Trailing Bush Clover (Lespedeza procumbens) of the Bean (Fabaceae) family is an herbaceous, prostrate perennial that has racemes of pea-type flowers. Genus name recognizes Vicente Manuel de Cespedes (an early text misspelled his name as “de Lespedez”), governor of the Spanish province of East Florida from 1784-1790. Specific epithet is a Latin word denoting the plant’s rootless, ground-hugging stems and branches. In the US, it is found in a broad area bounded by a line from eastern Texas and Oklahoma, into southeastern Kansas, thence to southern Vermont, down to the Florida panhandle and back to Texas. In Arkansas, occurrence is statewide except areas of the Mississippi Alluvial Plain. Preferred habits consist of dry to mesic, sandy to rocky soils in partial shade, such as, open woodlands, woodland borders and pine plantations. Plants occur singly or in loose to dense mat-forming groups. It is also known as Downy Trailing Bush-Clover.
Plants have woody taproots and woody, near-surface, wide-spreading, lateral roots. New stems of mature plants grow from buds along basal remnants of previous year’s otherwise-decomposed stems. The half-dozen or more stems of robust plants, some remaining relatively short, extend away from the root-crown in a random, radiating manner. Early in the growth-year, the pale green stems are erect to ascending with pale green leaves. As stems lengthen, some to 4 feet long, they recline to the ground as additional growth intertwines with ground-hugging plants and ground litter. Leaves subtend a branch or peduncle (stalk of inflorescence); several peduncles may grow from the same node.. Spacing of leaves (internode length) is fairly consistent on any particular stem/branch with internode lengths ranging from ½-1 inch. While the non-vining stems and branches are long and flexible, peduncles are straight (¼-2 inches), firm and leafless. Lengths of branches and peduncles, on any particular stem, are variable along stem-length.. Stems, branches, and peduncles have pilose (dense and soft), spreading (erect) pubescence – pubescence reducing with time. Base-width of stems is to 1/16 inch with diameter of the terete stems and branches gradually and uniformly decreasing distally. Late in the growing season, plants look scraggly as they “interact” with weather conditions.
The petiolate (stalked), alternate leaves have a terminal leaflet and 2 lateral leaflets (odd-pinnate compound leaves) – all on petiolules (stalks of leaflets). Petiolules of terminal leaflets are twice as long those of lateral leaflets. Larger leaves, along lower portion of stems, are to 1¼ inches long (including a ⅛-inch petiolule and a ¼-inch petiole) and 1⅜ inches wide (including petiolules). Leaves have a pair of greenish, linear to acicular stipules (to ⅛ inch long – tapering to a fine point) which quickly dry and persist for a while. Leaves gradually decrease in size distally with a sudden decrease after the early erect to ascending portion of stems recline. Within the area of the pea-type flowers, the small stem/branch leaves (to ⅜ inch long) transition to a pair of narrow-triangular bracts (to < ⅛-inch long); both leaves or bracts subtending an inflorescence.
The elliptic to broadly elliptic leaflets are evenly divided by the primary vein (midrib) with the flat blade ascending to either side. Straight, parallel secondary veins (weakly recessed above and well expressed below) are closely and uniformly spaced before branching near leaflet margin. Tertiary veins, in between secondary veins, form elongate rectangles (longitudinal venation). Slightly recurved leaflet margins are smooth and entire (uncut) with rounded apices that may be shallowly notched (emarginate) and the primary vein may extend beyond leaflet margin. Upper and lower leaflet surface, petioles, and petiolules have spreading pilose pubescence (extends from stems/branches). Leaflet surfaces feel soft. With maturity, upper (adaxial) leaflet surface becomes medium to dark green with the lower (abaxial) surface being a paler green.
Most upper nodes of stems and branches of a robust plant bear an inflorescence of pea-type flowers in August through September; depending on weather. The tiny flowers on short (to 1/16 inch), ascending pedicels (stalks) are in racemes (rachis to 1¾ inches long) terminating long, axillary peduncles (also to 1¾ inches long). Up to a dozen flowers may be in a raceme with flowers in alternate lateral pairs and a terminal pair. Lateral pairs are typically well spaced but 2 pairs may be closely spaced, seemingly in a whorl. The straight, sturdy peduncles position the straight racemes the foliage in an inclined to erect position. Flowering sequence of pairs is up-rachis with individual flowers in bloom for about 2 days. Within racemes, each flower is subtended by a pair of narrow triangular bracts so that 4 bracts subtend each flower pair. Drying soils cause some racemes to not develop fully, resulting in spiky, flower-free peduncles.
