IUCN threat status:

Not evaluated

Comprehensive Description

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Description

This introduced annual or biennial plant is 2-7' tall. Larger plants branch frequently and are somewhat bushy in appearance, while shorter plants are less branched and rather lanky. The stems are usually more or less erect, although sometimes they sprawl across the ground. They are glabrous, furrowed, and angular; sometimes the lower stems are ribbed light red. The alternate compound leaves are trifoliate and hairless. Each leaflet is about ¾" long and ¼" across; it is oblong, oblanceolate, or obovate in shape, and dentate along the middle or upper margin. The terminal leaflet has a short petiolule (stalk at its base), while the lateral leaflets are nearly sessile. The petiole of each compound leaf is about ½" long; there are a pair of small linear stipules at its base. Spike-like racemes of yellow flowers are abundantly produced from the axils of the middle to upper leaves, while the upper stems eventually terminate in such racemes. Each raceme is up to 6" long and has dozens of flowers. These flowers are loosely arranged along the raceme and somewhat drooping. They may occur along one or two sides of the raceme, or in whorls.  Each flower is about 1/3" long and has a tendency to droop downward from the raceme, although curving upward toward its tip. The corolla has 5 yellow petals and is rather slender, consisting of a standard, keel, and two side petals. The tubular calyx is light green and has 5 pointed teeth. The blooming period can occur from late spring to early fall, peaking during early to mid-summer; a colony of plants will bloom for about 2 months. There is a mild floral fragrance. Each flower is replaced by a small seedpod with a beak that is flattened and contains 1-2 seeds. There are usually transverse ridges on each side that are somewhat curved. The tannish yellow seeds are somewhat flattened and ovoid-reniform in shape. Yellow Sweet Clover spreads by reseeding itself, and it often forms colonies at favorable sites. The sweet hay-like aroma of the foliage is caused by coumarin.

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© John Hilty

Source: Illinois Wildflowers

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