Scleranthus annuus L.

Knawel, German Knotgrass

Scleranthus annuus plant

Family - Caryophyllaceae

Stems - Multiple from the base, ascending, herbaceous, from a weak taproot. The horizontal portion of the stem with scarious scales. The erect flowering portion of the stem to +15cm tall, retrorse puberulent on half of the stem, sparsely pubescent on the other half, branching, terete.

Scleranthus annuus stemStem.

Leaves - Opposite, decussate, sessile, linear to subulate, entire, to +1cm long, 1mm broad, glabrous but ciliate-margined at the base. The bases of the opposite leaves connate, estipulate.

Inflorescence - Congested bracteate cymes or single axillary flowers. Flowers sessile. Bracts foliaceous.

Flowers - Petals absent. Sepals 5, green with lighter margins, lanceolate, to 3mm long, 1mm broad, glabrous. Hypanthium -2mm long, obconic. Stamens 5-10 (rarely less), erect, much shorter than the sepals. Filaments glabrous, .5mm long, broadened at the base and lining the edge of the hypanthium. Anthers bilobed, yellow, .2mm long and broad. Ovary green, superior, glabrous, 1mm long in flower. Styles 2, glabrous, 1mm long.

Scleranthus annuus flowerFlower.

Flowering - March - October.

Habitat - Glades, roadsides, railroads.

Origin - Native to Europe.

Other info. - This little species is easily overlooked in the field because of its small size and weedy habit. The green flowers are easily missed also. The plant is, however, easy to ID in the field because of its small size, linear leaves, and green flowers.
Steyermark reported the plant in just one county. Since that time it has been found in two more counties and its range almost certainly will increase in Missouri with time.
Below is a mature specimen:

Scleranthus annuus plant

Photographs taken in Brown Summit, NC., 4-13-03 and off Hwy 22 near Carthage, NC., 4-26-03.