Naked-Flowered Tick Trefoil
Desmodium nudiflorum
Bean family (Fabaceae)

Description: This perennial wildflower consists of a short leafy stem (4-12" tall) and a flowering stalk (1-3' long) that are separated from each other at the base. The leafy stem is erect, light green to reddish green, and short-pubescent; it has 1-2 pseudo-whorls of 3 compound leaves at its apex. The compound leaves are trifoliate with slender petioles about 2-3" long. Individual leaflets are 2-3" long and 1-2" across; they are lanceolate-ovate to oval in shape and their margins are smooth. The upper surface of the leaflets is medium green and short-pubescent to glabrous, while their lower surface is pale green and glabrous. The terminal leaflet of each trifoliate leaf has a slender petiolule (basal stalklet) up to " long, while the lateral leaflets have slender petiolules less than 1/8" long. The erect to ascending flowering stalk is light green to reddish green and short-pubescent; it is usually leafless, although a less common variety of Naked-Flowered Tick Trefoil has 1-2 trifoliate leaves. The upper part of the flowering stalk consists of a raceme or narrow panicle of flowers up to 1' long. The flowers are arranged along the stalk in widely spaced pseudo-whorls. The pedicels of the flowers and lateral branches (if any) are about -" long.

Individual flowers consist of 5 whitish pink or pale lavender petals, a short tubular calyx with blunt teeth that is greenish red to white, several stamens with white filaments, and a pistil with a single style. The corolla of each flower has a typical pea-like structure consisting of an erect banner, a straight horizontal keel, and a pair of spreading wings. The calyx is short-pubescent and its bottom tooth is larger in size than the others. The blooming period occurs from mid- to late summer for about 1 month. On each plant, only a few flowers are in bloom at the same time and they are not noticeably fragrant. The flowers are replaced by flattened seedpods called 'loments.' The loments usually have 2-3 one-seeded segments (less often, 1 or 4 segments); the upper side of each segment is straight or slightly concave, while the lower side is convex or rhombic. The lateral sides of each loment are covered with short hooked hairs; each loment has a long stipe (about " long) at its base and a shorter beak (less than " long) at its tip. Each segment of the loment is about 8 mm. (1/3") long. The root system consists of a short broad taproot or caudex. This wildflower reproduces by reseeding itself.

The preference is light to medium shade, mesic conditions, and a slightly to moderately acidic soil containing sand, rocky material, or loam with decaying organic matter. The root system of this wildflower fixes nitrogen into the soil via symbiotic bacteria.

Range & Habitat: Naked-Flowered Tick Trefoil is occasional in central and southern Illinois, while in the northern section of the state it is uncommon (see Distribution Map); it is native. Habitats consist of mesic beech-maple woodlands, sandy oak woodlands, and rocky woodlands where sandstone is present. This wildflower occurs in higher quality woodlands where the native ground flora is intact.

Faunal Associations:
The flowers are cross-pollinated by bumblebees, other long-tongued bees, and Halictid bees; these visitors collect pollen. Nectar is not available as a floral reward. Other insects feed on the foliage and other parts of Desmodium spp. (Tick Trefoils). These species include the caterpillars of several skippers, butterflies, and moths; the leaf-mining larvae of the Buprestid beetles Pachyschelus confusus and Pachyschelus laevigatus; the larvae of the seed weevil Apion decoloratum; the thrips Echinothrips americanus and Neohydatothrips desmodianus; and the aphid Microparsus variabilis. There are also several leaf beetles that feed on the foliage of tick trefoils: Anomoea laticlavia, Bassareus lituratus, Cerotoma trifurcata, Colaspis brunnea, Cryptocephalus insertus, Odontata dorsalis, Pachybrachis nigricornis, Pachybrachis othonus, Phyllecthris dorsalis, and Saxinis omogera. Some vertebrate animals also use these plants as a food source. The seeds are eaten by the Wild Turkey and Bobwhite, while the foliage is palatable to deer, rabbits, horses, cattle, and other mammalian herbivores. Because of the height of the flowering stalk (up to 3') and the habitat (woodlands), White-tailed Deer are probably the primary transporters of the seeds of Naked-Flowered Tick Trefoil as the loments (seedpods) can cling to fur.

Photographic Location: A sandy woodland at the Indiana Dunes National Lakeshore in NW Indiana.

Comments: Naked-Flowered Tick Trefoil is usually easy to identify because, unlike other Desmodium spp. (Tick Trefoils), it produces its leaves and flowers on separate stalks (except for an uncommon variety). While other species in this genus produce leaves that are clearly alternate, Naked-Flowered Tick Trefoil produces its leaves in pseudo-whorls. This species also has loments (a type of seedpod) with straight or slightly concave upper sides above their segments. In contrast, most species of tick trefoil have loments with convex upper sides above their segments. Naked-Flowered Tick Trefoil also prefers shady woodlands, while other species of tick trefoil usually prefer partially shaded savannas or sunny prairies.