Northern Prairie Wildlife Research Center
Smooth Buttonweed (Spermacoce glabra)
- Family: Madder (Rubiaceae)
- Flowering: June-October.
- Field Marks: This species is distinguished by clusters of small white flowers in the axils of the leaves and its smooth or slightly hairy stems and leaves.
- Habitat: Wet woods, around ponds and lakes, fallow fields, sloughs, along streams.
- Habit: Perennial herb with a woody root.
- Stems: Erect, usually branched, 4-sided, usually smooth, up to 2 feet long.
- Leaves: Opposite, simple, elliptic, pointed at the tip, tapering to the base, without teeth, finely hairy or smooth, up to 3 inches long, up to 1 inch broad.
- Flowers: Few to several in crowded, rounded clusters in the axils of the leaves; each flower white, 1/6-1/4 inch long.
- Sepals: 4, green, united at the base.
- Petals: 4, white, united below into a short tube.
- Stamens: 4, not exserted beyond the petals.
- Pistils: Ovary inferior, smooth.
- Fruits: Capsule splitting into two 1-seeded parts at maturity.
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