RECUPERATIVE POTENTIAL. The ability of a turfgrass to recover from injury.

RELATIVE HUMIDITY.

= water vapour x 100 temperature ﾰC

RENOVATE. The improvement of a lawn without completely rebuilding.

RESIDUAL EFFECT. The ability of a pesticide to persist after application.

RESIDUE. The amount of pesticide present on or in a plant after application or exposure to the chemical, expressed on a ppm basis.

RESILIENCE. The ability of a grass leaf to return to an upright position after bending. A soil that has a cushiony feel to it, an important consideration in sports turf.

RESPIRATION. Metabolic oxidation.

RESTING SPORE. A thick walled spore that may remain viable for many months in a dormant state.

RHIZOME. An elongated, underground stem that grows horizontally, and is capable of producing a new plant.

ROGUING. The removal of undesirable plants from a monoculture.

ROOT ZONE. The area of soil where roots develop and grow.

ROSETTE. A cluster of closely crowded leaves, usually in a circular arrangement, arising from a very short stem near the ground.

RUST. A disease which is characterised by the appearance of reddish brown to golden yellow pustules on the plant surface.

RYEGRASS. Lolium species; annual (L. Multiflorum), and perennial (L. Perenne), cool season grasses used for many purposes.