[invasive.org] Description, Ecological threat: Appearance Taraxacum officinale is a perennial that grows best in moist areas in full sun. Its strong taproot is capable of penetrating the soil to a depth of 10 to 15 ft. (3 to 4.6 m), but it is most commonly 6 to 18 in. (15.2 to 45.7 cm) deep. Foliage Leaves are clustered in a rosette at the base of the plant. Leaves vary in length from 2 to 14 in. (5.1 to 35.6 cm) and from 0.5 to 3 in. (1.3 to 7.6 cm) wide. Margins of the leaves are deeply serrated. Flowers Flowering stalks are 6 to 24 in. (15.2 to 61 cm) in length and terminate in a compound inflorescence or head that contains 100 to 300 ray flowers and looks like a characteristic puffball. Each ray flower has a strap-shaped yellow petal with five notches at the tip. Taraxacum officinale flowers are not normally pollinated but develop asexually. The seeds are achenes and are about 0.13 in. (0.32 cm) in length with five to eight ribs. Ecological Threat Taraxacum officinale can be a major weed problem for turf and ornamental managers. In turf, it forms clumps that cause poor footing for athletic fields and golf courses. When this plant infests turfgrass and ornamental plantings, it forms dense circular mats of leaves that crowd out desirable species and reduce the vigor of those plants that survive. (link added by Mary Ann Machi)