Flowers have a bilaterally symmetrical, pea-like structure typical of most species in the Bean family; namely, an upright banner, a pair of wing petals and a partially fused (along lower margins) pair of keel petals. Flowers (viewed from front) are about ⅜ inch tall and ¼ inch wide with a length of ⅜ inch. Front of the broadly flared, ovoid banner is a medium pink with dark pink pollinator guides, separated by light pink veins, radiating from the throat (backside is similarly colored). An opposing pair of forward-trending to projecting, solid light-pink oblanceolate (convex on both sides – gibbous) wings have a narrow, basal claw and a lower auricle (ear). The light-pink to whitish envelope-like keel has a slit along its upper margin, a basal claw on each of its fused and auriculate petals and a stiffened up-arching rib – each petal about the same shape as wing petals. (Claws and auricles of wing and keel petals fit together – see Photo 18.) Keel conceals a white pistil (ovary + style + stigma) and 10 white stamens (filaments + anthers) bearing pale-yellow anthers. Of the 10 stamens, lower halves of 9 filaments are fused into a tubular column and tightly encircle the pistil while the 10th stamen is free-standing between the stamen column and banner. Stamens arch upwards in consonance with the rib of the keel. Anthers, producing yellow pollen, are tightly clustered just inside the keel-slit with the white circular stigma (tip of terete style) at the slit for anthesis. Corolla is set in cupped calyx (3/16 inch long). The calyx has pilose pubescence, with 5 narrowly triangular lobes (1/16 inch long) pressed against the corolla; namely, a proximally connate pair centered on the dorsal side, a single lobe centered below the keel and a pair of down-trending lateral lobes. Other than the calyx, flowers are glabrous (lacking hairs).
Fruits, a flattened pod (legume), with an ovate shape, have a thickened center and a rimmed margin. Apex and base are similarly acute. The apex, though, is pointed (mucronate) and, early-on, may bear a remnant of the style. Pods (<3/16 inch long and >1/16 inch wide) are 4-5 times longer than the clasping, early-persistent calyxes. Flat sides of pods are paper-thin with expressed veins in a rather random pattern and covered with scattered appressed hairs. Pale green during development, mature pods are yellowish tan with a single, loosely held seed. The olive-green, ovoid to oblong seeds are smooth and glabrous with smoothly rounded edges. Seeds, about 3/16 inch long and ⅛ inch wide, are released as the indehiscent pods disintegrate.
In addition to flowers that open for pollination (chasmogamous flowers), Trailing Bush Clover has cleistogamous flowers (remain closed and are self-fertile). Chasmogamous flowers usually occur on long peduncles. Cleistogamous flowers (singly or in clusters) are mostly sessile, but clusters may occur at ends of short peduncles. Both flower types result in pods of about the same size and appearance except pods of chasmogamous flowers may retain remnants of the style for a short time. Cleistogamous flowers seem to occur early in the growing season and with poor weather conditions.
As for gardening, with its long trailing growth habit and small flowers, Trailing Bush-Clover is probably best suited for a natural area. This hardy and long-lived perennial with non-woody stems/branches has tiny, colorful flowers that are eye-catching. Suitable as a ground-cover in partial shade and plants “fix” nitrogen in the soil. Along with other species in the family, seeds are a good food source for quail.
Ten additional species (7 native) of the Lespedeza family occur in Arkansas. Of these, only Creeping Bush Clover (L. repens) has similar habitats, growth habit, and flowers/fruits. L. repens can be distinguished from L. procumbens by appressed pubescence along stems/branches versus spreading pubescence in L. procumbens. L. repens tends to be a smaller plant and flowers trend toward being an overall light pink. Hairy Bush Clover (Lespedeza hirta) was previously addressed in this series of articles.
Article and photographs by ANPS member Sid Vogelpohl
