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  Euphorbiaceae : Euphorbia marginata

  R. Neil Reese

  Euphorbia marginata in an annual herb with white milky sap, erect stems, and growing 20–70 cm tall. The stems are unbranched below inflorescence. The simple, sessile leaves are alternate, ovate to elliptical, 3–8 cm long, with entire margins and a pointed tip. They are a medium green in spring. The upper leaves and bracts gradually develop showy white to pinkish edging. There is a whorl of leaves at the base of the terminal umbel-like inflorescence. The unisex flowers are contained in a cup-like involucre (cyathium), 3–4 mm long with 4-5 white lobes, borne singly at the end of the inflorescence branches. Each cyathia has 1 pistilate flower and 35-60 staminate flowers. The fruit is a hairy capsule 4-6 mm long. Snow on the mountain blooms from June to October on prairies, pastures, roadsides and waste places, usually on calcareous soils, throughout South Dakota.

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  Fabaceae: Amphicarpaea bracteata

  R. Neil Reese

  Amphicarpaea bracteate is a herbaceous annual vine with thin green stems reaching up to 2 m in length, found climbing on forbs, grasses and shrubs or sprawling on open hillsides or stream banks in shaded areas. The trifoliate alternate leaves have petioles that are 2-10 cm long with persistent membranous stipules. The leaflets are thin ovate with an acute apex and 2-10 cm long by 1.8-7 cm wide. Mouse beans produce 2 types of flowers. The above-ground flowers are found in axillary racemes (1.5-9cm long) and bloom in late summer. Each flower is subtended by 2 bracts. The calyx is composed of 5 sepals form a tube of 4-5 mm with 4 deltoid lobes extending 0.5-2 mm. The papilionaceous corolla is white to lilac in color. The stamens are diadelphous and there is a single pistil that forms a legume that is 1.4-5 cm long containing 2-5 seeds. The cleistogamous flowers are produced on creeping branches and lack well developed petals. They produce a single-seeded black pods containing 1 white seed about 1 cm in diameter.

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  Fabaceae : Apios americana

  R. Neil Reese

  Apios americana is a perennial herbaceous vine growing from slender rhizomes that produce tubers that get up 6 cm in diameter. The stems grow to 5 m long and climb or sprawl over shrubs and trees. The compound pinnate leaves are inserted in an alternate pattern, having deciduous stipules that are 5-7 mm long. The leaves usually have 5-7 leaflets that are ovate to lance-ovate and rounded at the base, with petioles that are 1.5-8 cm long. Flowers are organized in racemes that have a short peduncle (2-5 cm long) and are found in the axils of leaves. The calices are tubular with the lower lobe triangular and up to halve as long as the tube. The corolla is papilionaceous 10-14 mm long, with the banner reflexed, whitish dorsally and reddish ventrally. The wings are brown to purple, downcurved, and the keel is reddish brown. There are 10 diadelphous stamens, and the legume is straight to slightly curved 5-50 mm by 4-6 mm.

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  Fabaceae: Astragalus agrestis

