Glossary of lawn care terms used on this site.

Acid soil: A soil whose reaction is below pH 7.0.

Aerification (soil): The mechanical removal of soil cores to improve soil air exchange, relieve soil compaction and inmprove water and nutrient movement into the soil.

Alkaline soil: A soil whose reaction is above pH 7.0.

Annual plant: A plant whose life cycle lasts only one growing season, from seed to blooms to seed.

Annual: Winter annual: A plant that begins growth in the fall, survives over winter, flowers, produces seed and dies the following season. Summer annual: begins growth in spring, flowers, produces seed and dies when cool temperatures arrive in the Fall.

Beneficial Insect: An insect that attacks lawn/garden pests by eating or laying its eggs in them, thereby controlling their population.

Biennial: A plant whose normal growth cycle spans two growing seasons. Many biennials produce roots and a cluster of leaves near the surface of the ground the first year; flower, produce seed and die the second year.

Biodegradable: Capable of being broken down into simpler compounds by microorganisms. Organic materials are biodegradable.

Biological Pest Control: Using living organisms (beneficial insects, bacteria) to destroy insect pests.

Bio-Solids: The nutrient-rich organic materials left over from the treatment of sewage sludge. Often found in commercial compost and may contain concentrations of heavy metals.

Blade (leaf): The flattened portion of the leaf projecting outward from the main shoot axis and located above the sheath.

Blend (seed): A combination of two or more varieties (cultivars) of a single turfgrass species.

Botanical Insecticide: Derived from plants, these organic pesticides provide a quick "knock down" to a large number of pests. They leave no residues and breakdown quickly in the environment.

Breakdown processes: Refers to the chemical and/or microbial actions in the soil responsible for the decomposition of various organic residues, including most pesticides.

Broadcast application: Uniform distribution of a pesticide or fertilizer over an entire area.

Buffer zone (or strip): Generally considered to be an unmanaged area of vegetation along a shoreline to help slow down and filter runoff before entering the water body and prevent soil erosion.

Broadleaf herbicide: A weed killer designed to specifically kill broadleaf plants.

Broadleaf weeds: A term applied to nongrass-like weeds; often used in the context of weed control. Examples include dandelion, clover, and chickweed.

Bunch-type growth: Plant development through the formation of clusters of tillers (shoots) at or near the soil surface without the production of rhizomes or stolons.

Burn: Fertilizers are salts, much like our familiar table salt except that they contain various plant nutrients. Injury to plant shoots or roots caused by dehydration due to contact with high concentrations of salts.

Calibrating: The process of checking a mechanical applicator, such as a fertilizer spreader, to insure that it will accurately deliver the right amount of material to the right amount of area.

Chlorophyll: The green pigment in leaves. When a plant is healthy it is very prominent.

Chlorosis: Absence of the green pigment chlorophyll from plant leaves usually due to environmental or genetic factors.

Clippings: Leaf blades and, in some cases, stems and sheaths, cut off by mowing. Decompose readily due to their relatively high water content and generally simple chemical compounds.

Cool-season turfgrass: Turfgrass species whose growth is favored during the cooler portions (60º - 75ºF) of the growing season (spring and fall); may become dormant, injured or even killed during hot, dry weather.

Compaction (of soil): Increase in soil density through destruction of its pore space, as by excessive traffic or working the soil especially when its wet. Can be hard and almost impenetrable when dry.

Complete fertilizer: Any fertilizer product containing at least nitrogen, phosphorus, and potassium.

Complete metamorphosis: An insect life cycle going through the 4 distinct stages of egg, larva, pupa and adult. The larva stages include several important turfgrass pests associated with caterpillars, grubs and maggots.

Compost: Partially to completely decomposed organic materials. It is typically made by piling a mixture of grass clippings, leaves, etc., in a mound and, periodically stirring and mixing the pile hastening the decomposition process.

Contact herbicide: A weed killer that kills primarily by contact with plant tissues.

Creeping growth habit: Stem growth at or near the soil surface with lateral spreading by rhizomes and/or stolons.

