Rhynchosia spp.

Snoutbeans

Fabaceae

Pantropical and warm temperate regions worldwide

Attracts Pollinators Attracts Butterflies Drought Tolerant

Native to North America

SunFull Sun – Part Shade

WaterLow · drought-tolerant

HardinessZones 8–11

Overview

Rhynchosia spp. is a large genus of roughly 200 species of perennial herbs, twining vines, and low subshrubs in the pea family, Fabaceae. It is pantropical and extends into warm temperate regions, with species across the Americas, Africa, Asia, and Australia. Most plants have the three-parted (trifoliate) leaves typical of the bean family, often dotted with tiny resin glands, and they twine, trail, or stand as small bushy subshrubs depending on the species. The pea-like flowers are usually yellow, sometimes marked with thin reddish or purple lines, and are borne singly or in short racemes from the leaf axils. Short, flattened pods follow, each commonly holding two seeds; in several species these seeds are bicolored bright red and black and have been used as beads. As legumes, Rhynchosia spp. species fix nitrogen through root-nodule bacteria and often grow on poor soils. Most are plants of grassland, scrub, open woodland, and disturbed ground in warm climates, and many are frost-tender. Some twining species can scramble widely and need support or room, and a few are weedy where conditions suit them. The bicolored seeds of some species are reported to be toxic if eaten.

Native Range

Rhynchosia spp. has a pantropical distribution, native across the warmer parts of the Americas, sub-Saharan Africa, southern and eastern Asia, and Australia, reaching into warm temperate zones such as the southern United States. Species grow in grassland, thickets, open woodland, coastal scrub, and disturbed roadsides.

Suggested Uses

Rhynchosia spp. is grown in native, wildlife, and naturalistic plantings, on banks and slopes for cover, and as a nitrogen-fixing component of warm-climate grassland mixes. Twining species are trained over fences and trellises, and the flowers draw bees and other pollinators. Some species are grown mainly for their red-and-black ornamental seeds.

How to Identify

Look for legumes with three-parted leaves often gland-dotted beneath, twining or trailing stems or low bushy growth, and small yellow pea flowers from the leaf axils. The short, flat two-seeded pods are a useful field mark, and in several species the seeds are vividly red and black. The trifoliate leaves and pea flowers separate Rhynchosia spp. from many look-alike vines, though it resembles related bean genera.

Appearance

Size & Dimensions

Height1' - 10'

Width/Spread1' - 6'

Colors

Flower Colors

yellow

Foliage Colors

green

Bloom Information

Bloom Period

~8 weeks

Summer Fall

Most Rhynchosia spp. species flower through the warm season, generally summer into autumn, with timing tied to rainfall in seasonally dry climates. The small yellow flowers open over many weeks as the stems lengthen. Pods ripen and dry in the weeks after flowering.

Detailed Descriptions

Flower Description

yellow, sometimes with reddish lines

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 5-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

sand loam rocky

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

tender

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Grow Rhynchosia spp. in full sun in light, well-drained soil, including poor and sandy ground, since as a legume it needs little added nitrogen. Most species take heat and drought once established but are frost-tender and behave as perennials only in warm, nearly frost-free climates. In cooler regions the frost-sensitive species are grown as warm-season annuals from seed. Twining species are given a trellis, fence, or open ground to scramble over, while subshrubby species stand without support. Water moderately during growth and sparingly once established, as wet, heavy soils cause root rot. Few pests trouble the genus beyond occasional bean-feeding insects.

Pruning

Rhynchosia spp. needs little pruning. Twining species are cut back in late winter or early spring to control their spread and remove dead growth, and frost-killed top growth is cleared in spring where plants are root-hardy. Trimming after flowering limits self-seeding in species that spread readily.