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.

Carbohydrate – Chemical compounds composed of carbon, hydrogen, and oxygen. Examples include starch, sugar, and cellulose.

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.

Competition – The other guys are ready to eat you for lunch.

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.

Crop – In this definition, crop refers to percent by weight of all seeds contained in a seed package normally considered to be grown as an agriculture crop, including hay.

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.

Cultipacker Seeder – A mechanical seeder that prepares the seedbed just ahead of placing the seeds at a shallow depth followed by firming the soil around the seed. This is a rather large unit adapted for use as a tractor pull-behind or rear-mounted unit.

Cultivar – 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 turf, cultivation means working the soil and/or thatch without destroying the entire lawn surface; examples of cultivation include coring, slicing, spiking.

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

Damage Threshold Level – The lowest amount of a pest population where unacceptable levels of damage occur. Used 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) – A 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 – A condition of significantly reduced activity where little if any growth occurs and where rates of physiological activities, like photosynthesis, are minimal or non-existent.

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.