Crown: A tightly compressed stem-like structure or growing point that pushes new leaves upward as they form and grow. In lawn grasses it is located at the base of the plant at or near the soil line. The location of the crown allows regular mowing to be done while not compromising the plants ability to regrow.

Cultivar: 'Cultivated variety' A group of cultivated plants distinguished by various features such as growth habit or leaf form that, when reproduced through seed or vegetative means, retain their distinguishing features.

Cultivation: As applied to lawns, cultivation means working the soil and/or thatch without destroying the entire lawn surface; examples of cultivation include coring, slicing, spiking.

Cultural Control: The practice of modifying a growing environment to reduce the prevalence of pests. Examples include changing irrigation methods or selecting resistant plants.

Cultural practices: Various horticultural methods and techniques used to care for plants in the yard and garden. Examples include watering, fertilizing, mowing, mulching, weeding, and edging.

Damage threshold level: The lowest amount of a pest population where unacceptable levels of damage occur. Used - as part of an integrated pest management plan - to determine when, if any, pesticides are applied to control a pest population.

Decomposition: The rotting or decaying of a organic substance.

Deficiency (of nutrients): Growth symptoms (such as chlorosis) caused by inadequate supply or unavailability of plant nutrients.

Dichlorophenoxyacetic acid (2,4-D): An growth regulator type of weed killer often used for controlling broadleaf weeds in lawn areas. See phenoxy herbicides.

Dicot (short for Dicotyledonae): Plant having two cotyledons (first leaves to appear as the plant emerges from the seed) and broad, net-veined leaves usually associated with broadleaf plant species.

Disease: An interaction between a grass plant, pathogen and its environment that results in abnormal growth and/or appearance.

Dormant turfgrass: Grasses that have temporarily ceased growth as a result of extended drought, heat or cold stress, but are capable of reinitiating growth when environmental conditions are favorable.

Drop Spreader: A spreader, used in the application of fertilizer or seeding, that distributes the material directly below the spreader through a series of small openings located at the base of the hopper. It is slower to use but can provide very precise application. Sometimes known as a gravity spreader.

Drought: Extended periods of dry weather often causing moderate to severe stress in turf. It can be particularly damaging when combined with high temperatures.

Drought tolerance: The grass plant's ability to withstand extended periods of dry conditions with incurring permanent damage. See also tolerance.

Ecosystem (turfgrass): The interaction of a turfgrass community with other plants, animals and their surrounding environment.

Endophyte: A plant living and functioning within another plant. For example, a fungus.

Environment: The sum of all the physical, chemical and biological components to which an organism is subjected. Soil, water, air, plants, animals, and human beings comprise the environment to which turfgrass communities are subjected.

Eradicate: To completely eliminate something from an area or the environment.

Erosion: The wearing away and transport of soil from land areas by wind or running water.

Establishment, turf: Continual root and shoot growth following seed germination, sodding or sprigging needed to form a mature turf area.

Ester: A phenoxy herbicide formulation that is more prone to vaporizing and potentially moving off-site than the amine form.

Evaporation: Water loss back to the atmosphere through the vaporization of water.

Evapotranspiration: Total loss of moisture through evaporation and transpiration.

Fertilizer: Nutrient supplements that stimulate and maintain healthy plant growth. The most common nutrients contained in fertilizers are nitrogen, phosphorus, and potassium.

Fertilizer analysis: The amount of each nutrient in a fertilizer container expressed as percent of the total weight.

Fertilizer burn (foliar burn): Plant injury (and usually death) caused by desiccation of tissue due to contact with high concentrations of certain fertilizers.

Fertilization: The proper application a fertilizer product to suppliment soil nutrients available to plants.

Fibrous roots: Profusely branched roots consisting of many lateral rootlets and usually no main or taproot development.

Foliar Fertilizing: A technique of feeding plants by applying liquid fertilizer directly to plant leaves.

