Melilotus albus Medik.

White Sweet Clover

Melilotus albus plant

Family - Fabaceae

Stems - To +2m tall, herbaceous, erect, branching, typically single from base, glabrous or with a few sparse hairs.

Leaves - Alternate, trifoliolate, stipulate. Stipules linear-attenuate, 4-5mm long, -1mm broad, glabrous. Petioles to +/-1cm long, glabrous or with a few sparse hairs, with an adaxial groove. Petiolules to 2mm long on lateral leaflets and 5-6mm long on terminal leaflet. Leaflets subequal (the terminal slightly larger), oblong to oblong-oblanceolate, serrate-dentate, glabrous, to +/-3cm long, +/-1cm broad.

Melilotus albus leafPressed leaf.

Inflorescence - Axillary pedunculate racemes to +/-8cm long(tall) in flower, longer in fruit. Axis sparsely pubescent. Each pedicel subtended by a linear-attenuate bract to 1mm long. Pedicels to 1.1mm long, mostly glabrous.

Flowers - Corolla white, papilionaceous, glabrous. Standard to 4mm long. The keel petals apically connate. The wing petals basally adnate to the keels, with basal auricles to .5mm long. Stamens diadelphous, white, glabrous. Anthers yellow, .2mm long. Style glabrous, +/-2mm long. Ovary green, glabrous, 1.1mm long. Fruits to 4-5mm long, inflated, with a short beak, glabrous, green. Calyx weakly bilabiate. Calyx tube green, to 1mm long, sparsely pubescent to glabrous. The upper lip 2-lobed. Lobes triangular-acuminate, 1mm long. The lower lip 3-lobed. The lobes slightly larger to equaling those of the upper lip.

Melilotus albus flowersFlowers close-up.

Flowering - May - October.

Habitat - Disturbed sites, waste ground, roadsides, railroads.

Origin - Native to Eurasia.

Other info. - This plant is extremely common and is very invasive. It was and is used for fodder because if its protein content. The plant has an undesirable smell (at least to me) when crushed or cut. Many people have reported headaches or nausea after being exposed to the smell of the freshly cut plants for too long. Plants from the genus Melilotus contain coumarins, which are used to make rat poisons.
This plant is very similar to M. officinalis but that species starts blooming a few weeks to a month earlier and has yellow flowers.

Photographs taken at Alley Spring, MO., 6-27-03 (DETenaglia); also at Busch Wildlife Area, St. Charles County, MO, 6-12-2009 (SRTurner).