Bean family (Fabaceae)
Description: This perennial wildflower is 1-2' tall, sending up one or more stems from the base that are unbranched or sparingly branched. The stems are light green, terete, and hairy. Alternate compound leaves are widely spreading; they are odd-pinnate with 9-25 leaflets. Individual leaflets are up to 1" long and ¼" across; they are medium green to grayish green, oblong to narrowly elliptic in shape, and smooth along their margins. Upper surfaces of the leaflets are hairless to silky-hairy, while their lower surfaces are pubescent to silky-hairy. Each leaflet has a prominent central vein. The central stalk (rachis) and petiole of each compound leaf is pubescent. At the base of each petiole, there is a pair of small stipules about ¼" long. The stems terminate in short dense racemes about 2-3" long that are covered in buds and bicolored flowers facing all directions. The racemes are held a little above the foliage on short peduncles. Individual flowers are ¾" long and across, consisting of 5 petals, a short tubular calyx with 5 teeth, 10 stamens, and a pistil. Each flower has a typical pea-like floral structure, consisting of an upright banner and a pair of lateral wings that project forward to enclose the keel. The broad banner is white to pale greenish yellow, while the wings are deep rosy pink. The pedicels of the flowers and their calyces are light green and pubescent. The blooming period occurs from early to mid-summer and lasts about 3 weeks. Afterwards, the flowers are replaced by widely spreading seedpods about 1½-3" long. These seedpods are initially light green, but later turn brown; they are silky-hairy. The seedpods are narrowly cylindrical and slightly flattened in shape; each pod contains several seeds that are reniform and somewhat flattened. The root system consists of a deep taproot.
Cultivation: The preference is full or partial sun, mesic to dry conditions, and an acidic sandy soil. Goat's Rue adds nitrogen to the soil.
Range & Habitat: The native Goat's Rue is occasional in all areas of Illinois, except the east-central section, where it is absent (see Distribution Map). Habitats include upland sand prairies, sandy hill prairies, sand dunes, upland sandy savannas, upland rocky savannas, and sandstone glades. In more wooded areas, Goat's Rue typically occurs where oaks are the dominant trees.
Faunal Associations: The nectar and pollen of the flowers attract leaf-cutting bees (Megachile spp., Hoplitis spp.) and possibly other long-tongued bees. The caterpillars of the skipper, Thorybes bathyllus (Southern Cloudywing), feed on the foliage of Goat's Rue and other species in the Bean family. Other insect feeders include caterpillars of the moth Semiothisa eremiata (Three-lined Angle), seed-eating larvae of two straight-snouted weevils (Apion segnipes, Apion perforicolle), the plant bug Teleorhinus tephrosicola, the blister beetle Epicauta murina, and several leaf beetles (Bassareus lituratus, Odontota horni, Odontota notata, Pachybrachis othonus, Phyllecthris gentilis). Among vertebrate animals, the seeds are eaten by the Wild Turkey, while cattle have been observed to browse on the foliage. The roots contain rotenone, which is toxic to insects and fish.
Photographic Location: The photograph of the flowering plant was taken by Keith & Patty Horn (Copyright © 2009) at a prairie in Fayette County, Illinois. The photograph of the plants with mature seedpods was taken by John Hilty at Hooper Branch Savanna Nature Preserve in Iroquois County, Illinois.
Comments: Because of its attractive bicolored flowers and widely spreading seedpods, Goat's Rue is fairly easy to identify. If only the foliage is present, then it is possible to confuse this wildflower with Amorpha canescens (Leadplant), Dalea foliosa (Leafy Prairie Clover), and possibly other species in the Bean family. These latter two species have very short seedpods and their flowers are much smaller in size than those of Goat's Rue. Across different populations of Goat's Rue, there is considerable variation in the hairiness of the foliage. Western populations that are found in sunny habitats often have leaflets that are densely covered with silky hairs, while eastern populations that occur in more shaded habitats have leaflets that are less conspicuously hairy.