Footprinting, wilt: During periods of mild to moderate stages of water (drought) stress, grass plants may be slow to spring back after walking on them leaving temporary foot-shaped impressions on the lawn.

Footprinting, frost: Discolored foot-shaped areas of dead leaf tissue created by walking on live, frosted grass leaves.

Fungi: Organisms which live off dead or living plants or animals.

Fungicide: A pesticide used to destroy or suppress fungi.

Fungus: (pl. fungi) A non-vascular (i.e., plants that do not contain water and nutrient conducting vessels) plant that lacks chlorophyll. Some examples are: mushrooms, molds, rusts, and yeasts.

Germination: Sprouting of the root and shoot from a seed when environmental conditions are favorable.

Granular: Pesticide or fertilizer formulations in which the active ingredient or nutrient is attached to small, dry particles of some inert carrier such as clay or ground corn cobs.

Grass: A common name for members of the Grass (Gramineae) family of plants.

Grass-cycling: The process of allowing grass clippings to remain on the lawn and decompose naturally, returning nutrients to the soil.

Grassy weeds: Weeds such as crabgrass, foxtail and goose grass create an uneven look to lawns and take resources from the desirable grass.

Groundcover: A horticultural term applied to low-growing vegetation covering the ground; usually refers to broad-leaf plants rather than lawn grasses.

Groundwater: Underground water found in porous rock strata or soils.

Grubs: The larval forms of beetles, grubs live in the soil and feed on plant roots. A grub-damaged lawn usually shows large, irregular sections of brown turf that detach easily from the soil. Grubs are most effectively treated in late summer or early fall, before they mature.

Guaranteed analysis: The guaranteed minimum amount of plant nutrients contained in a fertilizer product.

Hardiness: The genetic capability of a plant to adapt and survive the rigors of a particular climate, particularly to cold temperature stress.

Hardening-off (conditioning): The process of conditioning plants to more stressful environmental conditions.

Heavy Soil: A soil that contains a high proportion of clay and is poorly drained.

Herbicide: A specific category of pesticides used for controlling weeds.

High-maintenance lawn: Lawn areas composed of grass species and varieties requiring higher levels of water, fertilizing and mowing to remain healthy.

Host plant: Any plant that provides nutrition (and possibly shelter) for a plant pest to survive. That is, any plant that an insect or pathogen lives on is a host plant.

Impervious (surfaces): Waterproof coverings that do not permit infiltration of water and that increase the volume and speed of runoff water. Examples include: roofs, parking lots, roads and driveways.

Incomplete metamorphosis: The life cycle of an insect going through the stages of egg and nymph to reach the adult stage. The nymph resembles the adult and progresses through several molts before reaching the adult stage. There is no pupa stage in this type of metamorphosis.

Inert: Not active.

Inert ingredients: Materials in a pesticide or fertilizer formulation that have no activity in creating the desired effect of the product. Many serve as binding agents or carriers for the active ingredients such that they can be applied efficiently and uniformly.

Infection: Establishment of a pathogen within a host plant.

Infiltration (water): The physical process of water movement into a soil.

Insecticide: A specific category of pesticides used for controlling insects.

Integrated pest management (IPM): IPM is a method that works to control pests by combining monitoring, cultural care, control products and proper plant selection.

Inorganic (fertilizer): Products used for supplying nutrients to a lawn; generally composed of simple, mostly water soluble nutrient salts that are immediately available for plant use following post-application watering.

Irrigation: The use of automated or manual systems for applying supplemental water for the benefit of growing plants and replenishing soil moisture.

Label: A printed statement attached to the pesticide or fertilizer container by the manufacturer listing the contents, directions for use, and precautions. A pesticide label is considered a legal document that is approved and registered by the U.S. Environmental Protection Agency and the State Department of Agriculture.

Larva: The immature or worm stage (e.g., caterpillars, maggots, and grubs) of an insect that goes through 4 distinct lifecycle stages (i.e., egg, larva, pupa, adult) in its development. (See complete metamorphosis.)

Lawn: That portion of a yard or land area covered with grass plants kept short through mowing.