  R. Neil Reese

  Astragalus agrestis is a perennial, herbaceous plant with a fibrous root system and short, slender rhizomes, forming loose clumps or mats. Mature plants typically reach 15–50 cm in height. Stems are erect to ascending, slender, and sparsely hairy to nearly glabrous. Leaves are alternate, pinnately compound, 5–15 cm long, with 7–15 narrow, linear to lanceolate leaflets, each 1–3 cm long and 2–5 mm wide, with entire margins and acute tips. Leaflet surfaces are green and glabrous or sparsely hairy. Petioles are present, 2–6 cm long. Stipules are present, small, lanceolate, and caducous. Flowering occurs from May to July, with inflorescences forming erect racemes 5–15 cm long, bearing 5–20 pea-like flowers. Flowers are 8–12 mm long, with five free sepals fused at the base, forming a tubular to campanulate (bell-shaped) structure approximately 3–5 mm long. The sepals are lanceolate to ovate, tapering to a pointed tip, and are typically green with fine, soft hairs on the surface, giving a slightly fuzzy texture. There are five petals forming a typical papilionaceous corolla. The banner is 8–12 mm long and about 5–7 mm wide; broadly ovate to broadly elliptic in shape, with a slightly rounded or notched apex, often displaying a pale purple to pinkish hue. The wings are 7–10 mm long and 3–5 mm wide; narrowly oblong to lanceolate, enclosing the keel and slightly shorter than the banner. The keel is 6–9 mm long and 2.5–4 mm wide; narrowly lanceolate and curved, enclosing the reproductive organs. Petal coloration varies from pale purple to pinkish or white. Stamens are ten, nine fused and one free (diadelphous), with yellow anthers. The pistil has a single ovary with a slender style and a capitate stigma. The fruit is a legume pod, 2–4 cm long and about 3–5 mm wide, slender and slightly curved or straight. It is covered with fine, short hairs (pubescent), and typically dehisces (splits open) along both sutures when mature to release seeds. Pods mature from July to August. Field milkvetch is native to South Dakota and occurs in dry to mesic prairies, open woodlands, and rocky slopes, favoring well-drained, sandy or gravelly soils under full sun to partial shade, throughout the state.

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  Fabaceae: Astragalus canadensis

  R Neil Reese

  Astragalus canadensis is a rhizomatous perennial herb with erect stems growing 30-120 cm in height. The herbage is sparsely to densely covered in ax-shaped hairs. The alternate, sessile to short petiolate, compound odd-pinnate leaves are 5-35 cm long, with 11 to 35, narrow, elliptic leaflets, 1–4 cm long, with blunt to rounded tips and lanceolate stipules 5–10 mm long. The inflorescence consists of axillary spike-like racemes, 4-20 cm long, with 30 to 100 papilionaceous flowers on a peduncle of 2-10 cm. The calyx tube is 4-7 mm long, with teeth 1-4 mm long. The corolla is greenish white to yellowish white, the banner 11-16 mm long, the wings are 10-14 mm long and the keel is 9-13 mm long and occasionally purple tipped. The wings and keel are narrowed at the base. The fruit are erect legumes, elliptic to cylindric in shape, and 9–15 mm long. Canada milkvetch blooms from May through August in moist prairies, along riverbanks and on open wooded hillsides in much of South Dakota.

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  Fabaceae : Astragalus ceramicus var. filifolius

  R. Neil Reese

  Astragalus ceramicus var. filifolius is a perennial herb from buried, spreading rhizomatous caudex. The solitary stems are lax to ascending, 3-40 cm long with silvery, stiff, appressed hairs. The compound leaves are alternate, odd pinnate, 2–17 cm long, often reduced to just the rachis, with the lower most leaves having 3-5 leaflets, with slender petioles and lanceolate stipules, 2–6 mm long, and often united basally. The inflorescence is comprised of axillary racemes of 2-7 white to light purple, papilionaceous flowers on peduncles of 1.5-7 cm in length. The hairy calyx tube is 2-3 mm long with teeth ~1 mm long. The banner is 6-9 mm long, the wings 6-8 mm long and the keel 6-8 mm long, all of the petals narrowed near the base. The fruit are legumes, each pod has a stipe of 1-3 mm in length, is inflated, red mottled, 3-5 cm long and 1.4-2.6 cm in diameter. Painted milkvetch blooms in June and July in sand dunes and sandy prairies in south central and northwest South Dakota.

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  Fabaceae: Astragalus cicer

