Palmate
Palmate is used to describe both compound leaves and leaf venation. A palmate leaf is a compound leaf with four or more leaflets attached to the petiole at one location. Leaves with palmate venation have the main veins arising from the base of the leaf where it joins the petiole. A leaf with palmate venation may be either lobed or unlobed.
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Panicle
Seedhead in which the side branches are attached to the main axis with a stalk. May form a triangular shape.
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Parallel
Leaf veins begin at the base of the leaf and run lengthwise along the whole leaf.
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Parts Per Million (PPM)
The number of parts by weight or volume of a constituent in 1,000,000 parts of the final mixture, by weight or volume.
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Patches
Localized areas of diseased turf that are irregularly shaped and greater than 4 inches in diameter.
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Pathogen
The causal agent of disease.
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Perennial Plant
A plant that may or may not start from seed, may or may not produce seed, and lives more than two years.
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Pest
An organism which is destructive or harmful to the crop (in this case, turfgrass). Major types of pests include diseases (fungi), insects, nematodes, and weeds. Moles, voles, millipedes, mites, earthworms, and even crayfish can sometimes be considered pests of turfgrass.
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Pesticide
A chemical which kills pests. Pesticides include fungicides, herbicides, insecticides, and nematicides.
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PGR (Plant Growth Regulator)
Plant growth regulators (PGRs) are chemicals which control some aspect of plant growth or development. In turf, these chemicals are used to suppress foliar growth or seedhead development. PGRs include ethephon (Ethephon and Proxy), flurprimidol (Cutless), maleic hydrazide (Retard, Royal Slo-Glo, and Liquid Growth Retardant), mefluidide (Embark), metsulfuron methyl (Escort), paclobutrazol (TGR Turf Enhancer and Trimmit), and trinexapac-ethyl (Governor and Primo Maxx).
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Phytotoxic
Poisonous to plants.
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Pinnate
Pinnate is used to describe both compound leaves and leaf venation. A pinnate leaf is a compound leaf which has leaflets arranged along the sides of a common axis; feather-like. There is sometimes a terminal leaflet at the end of the central axis. A leaf or leaflet with pinnate venation has veins arranged in pairs on either side of a central midrib vein. A leaf with pinnate venation may be either lobed or unlobed. The trifoliate leaf shown in the middle photograph below is a pinnate leaf with pinnate venation.
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Plant Growth Regulator
Plant growth regulators (PGRs) are chemicals which control some aspect of plant growth or development. In turf, these chemicals are used to suppress foliar growth or seedhead development. PGRs include ethephon (Ethephon and Proxy), flurprimidol (Cutless), maleic hydrazide (Retard, Royal Slo-Glo, and Liquid Growth Retardant), mefluidide (Embark), metsulfuron methyl (Escort), paclobutrazol (TGR Turf Enhancer and Trimmit), and trinexapac-ethyl (Governor and Primo Maxx).
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Plant Growth Regulator (PGR) Herbicide (Herbicide, Plant Growth Regulator (PGR))
This class of herbicides is used on more land area worldwide than any other herbicide group. The mode of action is not well understood, but in general they interfere with plant metabolism and transport. In turf, they are 2,4-D, 2,4-DB, clopyralid (Lontrel), triclopyr (Turflon Ester), and dicamba (Banvel).
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Postemergence (POST) Herbicide (Herbicide, Postemergence (POST))
Herbicide that needs to be applied after weeds emerge in order to be effective.
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Postemergence Herbicide (Herbicide, Postemergence (POST))
Herbicide that needs to be applied after weeds emerge in order to be effective.
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Power Raking (Raking, Power)
Removal of debris with rapidly rotating vertical tines or brush.
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Preemergence (PRE) Herbicide (Herbicide, Preemergence (PRE))
Herbicide that needs to be applied prior to weed emergence in order to be effective. Can be applied before or after turf establishment. Rainfall or irrigation is often needed to move the chemical into the top few inches of the soil for best activity.
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Preemergence Herbicide (Herbicide, Preemergence (PRE))
Herbicide that needs to be applied prior to weed emergence in order to be effective. Can be applied before or after turf establishment. Rainfall or irrigation is often needed to move the chemical into the top few inches of the soil for best activity.
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Prophyll
The first leaf of a branch off the main axis; a sheath-like structure.
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Prostrate
Low growing; hugging the ground.
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PSI
Pounds per square inch.
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Puffballs
A spherical spore-producing structure up to 3" in diameter produced on the turf surface. This fungal symptom is similar to a mushroom, but lacking a stem or stalk.
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Puffiness
A spongy, irregular surface.
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Pustules
Small, spherical structures containing fungal spores which are produced on diseased leaf surfaces.
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Quick Release Nitrogen (Nitrogen)
Nitrogen is the most important element in turfgrass culture. It is required for the formation of chlorophyll which is then used for photosynthesis. Nitrogen is also found in numerous plant proteins, amino acids, enzymes, and vitamins. Nitrogen is primarily absorded through the roots in the nitrate (NO3-) form, but can also be taken up in the ammonia form (NH4+). Nitrogen rich fertilizers are often used to enhance and maintain turf appearance (green color) and density.
Nitrogen sources are normally referred to as quick release and slow release.
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Quick release sources (e.g., ammonium nitrate) are water-soluable and produce fast turf greening. These sources have a short residual and a high burn potential.
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Slow release sources of nitrogen (e.g., IBDU, Urea formaldehyde) are typically organic materials broken down over time by soil microorganisms. These materials produce slow slow turf green-up, have a long residual, and low burn potential.
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Raceme
Seedhead in which more than one slender spike is attached along the end of the stem. Individual spikes can be attached at one point or along the top of the stem in an alternate fashion.
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Raking, Power
Removal of debris with rapidly rotating vertical tines or brush.
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Resistance
Resistance is the inherited ability of an organism (turfgrass, weed, disease, insect, etc.) to survive exposure to a dose of pesticide (herbicide, fungicide, insecticide, etc.) normally lethal to the wild type of the organism. Continual use of pesticides with similar control mechanisms (modes of action) can result in pests that are resistant to some chemicals. Poor or ineffective pest control can be expected when this occurs. Managers can reduce the chances of this happening by mixing or alternating pesticides belonging to different chemical classes.
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Rhizome
An underground creeping stem which can produce roots and shoots at each node.
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Rings
Circular areas of diseased turf with healthy turf to the inside and outside, leaving a ring-like pattern on the turf stand.
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Rosette
A cluster of leaves radiating out from a central axis.
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Rush
Rushes are upright plants of the Juncaceae family. Like grasses and sedges, they have fibrous roots. Rushes have round, solid stems. Like sedges, their leaves are borne in groups of three. Leaves are either alternate or basal, parallel veined, and are much longer than they are wide. Rushes are considered semi-aquatic, and like sedges, will be found where there is an abundance of water. Rush flowers are solitary and arranged in heads, making them distinctly different from both grasses and sedges.
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