Lawn grass (turfgrass): A species or cultivar of grass that is maintained at a desired height through regular mowing.

Leaching: The downward movement in water of pesticides and/or nutrients through the soil column.

Liquid fertilization: A method of applying plant nutrients as a solution of dissolved fertilizer salts.

Low-maintenance lawn: Lawn areas composed of turfgrass species and varieties tolerant of reduced levels of water, fertilizer and mowing while still remaining healthy.

Metamorphosis: A basic change in form; for example, the changing of a grub to an adult beetle or caterpillar into an adult butterfly.

Microbial: Effects associated with the action or influence of microorganisms.

Micronutrients: Essential nutrients needed in tiny amounts for healthy plant growth.

Microorganisms: Living plants or animals (such as bacteria, fungi, or protozoa) that are so small they can be seen only with the aid of a microscope.

Minerals: The inorganic materials that make up a portion of the soil derived from rocks; they are usually of specific composition and crystalline in form.

Mixture (seed blend): As applied to turfgrasses, it is a combination of two or more plant species. For example, a mixture of Kentucky bluegrass and fine-leaved fescue seed.

Moles: Small mammals that dig tunnels that cause unsightly trails on the surface of the lawn and disrupt the root system.

Molt: To shed or cast off (such as skin, hair or feathers) followed by replacement through continued growth. Molting is often associated with the changes from immature to mature stages among the various insect groups.

Monocot (short for Monocotyledonae): A class of seed plants distinguished by such plant features as narrow, parallel-veined leaves, fibrous root systems, seeds containing only one cotyledon (seed leaf). Grass plants are a common example.

Mowing: The periodic and usually regular cutting of a lawn area to a specified height for its intended use and function. Accomplished with mowers, either manual or power operated.

Mulch: Non-living material used to cover the soil surface for purposes of controlling weeds, conserving moisture, reducing soil temperatures, and improving appearance. Examples are woodchips, compost, and leaves.

Mulching mower: Mowers specifically designed to finely chop grass clippings and forcibly direct them back into the lawn leaving a clean, uniform appearance to the surface.

Natural: The world of living things, material objects, and the forces and process which guide and shape living and nonliving things.

Natural growth cycle (turf): The sequence of grass root, shoot and flowering growth phases that occur naturally over the course of a growing season.

Natural organic nitrogen fertilizer: A fertilizer product containing plant nutrients derived from various organic sources as contrasted with simpler inorganic sources. Common sources include composts, sludges, animal manures and various plant and animal processing by-products.

Net weight (fertilizers): The actual weight of only the fertilizer nutrients contained in a package of fertilizer.

Nitrogen: An essential nutrient required for plant growth. It is a significant component of plant proteins. Adequate nitrogen produces good green color and vigorous plants. Shortages of nitrogen are usually indicated by yellowing leaves and poor growth. Excess nitrogen can result in unhealthy, lush growth making the plants more vulnerable to environmental stresses such as heat, drought, frost and, increased disease susceptibility.

Non-selective: A term applied to a category of herbicides that does not discriminate in its effect on one type of plant over another. For example, both grasses and broadleaf plants would be injured or killed as opposed to selectively killing broadleaf plants without affecting the grasses in a lawn area.

Nontarget organism: Plants (or other organisms) other than those attempted to be controlled by an application of a pesticide.

Noxious (weed): Any plant declared by a state authority to be so objectionable that efforts will be directed at its eradication.

N-P-K: Chemical symbols for nitrogen (N), phosphorus (P) and potassium (K). On a container of fertilizer, these nutrients are always expressed as percentages contained in the package and are always shown in the order N-P-K.

Nutrients (plant): Mineral elements considered essential for plant growth. There are presently 16 minerals known to play essential roles in plant nutrition.

Nutrient release rate: The speed at which plant nutrients, especially N, become available for plant use following application to a lawn. This rate is often determined by the product, water and temperature conditions at the time of application.

Nymph: The immature stage between the egg and adult of some insect groups; nymphs look like the mature adult in form but do not have fully developed wings and are not able to reproduce.