  R. Neil Reese

  Astragalus cicer is a perennial, herbaceous plant with a deep, fibrous root system and rhizomatous growth, forming dense clumps or mats. Mature plants typically reach 50–100 cm in height. Stems are erect, stout, branched, and sparsely hairy to glabrous. Leaves are alternate, pinnately compound, 10–25 cm long, with 15–25 oblong to lanceolate leaflets, each 1.5–3 cm long and 5–10 mm wide, with entire margins and rounded to acute tips. Petioles are 5–15 cm long. Stipules are present, ovate-lanceolate, and caducous. Flowering occurs from June to August, with inflorescences forming dense, erect racemes 10–20 cm long, bearing 20–40 papilionaceous flowers. Flowers are 12–18 mm long, with a calyx forming a tubular to campanulate tube 5–7 mm long, composed of five fused sepals with lanceolate lobes 3–5 mm long, densely covered with fine hairs. The corolla has a prominent banner (standard petal) 12–15 mm long and 8–10 mm wide, broadly ovate with a rounded apex; wings are 10–13 mm long and 4–6 mm wide, narrowly oblong; and the keel is 9–12 mm long and about 3–4 mm wide, narrowly lanceolate and curved, enclosing the reproductive organs. There are ten stamens, diadelphous (nine fused and one free), with yellow anthers. The pistil has a single ovary with a slender style and capitate stigma. The fruit is a legume pod, 6–14 mm long, bladder-like, inflated, and roughly spherical. These are initially green and thinly fleshy, maturing to a stiff, papery, dark brown or black color, and are covered in short, stiff hairs. Each pod typically contains multiple seeds and features a persistent, curved style, dehiscing along two sutures at maturity. Pods mature from August to September. Cicer milkvetch is native to eastern Europe and western Asia, introduced in South Dakota and commonly found in pastures, roadsides, and disturbed sites, thriving in well-drained, fertile soils under full sun.

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  Fabaceae : Astragalus crassicarpus

  R. Neil Reese

  Astragalus crassicarpus is a perennial, prostrate to suberect herb, 11-60 cm in height, with many hair covered stems growing from a well branched caudex atop of a tap root. The alternate, compound leaves are pinnately dissected, 4-13 cm long, with 13-27 oblanceolate to linear leaflets, 3-17 mm long, 3-6 mm wide, with hairs that make them appear slightly grayish, with lanceolate stipules 3-8 mm long. The inflorescence is composed of axillary racemes of 5-25 bluish, purple or white with purple-tipped papilionaceous flowers on peduncles 2-10 cm long. The calyx tube is 6-9 mm long, with black and/or white stiff appressed hairs and teeth 1-4 mm long. The banner petal is notched, 16-24 mm long, the wings are 16-18 mm long, and the keel is 11-15 mm long and narrowed at the base. The fruit is a red to purple, globose, fleshy legume, 15 -25 mm long, resembling a plum. Ground plum blooms from April to June on prairie hillsides, along stream bank and in open woods throughout South Dakota.

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  Fabaceae : Astragalus gilviflorus

  R. Neil Reese

  Astragalus gilviflorus is a perennial, cushion-forming, acaulescent or very short-stemmed (< 3 cm long) herb, covered with silvery ax-shaped hairs. The compound, alternate, petiolate, leaves, have conspicuous, membranous or chartaceous stipules that are persistent, clasping and forming a tube or sheath around the stem. The leaves are trifoliolate, sometimes odd pinnate with 5 leaflets, the leaflets oblanceolate, 5–20 mm long with entire margins. The inflorescences are axillary, globose capitate or subcapitate racemes with 1-6 flowers. The 5-lobed cylindrical calyx tube is hairy, 6-15 mm long with teeth 1.5-4 mm in length. The corolla is papilionaceous, the white petals are clawed (narrowed at the base), the banner is slightly reflexed, 15–30 mm long, the wings 12-24 mm long and the keel is 10–22 mm long, often purple-tipped. The fruit is a legume, 6-10 mm long, oblong or ellipsoidal, exserted from calyx, beaked, hairy, and contains 3-10 mitt shaped seeds. Prairie milkvetch blooms in May and June on rocky prairie hilltops, slopes or barren flats in western South Dakota.

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  Fabaceae: Astragalus racemosus

