buds that turn brown and never open, and severely deformed flowers.
Tilth: The friability of the top layer of soil. Tolerant A term used to refer to a plant that can endure specific stressors without undue hardship, such as drought, diseases, pests, or cold.
Top dress: To apply fresh soil, compost, or fertilizer to the soil's surface around the base of a plant without working it into the soil.
Topiary: A tree or shrub pruned into an ornamental shape. Sometimes refers to vines growing on a moss-stuffed frame that has an ornamental shape.
Topsoil: The topmost layer of soil, usually refers to nutrient-rich soil, but topsoil can be of poor quality.
Train: To direct a plant to grow into a desired form.
Transplant: To move a plant from one location to another, one pot to another, or from indoor flats to outdoor beds.
Tree: A woody plant with one thickened main stem (trunk) generally topped by a distinct crown, or canopy, of branches and leaves.
Tuber: A short, thickened, usually underground stem or root where food is stored. Example: potato.
Variegated: In referring to plant leaves, those marked by striations or patterns in contrasting colors.
Variety (abbr.: var.): A distinct variation in a species, which is given a name of its own; often used interchangeably with cuia var.
Vermiculite: A moisture-retaining mineral used to lighten soils and potting mixes.
Vine: A plant with branches that either recline and trail along the ground or climb by twining their stems around a support or by attaching tendrils, aerial roots, or leaf stalks to a support.
Virus: A primitive microorganism that infects living cells and can cause incurable plant diseases .
Volunteers: Plants that grow from self-sown seeds.
Whiteflies: Tiny, white, moth-like sucking insects that feed on leaves, weakening and stunting the host plant and often transmitting viral diseases between plants.
Wilts: Any of a number of bacterial or fungal diseases, usually incurable and fatal, that cause leaves to wilt, turn yellow or brown, wither, and die.
Woody: Word used to describe certain types of plants, specifically, trees and shrubs, with hard stems or trunks that do not die back in winter.
Xeriscaping: Landscaping method based on the use of low-volume irrigation and drought-tolerant plants.