Bermudagrass is mostly found in the southern half of the U.S. and in warm climates. It is fast growing and tough, making it popular and useful for sports fields, as when damaged it will recover quickly. It is a highly desirable turf grass in warm temperate climates, particularly for those regions where its heat and drought tolerance enable it to survive where few other grasses do. It has a relatively coarse-bladed form with numerous cultivars selected for different turf requirements. It is also highly aggressive, crowding out most other grasses and invading other habitats, and has become an invasive species in some areas. rThe blades are a grey-green color and are short, usually 2‚Äì15 centimeters (0.79‚Äì5.9 in) long with rough edges. The erect stems can grow 1‚Äì30 centimeters (0.39‚Äì12 in) tall. The stems are slightly flattened, often tinged purple in colour. The seed heads are produced in a cluster of 2‚Äì6 spikes together at the top of the stem, each spike 2‚Äì5 centimeters (0.79‚Äì2.0 in) long. It has a deep root system; in drought situations with penetrable soil, the root system can grow to over 2 m deep, though most of the root mass is less than 60 cm under the surface. The grass creeps along the ground and root wherever a node touches the ground, forming a dense mat. rBermudagrass reproduces through seeds, through runners and rhizomes. Growth begins at temperatures above 15 ¬∞C (59 ¬∞F) with optimum growth between 24 to 37 ¬∞C (75 to 99 ¬∞F); in winter the grass becomes dormant and turns brown. Growth is promoted by full sun and retarded by full shade, e.g., close to tree trunks.