Amberique Bean (Trailing Wild Bean) is a native twining annual vine, reaching 3 to 8 feet in length, that by maturity may have a reddish-purple coloration on the stems and leaf stalks.
branch, are circular in cross section or may be slightly angled.
Leaves are alternate, stalked, mostly smooth and three-parted – up to three inches long. The underside of the leaflets is much paler in color with whitish hair on the ribs. Leaflets are ovate in shape. The two lateral leaflets are on short stalks and have unequal lobes toward the base; the terminal leaflet usually has equal lobes and has a longer stalk. There are small stipules at the base of the petiole.
The inflorescence is a single flower or a long stalked loose cluster (a raceme) of 3 to 10 flowers that are each stalkless, with only 1 or 2 open at one time. Clusters rise from the leaf axils.
Flowers: By mid July there are pink to lilac 5 part pea-type flowers. The calyx is green initially, has 5 unequal pointed teeth with fine hair. The upper pair of lobes are usually united. A pair of small green hairy bracts subtend the calyx and are about the same length as the calyx. The corolla has an upper petal (called a standard or banner) that is rounded, about 1/2 inch wide with a slight notch resembling a fold at the top. There are two lateral petals that are slender and project forward partially enclosing two petals that form the keel, which is curved forward and upward toward the inside of the standard. The keel holds the reproductive parts which consist of 10 stamens united at their bases into two groups and a long style the extends out from an extension of the keel and into the underside of the banner petal – an interesting arrangement.
The fruit matures to a rounded pod up to 3 1/2 inches long that contains 4 to 8 woolly seeds. Pods are green during development and brown to brownish-black when mature. The tip of a pod retains the persistent bent style.
Habitat: Amberique Bean (Trailing Wild Bean) prefers dry sandy soil with sun. Being a legume it is nitrogen fixing.
Names: The genus Strophostyles, is derived from two Greek words – strophos, meaning ‘twisted’ or ‘a band’ and stylos meaning ‘style’ and together referring the twisted or ‘curved’ style of the flower of this genus. The species name, helvola, means ‘pale brownish yellow’ which may refer to the color of the extension of the keel petals, but that is unclear. The author names for the plant Classification are, first, ‘(L.)’ refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. His work was updated by ‘Elliot’ which refers to Stephen Elliot (1771-1830) American botanist and collector whose herbarium was the largest in America at the time. He is noted for A Sketch of the Botany of South Carolina and Georgia.
Comparisons: Only one other bean is similar and present in our area – see note at bottom of the page.