Organic: Chemical compounds containing the element carbon other than the inorganic carbonates. Often refers to any part of, or anything produced by, plants or animals.

Organic matter (soil): A portion of the soil consisting of substances derived from the life and death of plants, plant parts and other soil organisms.

Overseeding: Seeding onto an existing lawn for the purpose of lawn repair, introduction of different grass species, or provide a green cover to dormant warm-season lawns.

Patch disease: A non-specific term applied to small dead, circular areas in a lawn caused by a number of different pathogens. Symptoms may also include the appearance of dead rings of grass with green grass inside and outside of the ring.

Pathogen (plant): Usually applied to a microorganism with the capacity to cause a plant disease.

Perennial: Plants that live two or more years producing flowers and seeds in successive years.

Permeable: Allowing water or other substances to pass through or infiltrate (e.g., a permeable surface such as a lawn).

Pest (plant): Any insect, mite, rodent, nematode, fungus, weed, or other organism capable of causing plant stress, injury or death through disease, consumption of the plant or competition.

Pesticide: Any chemical (or mixture of chemicals) or biological agent used to control plant or animal pests in order to protect and/or preserve desirable plants.

pH level: This indicates the acidity or alkalinity of the soil. A pH value of 7.0 is neutral. Values less than this are acidic, while values greater are alkaline.

Phenoxy-type herbicides: A category of systemic weed killers that have a chemical structure composed of six carbon atoms joined together in a ring formation. Two examples are 2,4-D and mecoprop (MCPP).

Phosphorous: One of the major plant nutrients; important in root growth and plant energy functions. The middle number of a fertilizer analysis N-P-K.

Photosynthesis: The chemical plant process where carbohydrates are formed by combining carbon dioxide and water in the presence of light; occurs in the chlorophyll containing parts of the plant (i.e., leaves and stems).

Plant competition: The interaction between plants for light, moisture, and soil nutrients.

Postemergence: Generally refers to the application of an herbicide after the weed has emerged (and is usually visible) from the soil.

Potassium: One of the major plant nutrients important in maintaining general plant health and vigor. Often associated with improved stress and disease tolerance. It is the third number in the fertilizer analysis N-P-K. See N-P-K.

Preemergence: Generally refers to the application of an herbicide before the weed emerges from the soil. Target plants are most often not visible above ground at the time of application.

Pre-emergent weed control: A treatment used to prevent the appearance of weeds such as crabgrass.

Pupa: The resting or transforming stage of an insect that goes through four lifecycle stages (i.e., egg, larva, pupa, adult) in its development.

Pure live seed (PLS): A seed lot's percentage of seed that is pure and viable.

Quick-release nitrogen source: Nitrogen from these sources is available for use by the plant as soon as water is applied and the fertilizer granule dissolves. Can also be applied in liquid formulations. Plant responds with quick green-up and rapid rates of growth.

Reel mower: A mower that cuts grass by means of a rotating reel of helical blades passing over a fixed blade (called a bedknife) attached to the mower frame. Very uniform, clean cuts can be made with this type of mower.

Renovation, turf: Improving a stand of turf through replanting into an existing lawn area.

Rhizome: An elongated underground stem with scale-like leaves and adventitious roots originating from the nodes (bud containing areas along a stem).

Rhizomatous: A spreading growth habit resulting from the production and elongation of rhizomes.

Root: The fibrous, underground part of a plant associated with mineral and water absorption.

Root zone: That portion of the soil column occupied by plant roots.

Rotary mower: A mower that cuts turf by a high-speed impact of a rotating metal blade positioned parallel to and at a desired height above the lawn surface.

Rotary spreader: A spreader, most often used in the application of fertilizer, that distributes the material in an arc, several feet wide, by means of a rotating disc below the fertilizer hopper. It is able to cover large areas quickly, but distribution may not be precise enough for some applications.