  R Neil Reese

  Astragalus racemosus is a perennial herb growing from a branched caudex, with multiple, often branched, erect to ascending stems, 15-70 cm tall that are thinly to densely covered with appressed hairs. The alternate, compound odd-pinnate leaves are4-15 cm long, with short petioles below and sessile above, with stipules 3-12 mm long. there are 11-31 leaflets, 1-4 cm long, the lower leaves having broader lance-elliptic leaflets, and the upper leaves with narrower lanceolate leaflets. The inflorescence consist of axillary racemes with 15-70 papilionaceous flowers on peduncles 3-11 cm long. The flowers are generally nodding on pedicels 2-3.5 mm long. The calyx tube is covered in white, appressed hairs, .bell-shaped, 5-7 mm long, sometimes swollen at the base with 5 awn-like lobes, 2-10 mm long. the 5 petals are white to cream colored with purplish tips and or streaks. The banner is 6-12 mm long, the clawed (constricted at the base) wings 12-19 mm long, and the clawed keel 10-16 mm long. The fruit are triangularly compressed legumes, 3.5-7 cm long, 3-6 mm in diameter, with a stipe on the end that is up to 7 mm long. Alkali milkvetch blooms from May to July on poorer soils in prairies, plains, hillsides and in stream valleys in western South Dakota.

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  Fabaceae : Dalea aurea

  R. Neil Reese

  Dalea aurea is a perennial herb with 1 to several erect stems coming from a woody caudex atop a taproot and growing 20-75 cm in height. The stems are simple or branched above and covered with silky hairs. The petiolate leaves are alternate, compound odd-pinnate, blades 1-4 cm long, with 5-7 oblanceolate leaflets, 4-16 mm long. The leaves are largest toward the stem base and are reduced above. The inflorescence consists of silky-haired, many flowered, terminal cone-like spikes on the main stem and branches, becoming oblong-cylindrical, 1.5-7 cm long. The calyx tube is 2-3 mm long, with teeth 3.5-5 mm long and is densely covered with silky hairs. The corolla is papilionaceous, yellow, with all of the petals clawed (narrowed at the base). The petals above the claws measure as follows: banner 6.5-8.6 mm, wings 5-6 mm, and the keel 5.7-8.5 mm long. The fruit is a one-seeded legume, 3-4 mm long and covered with silky hairs. Golden prairie clover blooms from June into September in prairies, open hillsides, in ravines and in stream valleys in western and southwestern South Dakota.

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  Fabaceae : Dalea candida

  R. Neil Reese

  Dalea candida is a perennial herb with 1-several erect stems, simple or branching from above, growing from a caudex attached to a thick taproot, each stem 30 to 100 cm in height. The alternate, compound odd-pinnate, leaves are 1.5-6 cm long, with a short petiole, and 5-13 narrow, gland-dotted, light green leaflets, each 5-35 mm long. The inflorescence is a loose to dense cylindrical spike of flowers, 1.5-7.5 cm long, at the tip of each stem or stem branch. Each flower has a green calyx tube 1.9-2.7 mm long with teeth 0.6-1.8 mm long. The papilionaceous corollas have white clawed (narrowed at the base) petals that measure above the claws: banner 4-5.7 mm long, the wings and keel 3.2-5.3 mm long. The flowers at the base open first and the upper ones bloom later. The fruit is a green oval legume pod, 2.5-4.5 mm long, containing one seed. White prairie clover blooms from May to August on prairies, open woodlands and roadsides throughout South Dakota.

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  Fabaceae : Dalea enneandra

  R. Neil Reese

  Dalea enneandra is a perennial herb with 1-3 erect stems, branched above the middle, which are 5-10 dm tall and arise from a caudex attached to a yellow taproot. The alternate, nearly sessile, pinnately compound leaves are 1.3-2.6 cm long, with leaves on the main stem often deciduous by time of anthesis. The leaves 5-13 leaflets, narrowly oblanceolate, 4-12 mm long with black glands on the leaflets and midrib. The inflorescence consists of terminal, 2-ranked spikes, with 5-35 flowers, subtended by bracts, 3-4 mm long with pale or white membranous margins. The calyx tube is covered with silky hairs, 3-3.7 mm long with 5 teeth 3.3-4.6 mm long. The papilionaceous white petals are clawed (narrowed at the base) with the remainder of the petals measuring as follows: banner 5.7-7 mm, wings 2.8-4.1 mm, and the keel 5.5-7 mm long. There are 9 stamens. The fruit are one-seeded legumes, 3-4 mm long. Nine-anther prairie clover blooms in July and August in prairies, on hillside and in stream valleys in most of South Dakota.

