Scleranthus annuus L.
Family: Caryophyllaceae
annual knawel,  more...
Scleranthus annuus image
Annual or biennial herb with a slender taproot to 15 cm tall Stem: low, diffusely forked, spreading, sometimes minutely hairy. Leaves: opposite, fused at the base, stalkless, 0.5 - 2.5 cm long, linear, one-veined. Inflorescence: a terminal and axillary, compact cluster (cyme) of flowers, subtended by paired bracts. Flowers: without petals, stalkless to nearly stalkless, hypanthium (a floral tube formed by the sepals and stamens) pitcher-shaped, abruptly expanded above. Stamens usually five to ten. Styles two. Sepals: five, distinct, greenish, equaling or longer than the hypanthium, lance-shaped with a more or less pointed tip, narrowly scarious-margined (dry, thin, and membranous) near the tip. Fruit: bladder-like, one-seeded (utricle), indehiscent, egg-shaped, enclosed in the persistent hypanthium. Seed yellowish, rounded.

Similar species: No information at this time.

Flowering: April to late November

Habitat and ecology: Introduced from Asia. An occasional weed of sandy, disturbed areas such as lawns, vacant lots, and nursery plots.

Occurence in the Chicago region: non-native

Etymology: Scleranthus comes from the Greek words skleros, meaning hard, and anthos, meaning flower, referring to the hardened flowers. Annuus means annual.

Author: The Morton Arboretum

Low, diffuse, spreading, glabrous or puberulent annual or biennial to 15 cm; lvs linear, the larger ones 5-25 mm; fls sessile or subsessile; sep equaling or longer than the hypanthium, lanceolate, ┬▒acute, with a very narrow scarious border (ca 0.1 mm wide) near the tip; stamens usually 5-10; 2n=22, 44. A weed in fields, roadsides, and waste places; native of Eurasia, established in our range from Que. to Wis., s. to S.C. and Mo. All summer.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.