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Medicago polymorpha

bur clover

Fabaceae

Mediterranean Basin and southern Europe

Attracts Pollinators

SunFull Sun

WaterLow

Overview

Medicago polymorpha is a low-growing annual legume reaching 4-24 inches (10-60 cm) long, with slender stems that trail and spread along the ground rather than standing upright. The leaves are clover-like, each divided into three rounded leaflets 0.3-0.8 inch (8-20 mm) long with finely toothed tips and often a faint pale or dark marking. Small yellow pea-type flowers 0.15-0.25 inch (4-6 mm) long appear singly or in clusters of two to five from late winter through spring. Each flower forms a tightly coiled, flattened seed pod 0.2-0.3 inch (5-8 mm) wide, spiraled into two to six turns and edged with curved or hooked spines that cling to fur, wool, and clothing and carry the seed to new ground. Like other legumes, the roots host nitrogen-fixing bacteria and enrich the soil. The plant grows quickly on disturbed ground, lawns, fields, and roadsides, completing its cycle before summer drought. The barbed burs are its main drawback, fouling wool and matting in pet coats, and dense stands can crowd lawns and pastures.

Native Range

Medicago polymorpha is native to the Mediterranean Basin and southern and central Europe, extending into western Asia and North Africa. It has naturalized widely in North America, South America, Australia, and other mild-winter regions as a weed.

Suggested Uses

Used at times as a cool-season cover crop and forage legume that fixes nitrogen and supplies winter grazing. In gardens and lawns it appears mostly as a weed valued more for soil improvement than for ornament. The early flowers draw bees seeking pollen and nectar before many other plants bloom.

How to Identify

Identify bur clover by its ground-hugging stems and clover-like leaves of three toothed leaflets, often marked with a small pale or dark spot. Tiny yellow pea flowers in clusters of two to five appear in late winter and spring. The fruit is a tightly coiled, spiny burr 0.2-0.3 inch (5-8 mm) wide that clings to fur and clothing, separating it from true clovers, which lack spiny coiled pods.

Appearance

Size & Dimensions

Height4" - 1'

Width/Spread1' - 2'

Colors

Flower Colors

yellow

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~8 weeks

Winter Spring

Flowering runs from late winter through spring, roughly February to May in mild-winter climates. The small yellow flowers open over several weeks as the stems lengthen. Flowering overlaps the rapid formation of the coiled spiny burs, which ripen and harden as the plant matures.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 6-10 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 Range6.0 - 8.0(Neutral)

357912

Soil Types

clay loam sand

Drainagewell drained

Water & Climate

Water Needs

Low

Care & Maintenance

Care Guide

Medicago polymorpha grows in full sun on a wide range of soils, from sandy to clay, at a pH of about 6.0-8.0, and tolerates the alkaline soils common in dry regions. It germinates with fall and winter rains, grows fast through the cool season, and sets seed before summer heat. The plant needs no irrigation where winter rainfall is reliable and little or no fertilizer because its roots fix nitrogen. In lawns and pastures, mowing before the burs harden reduces the spiny seed crop and limits spread. As a winter annual, it dies back with summer drought, leaving the hardened burs behind.

Pruning

Pruning is not part of growing this annual. Mowing or close cutting in spring, before the burs ripen, is the main way to limit seed set and spread. Spent plants break down on their own as the season ends.