This section is from the book "Nature's Garden", by Neltje Blanchan. Also available from Amazon: Nature's Garden; An Aid To Knowledge Of Our Wild Flowers And Their Insect Visitors.
Flowers - Bright yellow, papilionaceous, about 1/2 in. long, on short pedicels, in numerous- but few flowered terminal racemes. Calyx light green, 4 or 5-toothed; corolla of 5 oblong petals, the standard erect, the keel enclosing 10 incurved stamens and 1 pistil. Stem: Smooth, branched, 2 to 4 ft. high. Leaves: Compounded of 3 ovate leaflets. Fruit: A many-seeded round or egg-shaped pod tipped with the awl-shaped style.
Preferred Habitat - Dry, sandy soil.
Flowering Season - June - September.
Distribution - Maine and Minnesota to the Gulf States.
Dark grayish green, clover-like leaves, and small, bright yellow flowers growing in loose clusters at the ends of the branches of a bushy little plant, are so commonly met with they need little description. A relative, the true indigo-bearer, a native of Asia, once commonly grown in the Southern States when slavery made competition with Oriental labor possible, has locally escaped and become naturalized. But the false species, although, as Dr. Gray says, it yields "a poor sort of indigo," yields a most valuable medicine employed by the homoeopathists in malarial fevers. The plant turns black in drying. As in the case of other papilionaceous blossoms, bees are the visitors best adapted to fertilize the flowers. When we see the little, sleepy, dusky-winged butterfly (Thanaos brizo) around the plant we may know she is there only to lay eggs, that the larvae and caterpillars may find their favorite food at hand on waking into life.