Strophostyles umbellata (Muhl.) Britt. - Climbing twisted-pea

Strophostyles umbellata plant

Family - Fabaceae

Stems - Vining, twining, herbaceous, retrorse pubescent, terete to slightly angled, often twisted, often purplish in strong sunlight.

Leaves - Alternate, trifoliolate, stipulate, stipellate, petiolate. Stipules spreading, triangular, 2-3mm long, striate-nerved, glabrous to strigose, entire. Petioles to +2cm long, sparse antrorse strigose, with a deep adaxial groove. Stiples on all leaflets ovate-triangular, entire, 1.2mm long, mostly glabrous. Petiolules of lateral leaflets 1-2mm long, pubescent adaxially. Petiolule of terminal leaflet 6-7mm long, pubescent as the petiole. Leaflets ovate to lance-ovate, 3-6cm long, .8-1.5cm broad, entire, subacute to rounded at the apex, sparse antrorse strigose on both surfaces, deep green above, light green abaxially. Margins antrorse strigose. Lateral leaflets typically oblique at the base.

Inflorescence - Flowers 3-4 at the end of the peduncles and forming a false whorl. Peduncle axillary, angled, minutely winged, with very sparse retrorse strigose pubescence, to +/-9cm long. Pedicels .5-2mm long, retrorse pubescent. Bracts subtending the calyx ovate to ovate-lanceolate, 1mm long, .6mm broad, shorter than the calyx tube, rounded to subacute at the apex, glabrous adaxially, strigose abaxially.

Strophostyles umbellata inflorescence

Flowers - Corolla papilionaceous, pink. Standard pink, 1.5-1.9cm broad, 1.2cm tall, emarginate at the apex or not, glabrous. Wings pink at the apex, rounded with a short claw (to 2mm long), glabrous, 1cm long, 5mm broad, free from keels. Keels white but wine-purple at the apex, strongly deflexed and surrounding the fertile floral organs, glabrous externally, connate on lower margin. Stamens diadelphous, the tube white and glabrous, deflexed and connate around the style. Free portions of stamens 5-6mm long. Anthers yellow, .7mm long. Ovary green, superior, 5-6mm long in flower, sericeous. Calyx bilabiate, green, sparse pubescent. Calyx tube to 3mm long, glabrous internally. Lower lip 3-lobed. Central lobe acuminate-triangular, 1-2mm long, with some strigose hairs near the apex. Lateral lobes acute. Upper lip with one lobe. Lobe rounded. All calyx lobes ciliolate-margined (use lens to see). Fruit antrorse strigose, slightly compressed, to 6cm long, many-seeded.

Strophostyles umbellata flowerFlower close-up.

Strophostyles umbellata fruitDeveloping fruit.

Flowering - July - October.

Habitat - Low or upland woods, thickets, bluffs, along streams, wooded slopes, ridges.

Origin - Native to U.S.

Other info. - This species can be found mostly in the southern half of Missouri but it is also present in counties along the Mississippi and Missouri rivers. There are three species of Strophostyles in Missouri and the genus is easy to recognize because of the deflexed and curled keel petals of the corolla. Differentiating between the three species can be difficult at times and the differences in the bracts at the base of the calyx tube seem to be the best way distinguish between these species.

Photographs taken at Fort Benning, GA., 10-10-05.


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