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  Fabaceae : Dalea purpurea

  R. Neil Reese

  Dalea purpurea is a perennial herb, with ascending to prostrate stems, which grow singly or in groups from a woody caudex, 20 to 90 cm in height. The stems can vary from smooth to very hairy. The alternate, odd-pinnate compound leaves are 1.5-4.5 cm long, with 3-7 linear to linear-oblanceolate leaflets, 10-28 mm long and can be smooth to hairy. The inflorescence consists of terminal, conical, densely hairy spikes, 1-7 cm long attached to a peduncles 0-15 cm long. Each flower is subtended by hairy bracts, 2.5-5.8 mm long. The densely hairy, bell-shaped calyx tube is 2-3 mm long with teeth 1-2 mm long. The papilionaceous corolla has clawed (narrowed at the base), pinkish to rose to purple-colored petals with the petal length beyond the claws as follows: banner 4.5-7 mm, wing and keel 3-5 mm long. The fruit is a single-seeded legume, 2-2.5 mm long. Purple prairie clover blooms from May into August on prairies, hillsides, open woods and stream valleys throughout South Dakota.

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  Fabaceae : Glycyrrhiza lepidota

  R. Neil Reese

  Glycyrrhiza lepidota is a perennial herb arising from deep, woody, aromatic roots with multiple, erect stems, which grow 30-120 cm in height and are typically dotted with glands. The leaves are alternate, with petioles 5-50 mm long and stipules 3-7 mm long. The blades are compound odd-pinnate with oblong to lanceolate leaflets, 2-7 cm long with glandular dots, in groups of 7 to 21. The inflorescences are axial, dense, spike-like racemes of numerous flowers, with peduncles 1–6 cm long. The flowers have tubular-campanulate green calyx tubes that are 2-2.5 mm long, with teeth 2.5–3 mm long, the tube and teeth both having stalked glands. The papilionaceous corollas have white to yellowish white petals, the banner moderately erect, 10-14 mm long, keel and wings 8-12 mm long. There are 9 united stamens and 1 separate stamen. The fruit is an ellipsoid legume, 1–2 cm long going from green to orangish-brown with age and covered with hooked bristles 2–3 mm long. The fruit remain through the winter. American licorice blooms from July into September in prairie ravines, along streams and lakeshores and in other moist areas throughout South Dakota.

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  Fabaceae: Hylodesmum glutinosum

  R. Neil Reese

  Hylodesmum glutinosum is a perennial, herbaceous vine or sprawling plant in the Fabaceae family. It grows from a deep taproot and produces slender, sometimes hairy, trailing or climbing stems typically growing from 30 to 90 (140) cm tall. Leaves are alternate, trifoliate, with each leaflet ovate to elliptical, 3–7 cm long and 1.5–3 cm wide, with entire to slightly toothed margins. Each trifoliate leaf is attached to the stem by a petiole, with small, leaf-like stipules at the base of each leaf petiole. Leaflets are attached to the petiole by short stalks called petiolules. Flowering occurs mid to late summer (June–September). Flowers are pea-shaped, 1–1.5 cm long, purplish pink to lavender, appearing singly or in small clusters in leaf axils. The calyx has five sepals fused into a tubular base with five pointed lobes, 5 to 8 mm long and often glandular-hairy. The corolla consists of five petals typical of legumes: one large upright banner, two lateral wings, and two fused keel petals, ranging from 12 to 20 mm long. There are 10 stamens arranged in a diadelphous configuration; nine stamens are fused together into a tube surrounding the pistil, while one stamen remains free. The pistil is superior with a single carpel; the slender style curves upward to a small stigma. Fruits are legume pods measuring 3 to 6 cm long, slightly sticky or glandular, containing several seeds, and mature in summer to early fall. In South Dakota, large tick-trefoil is typically found in eastern and southeastern regions where habitats include open woodlands, prairies, thickets, streambanks, and sometimes along roadsides or disturbed areas.

