Diodia teres Walt. - Rough Buttonweed

Diodia teres plant

Family - Rubiaceae

Stems - Erect to prostrate, +20cm tall, herbaceous, 4-angled, variously pubescent, reddish with age and in strong sun, from taproot.

Leaves - Opposite, sessile, entire to denticulate, linear to linear-lanceolate, variously pubescent, to 5cm long, 6mm broad, acute to aristate. Stipule (membrane) connecting leaf bases with reddish erect capillary bristles.

Diodia teres bristlesBristles of stipules.

Inflorescence - Axillary clusters of 1 to 3 sessile flowers.

Flowers - Corolla lilac to whitish, 4-lobed, funnelform, 4-6mm long, pubescent externally. Lobes acute to aristulate. Stamens 4, adnate near apex of corolla tube, exserted (slightly). Anthers pale yellow to whitish. Stigma biglobose. Ovary inferior. Sepals 4, lanceolate, green, to 2mm long, persistent on fruit. Fruit pubescent, biglobose, splitting into 2 nutlets.

Diodia teres flowersFlower close-up.

Flowering - June - October.

Habitat - Waste ground, disturbed sites, gravel beds along streams, glades, prairies, pastures, railroads.

Origin - Native to U.S.

Other info. - This is a fairly common plant in the lower 2/3 of the state. It is capable of growing in some very inhospitable locations. The plant is easy to identify in the field because of its bluish flowers and long stipular bristles.

Photographs taken off Lee Rd 10, Auburn, Al., 9-29-04.


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