Rototilling: The process of working (tilling) the soil utilizing a machine known as a rototiller. The machine utilizes a series of vertically rotating tines (blades) mounted on either the front or rear of the machine. It is capable of penetrating 6 to 8 inches into the soil.

Scalping: An undesirable mowing practice that removes an excessive amount of green leaves and shoots at any one mowing. It can seriously weaken or even kill the turfgrass.

Seed: A ripened ovule, containing an embryo or rudimentary plant capable of producing a new plant.

Seed count: The actual number of seeds of a particular species or variety contained in a seed blend or mixture.

Seed weight: The actual weight of seeds from a particular species or variety contained in seed blend or mixture. Expressed as a percent of the total weight.

Seeding: The process of distributing seed over the soil surface, either mechanically or by hand, in an attempt to establish a new lawn or renovate an existing lawn.

Selective (herbicide): The term usually applied to an herbicide that has the ability to only destroy one type of plant while not affecting others. For example, a postemergence, broadleaf herbicide will kill broadleaf plants (such as dandelions) in the lawn without affecting the grass plants.

Shade: An area of reduced light quantity (and often quality) resulting from the partial or complete obstruction of direct sunlight.

Sheath: The tube shaped, basal section of the grass leaf enclosing the stem.

Shoot: Above ground, vertically oriented growth giving rise to both leafy growth and flowering stems (culms).

Shoot density: The number of shoots contained in a specified area of lawn.

Slit-seeding: The use of a machine known as a slit-seeder to seed a new lawn area or overseed an existing area. Slit-seeders utilize a series of vertically rotating discs to cut small grooves into the soil while depositing seed into the grooves just behind the discs. It is an excellent means of seeding and helps insure the seed-to-soil contact necessary for successful establishment.

Sloughing-off: The periodic shedding of plant parts. As used here, it refers to the periodic shedding of turfgrass roots as either part of the natural growth cycle, or as a result of environmental stresses.

Slow-release nitrogen source: Nitrogen from these sources becomes available as the product is broken down by soil microbes and/or chemical action. Plant responds with a slightly slower rate of green-up and growth. Usually this is a desirable characteristic.

Sod: Squares or strips (rolls) of turfgrass cut from a production field and usually with a thin layer of soil still attached that is used for vegetatively installing a turfgrass area.

Sod cutter: An machine or hand tool that is designed to cut the grass plus a thin layer of soil from the ground. The length and thickness of the cut sod can be varied.

Sodding: Installing a turfgrass area utilizing sod.

Soil: The earth's thin upper layer capable of supporting plant growth. It is characterized by such things as texture, structure, color, and fertility which distinguishes it from material like gravel, sand or bedrock that also cover a portion of the earth's surface.

Soil Amendment: Any substance added to the soil for the purpose of improving the quality of the soil.

Soil structure: The combining of microscopic soil particles through the action of soil microbes into larger units commonly known as soil granules, crumbs or aggregates. Loose, crumbly soil structure is a must to sustain health plant growth.

Soil test: A scientific analysis of a soil sample that determines its pH, texture, organic matter content and various degrees of chemical composition. They are used to assess a soil's suitability for particular uses and any necessary modifications to prepare it for the intended use.

Soluble (fertilizer): Fertilizers that are made up of easily dissolved components in water which are immediately available for plant use; they can result in lawn "burning" more easily that slow-release fertilizers.

Species: A basic identification unit used in biology to describe a single distinct kind of plant or animal that has certain distinguishing characteristics separating it from all others.

Spot treatment: Generally refers to the application of a pesticide to a limited or small area. In the case of herbicides, it may also be applied to the treating of individual plants.

Spreader: A piece of equipment used for seeding and fertilizing. It may be machine driven, pushed by hand or hand-held.

Stem: The horizontal or vertical axis of a plant supporting leaves, buds and flowers.

Stolon: An elongated stem growing along the ground surface and giving rise to leaves and adventitious roots at the nodes (bud containing areas along a stem).

Stoloniferous: A spreading growth habit resulting from the production and elongation of stolons.