  Synonym: Desmodium glutinosum

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  Fabaceae: Lotus corniculatus

  R. Neil Reese

  Lotus corniculatus is a perennial herbaceous legume that spreads by stolons and forms low mats or small clumps. Stems are slender, trailing or ascending, typically 10–50 cm long, and often glabrous or sparsely hairy. Leaves are alternate and compound, typically trifoliate with three leaflets measuring about 1 to 3 cm long and 0.5 to 1.5 cm wide; leaflets are obovate to elliptic with entire margins and smooth surfaces, sessile or have very short petiolules, about 5–20 mm long and 3–10 mm wide, with small stipules at the base of the leaf stalks. Flowering takes place from late spring through early fall (May–September). The inflorescence is an umbel-like cluster of 3 to 10 flowers. Flowers are bright yellow, sometimes with orange-red tinges on the petals, about 1 to 1.5 cm long, with a typical papilionaceous structure: a broad, rounded standard petal, two lateral wing petals, and a keel formed by two fused petals. Each flower is subtended by a calyx of five sepals fused at the base into a tubular cup about 5 to 8 mm long, with five pointed lobes that are lanceolate to ovate in shape and covered with fine hairs. Flowers have ten stamens, nine of which are fused, and a superior ovary. The fruit is a slender, curved pod about 2 to 4 cm long containing several seeds Bird’s-foot trefoil is native to Eurasia but widely naturalized and invasive in South Dakota, often found in pastures, roadsides, pastures, grasslands, and disturbed sites statewide.

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  Fabaceae: Lupinus argenteus

  R. Neil Reese

  Lupinus argenteus is a perennial herbaceous plant growing 30 to 90 cm tall. It has a fibrous root system with occasional short rhizomes but no stolons. The stems are erect, often covered with silvery, silky hairs giving the plant a grayish appearance. Leaves are alternate and palmately compound, typically with 7 to 11 narrow leaflets measuring about 2 to 5 cm long and 0.5 to 1 cm wide; leaflets are linear to lanceolate with entire margins and covered in fine silvery hairs. Leaf petioles are 5 to 15 cm long. The inflorescence is a dense raceme of pea-shaped flowers blooming from late spring to mid-summer (June–August). Each flower is subtended by a calyx of five sepals fused into a tubular structure about 6 to 10 mm long, with five pointed lobes that are ovate to lanceolate and densely covered with silvery hairs, each lobe measuring approximately 3 to 5 mm long and 1.5 to 3 mm wide. Flowers are typically blue to purple, about 10 to 15 mm long, with the classic papilionaceous form: the standard petal is broadly ovate and 8 to 12 mm long and 6 to 9 mm wide; the two wing petals are about 7 to 10 mm long and 3 to 5 mm wide; and the keel formed by two fused petals is about 7 to 11 mm long and 3 to 4 mm wide. Flowers have ten stamens, nine of which are fused, and a superior ovary. The fruit is a pod approximately 3 to 6 cm long containing several seeds. In South Dakota, Silvery lupine is native and found in dry open woods, meadows, and rocky slopes primarily in the western and Black Hills regions.

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  Fabaceae: Medicago lupulina

  R. Neil Reese

  Medicago lupulina is an annual or short-lived perennial herbaceous plant growing 10 to 50 cm tall. It has a fibrous root system with occasional short stolons allowing it to spread across the ground. The stems are slender, often sprawling or ascending, and glabrous to sparsely hairy. Leaves are alternate and trifoliate, with three oval to obovate leaflets measuring about 0.8 to 2.5 cm long and 0.5 to 1.5 cm wide; leaflets have entire or slightly serrated margins and smooth surfaces. Leaflets are sessile or have very short petiolules, and stipules are small and lanceolate at the base of the leaf stalks. The inflorescence is a small, dense raceme or head of 5 to 20 bright yellow, pea-shaped flowers blooming from late spring through summer (May–August). Each flower is subtended by a calyx of five sepals fused at the base into a tubular cup about 3 to 5 mm long, with five pointed lobes that are lanceolate and often hairy. Flowers are about 5 to 8 mm long. The corolla’s standard petal is broadly ovate, measuring approximately 5 to 7 mm long and 4 to 6 mm wide; the wing petals are about 4 to 6 mm long and 2 to 3 mm wide; and the keel, formed by two fused petals, is about 4 to 7 mm long and 1.5 to 3 mm wide. Flowers have ten stamens, nine of which are fused, and a superior ovary. Fruits are coiled, single-seeded pods resembling tiny spirals, maturing in late summer. Black medick is native to Eurasia but naturalized widely in North America, including South Dakota, often found in lawns, pastures, roadsides, and disturbed sites statewide.

