Rapistrum rugosum (annual bastard cabbage)

Rapistrum spp.

Europe, Mediterranean, North Africa, and western and central Asia

Overview

Rapistrum spp. is a small genus of herbaceous plants in the family Brassicaceae, native to Europe, the Mediterranean, and western Asia, with Rapistrum rugosum the most widespread species. Plants are annual to short-lived perennial, growing 1-5 feet (30-150 cm) tall from a basal rosette, with branched, bristly-haired stems. The lower leaves are 2-8 inches (5-20 cm) long, lyre-shaped with a large terminal lobe and smaller side lobes, while upper leaves are smaller and narrower. Yellow flowers about 0.2-0.4 inch (5-10 mm) across have four petals in a cross and are carried in elongating clusters at the stem tips through spring and summer. The fruit is a two-jointed pod: a narrow lower segment topped by a rounded, ribbed upper segment holding one seed, the whole breaking apart at maturity. A single vigorous plant can produce thousands of seeds. Growth is rapid in fertile, disturbed soil, and plants can form dense stands that crowd out low vegetation. Foliage and stems die back after seed set. Several species are naturalized well beyond their native range and behave as agricultural and roadside weeds.

Native Range

Rapistrum spp. is native to Europe, the Mediterranean Basin, North Africa, and western and central Asia. Plants grow in disturbed and cultivated ground, field margins, roadsides, and waste places on fertile, well-drained soils. Rapistrum rugosum has naturalized across North and South America, Australia, and southern Africa, where it spreads along roadsides and into crop fields.

Suggested Uses

Rarely planted by choice and encountered mainly as a volunteer in disturbed ground, field edges, and roadsides. Where present in wildflower or forage settings it produces early-season yellow bloom, but its heavy seeding and weedy spread limit deliberate use. Management often focuses on removal before seed set.

How to Identify

Recognized by yellow four-petaled flowers and, most reliably, by the two-segmented fruit, in which a small ribbed, beadlike upper joint sits on a slender lower joint and snaps off whole. Lower leaves are lyre-shaped with a large end lobe, and stems are roughly hairy. Rapistrum rugosum differs from similar yellow mustards such as Sinapis spp. and Brassica spp. by this jointed, breaking fruit.

Appearance

Size & Dimensions

Height1' - 5'

Width/Spread8" - 2'

Colors

Flower Colors

yellow

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~12 weeks

Spring Summer

Flowers from spring into summer, mainly April through August, with the start depending on whether plants germinate in autumn or spring. Autumn-germinated plants bloom earlier and grow larger. Flowering continues over many weeks as the clusters lengthen, and seed ripens from early summer onward.

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 - 7.5(Neutral)

357912

Soil Types

loam clay sand

Drainagewell drained

Water & Climate

Water Needs

Low

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Plants grow readily from seed on fertile, disturbed, well-drained soil in full sun and need little attention once established. Growth is fastest with moisture and high soil fertility, and plants tolerate short dry periods by maturing quickly. Self-seeding is heavy, and volunteer seedlings appear in large numbers where seed is allowed to drop. Removing plants before the pods ripen limits spread. Flea beetles and cabbage-family pests may feed on the leaves. In many regions Rapistrum rugosum is treated as a weed and is subject to control along roads and in fields.