Storm sewer system: A system of ground level inlets (usually covered with some type of steel grate) designed to intercept storm water runoff from the adjacent land areas and channel it below ground to a system of interconnected pipes that eventually empty into wetlands, lakes, rivers, streams or other designated storm water holding areas.

Storm water runoff: Rain water that cannot soak into soil and runs over surfaces such as streets, driveways and rooftops. Storm water runoff picks up pollutants as it moves.

Stress (plant): Usually applied to environmental factors restricting normal or healthy plant growth. Some of these factors are heat, drought, compacted soils, water-logging and cold.

Summer dormancy: Growth stoppage and subsequent death of leaf tissue of certain cool-season grass species due to heat and/or moisture stress. Except in extreme conditions, the crown remains alive and begins regrowth when favorable growing conditions return.

Sustainable (lawn): A lawn area requiring few outside inputs (e.g., pesticides) to maintain healthy grass while having a positive impact on the environment.

Synthetic organic nitrogen fertilizer: Generally refers to fertilizers formed when urea, a quick-release N fertilizer source, is further processed or combined with other materials to give it a slow-release rate characteristic.

Texture (grass): The coarseness or fineness of a turfgrass generally based on the grass blade width and the stem size.

Texture (soil): The relative proportion (expressed as a percent) of sand, silt, and clay particles in a soil; determines soil coarseness or fineness.

Thatch: A natural layer of plant material made up of dead grass (roots, stems, leaves) that can be harmful to a lawn if allowed to become too thick. Thatch is not caused by leaving grass clippings on the lawn (grasscycling).

Tilth: Describes the general health of the soil. Soil that is healthy and has good physical qualities is said to be in good tilth.

Tiller: A lateral shoot, usually erect, that develops from axillary buds in the crown.

Tolerance: The plant's ability to withstand stresses associated with unfavorable environmental conditions or the application of pesticides.

Topsoil: The upper portion of soil that is generally higher in organic matter in comparison to the subsoil and usually has more favorable characteristics of soil fertility, aeration and structure.

Transpiration: Water loss that occurs through the open plant stomata (tiny pores primarily on the underside of the leaf). Rate of loss is determined by wind and atmospheric humidity conditions.

Turf: A soil covering of mowed vegetation, usually a turfgrass.

Urea: A quick-release nitrogen fertilizer source. Usually available as 45-0-0 or 46-0-0. It is also described as a synthetic organic fertilizer as it contains the element carbon in its chemical structure.

Variety: A population of plants having many characteristics in common; a variety may be a pure line, a mixture of pure lines, or a clone.

Vertical mower: A machine with high-speed, vertically rotating blades that slice into the turf for the purpose of reducing thatch or improving soil aeration.

Vigor (plant): The combination of genetic and environmental factors that determine the rate and amount that a turfgrass species or cultivar is able to grow and spread.

Warm-season turfgrass: Turfgrass species whose optimum growth occurs during the warmer periods (80º - 95º F) of the growing season.

Water insoluble nitrogen (WIN): That fraction of nitrogen contained in fertilizer not considered to soluble in 25o C. water. It is generally a measure of how much of the nitrogen is considered to show the slow release characteristic.

Water soluble nitrogen (WSN): That fraction of nitrogen contained in fertilizer considered to be soluble in 25o C. water. It is generally a measure of the quick-release nitrogen contained in the fertilizer. Unlike WIN this is usually not expressed on a fertilizer package. Unless stated otherwise, the difference between the WIN and total nitrogen contained in the package is WSN.

Watering-in: Water applied to turf immediately after the application of some pesticides or fertilizers to dissolve and/or move materials into the soil.

Waterlogging: Soil saturated with water usually for an extended period of time and resulting in temporary anaerobic conditions.

Wear: The accumulative (and usually deleterious) effects of traffic on a turf area. Most often a problem on sports fields.

Weed: An undesired, uncultivated plant growing where it is not wanted and in a manner so as to adversely compete with desirable plants for water, light and nutrients, or destroy aesthetic qualities of a lawn.

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