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  Fabaceae: Medicago sativa

  R. Neil Reese

  Medicago sativa is a perennial herbaceous plant growing 30 to 100 cm tall, often forming dense stands. It has a deep, extensive taproot system that allows it to access deep soil moisture. The stems are erect to ascending, slender, and typically glabrous or sparsely hairy. Leaves are alternate and trifoliate, with three oval to oblong leaflets measuring about 1.5 to 4 cm long and 0.8 to 2 cm wide; leaflets have smooth or slightly serrated margins and a fine, soft pubescence on the surface. Leaflets are petiolulate with short stalks about 2 to 5 mm long, and stipules are small and lanceolate at the base of the leaf stalks. The inflorescence is a raceme or spike-like cluster of 10 to 40 pea-shaped flowers blooming from late spring through summer (May–August). Each flower is subtended by a calyx of five sepals fused at the base into a tubular cup about 5 to 8 mm long, with five pointed lobes that are lanceolate to ovate and often covered with fine hairs. Flowers are about 10 to 15 mm long. The corolla’s standard petal is broadly ovate and measures approximately 9 to 14 mm long and 7 to 10 mm wide; the wing petals are about 8 to 12 mm long and 3 to 5 mm wide; the keel, formed by two fused petals, is about 8 to 13 mm long and 3 to 5 mm wide. Flowers are typically purple to violet, sometimes pink or white. Flowers have ten stamens, nine of which are fused, and a superior ovary. The fruit is a spiral coiled pod about 2 to 4 cm long containing several seeds, maturing from late summer to early fall. Alfalfa is native to southwestern Asia but widely cultivated and naturalized in North America, including South Dakota. Primarily used as a forage crop, it is occasionally found naturalized along roadsides and disturbed sites.

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  Fabaceae: Melilotus officinalis

  R. Neil Reese

  Melilotus officinalis is a biennial or short-lived perennial herbaceous plant growing 30 to 150 cm tall. It has a deep taproot and a fibrous root system capable of fixing nitrogen. The stems are erect, slender, and often branched, with a smooth to sparsely hairy surface. Leaves are alternate and trifoliate, with three oval to obovate leaflets measuring about 1.5 to 4 cm long and 1 to 2 cm wide; leaflets have finely serrated margins and a smooth to slightly hairy surface. The leaflets are petiolulate with short stalks about 2 to 5 mm long, and stipules are small and lanceolate at the base of the leaf stalks. The inflorescence is a long, slender raceme of small, fragrant, bright yellow pea-shaped flowers blooming from late spring to early fall (May–September). Each flower is subtended by a calyx of five sepals fused at the base into a tubular cup about 3 to 6 mm long, with five pointed lobes that are lanceolate and often hairy. Flowers measure about 6 to 9 mm long. The corolla’s standard petal is broadly ovate, approximately 6 to 8 mm long and 4 to 6 mm wide; the wing petals are about 5 to 7 mm long and 2 to 3 mm wide; the keel, formed by two fused petals, is about 5 to 8 mm long and 2 to 3 mm wide. Flowers have ten stamens, nine of which are fused, and a superior ovary. The fruit is a small pod about 4 to 8 mm long containing one to two seeds. Yellow sweet clover is native to Eurasia but widely naturalized and sometimes invasive in North America, including South Dakota, commonly found in roadsides, fields, and disturbed habitats statewide.

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  Fabaceae: Mimosa nuttallii

  R. Neil Reese

  Mimosa nuttallii is a sprawling perennial herb with stems that grow up to 1 m long, covered with small prickles, 0.5-2 mm long. The alternate leaves are bipinnate leaf blades are divided into four to nine pairs (pinnae), and each of these have 8–15 pairs of leaflets, 3-9 mm long with a prominent midrib visible on the upper pairs and stipules 4-6 mm long. The leaves exhibit nyctinastic movement, folding up quickly when touched. The inflorescence consists of axillary, many-flowered heads, with peduncles 3-9 cm long. The pink to lavender flowers are sessile, with a minute calyx. The 5 united petals form a narrow tube about 4 mm long and lobes of about 1 mm, with 8-12 stamens inside. The fruit is a legume, 3-12 cm long and covered with prickles and explodes upon drying expelling the seeds. Nuttall’s sensitive briar blooms from April into September on prairies, in ravines and in open woodlands in central South Dakota.

  Synonym: Schrankia nutallii

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  Fabaceae : Oxytropis lambertii

  R. Neil Reese

  Oxytropis lambertii is an acaulescent perennial herb growing from a branching caudex, forming clumps of leaves that appear silvery due to a covering of short stiff and ax-shaped hairs. The leaves are up to 15 cm long with 7 to 19 linear-lanceolate leaflets, 5-40 mm long and 1-6 mm wide, with membranous, hairy stipules 7–24 mm long and having sharply pointed tips. Inflorescences develop on multiple, silvery-haired flowering stems (scapes), 10–30 cm long including the peduncle, each with 6 to 25 flowers per raceme. The calyx has a dense white covering of hairs, the sepals forming a tube that is 6-7 mm long with teeth 1.5-3 mm long. The papilionaceous flowers have red to blue to purple petals, the banner 15–25 mm long, the wings 12-20 mm long and the keel 13-19 mm long. The fruit is an silvery-haired, erect, sessile leathery or woody legume, 1–2 cm long, including the long beak. Purple locoweed blooms from May into August on prairies, plains, river bluffs and hillsides in much of South Dakota.

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  Fabaceae : Oxytropis sericea

  R. Neil Reese

  Oxytropis sericea is an acaulescent perennial herb growing from a much-branched caudex, forming mounds of silky-haired leaves. The leaves are 4-30 cm long with 11 to 25 lanceolate to narrowly ovate leaflets, 5–40 mm long and 2-10 mm wide. The petioles are 1-15 cm long with membranous, hairy stipules, 8–22 mm long. Inflorescences are terminal racemes of 6 to 30 flowers atop of erect to ascending scapes (flowering stems), 5–30 cm long, including the peduncle. The calyx is covered in white and/or black hairs, and forms a tubular-campanulate tube, 8-12 mm long with unequal teeth 2-5 mm long. The papilionaceous corolla is white to yellowish white; the banner 16–25 mm long and deeply lobed, the wings 15-20 mm long, and the keel is 12-17 mm long with a small appendage at the distal end. The fruit are sessile, erect, oblong legumes, 15–25 mm long, with a short beak and having a few short stiff hairs to a silky covering of hair. White locoweed blooms from April into June in rocky prairies, hillsides, open woods and valleys in southwestern South Dakota.

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  Fabaceae : Pediomelum argophyllum

  R. Neil Reese

  Pediomelum argophyllum is a perennial herb with multiple, erect to ascending, widely branching stems, 20-80 cm in height, growing from a subterranean caudex that forms colonies. The stems are usually covered in silvery hairs. The alternate leaves are palmately compound with 3 to 5 leaflets with 1-5 cm long petioles. The leaflets are 1–4 cm long, with entire margins, and covered with dense, shiny hairs. The inflorescence consists of axillary spikes, 2–9 cm long including the peduncle, with 1 to 5 leafy bracts and 2-5 well separated whorls of 3-6 flowers each. The densely hairy calyx forma a campanulate tube with 2 lips, 2–3 mm long with 4 upper teeth, 2.5-3 mm long and a lower tooth 7-10 mm in length. The purple, papilionaceous corolla has a banner 5-7 mm long with a short spur, the wings are 4-6 mm long and the keel 4-5 mm long. The fruit is a hairy, 1-seeded legume, 7-9 mm long with a short beak, and mostly enclosed by the calyx. Silverleaf scurf-pea blooms from July into September on prairies, hillsides, open woodlands, sand dunes and in stream valleys throughout South Dakota.

  Synonym: Psoralea argophylla,