Chorispora spp.

blue mustard

Brassicaceae Southwestern and central Asia

HardinessZones 4–8

Overview

Chorispora spp. is a genus of about eleven annual, biennial, and perennial herbs in the mustard family, Brassicaceae, native to the dry steppes and mountains of southwestern and central Asia. Plants range from low alpine perennials a few inches high to weedy annuals 6-20 inches (15-50 cm) tall, with lobed or toothed basal leaves and glandular-hairy stems. The four-petalled flowers, typical of the mustard family, are purple, violet-blue, or yellow and held in loose clusters; in C. tenella, the blue mustard, they open in early spring on a winter-annual rosette. A characteristic feature is the jointed, beaked seedpod that breaks crosswise into one-seeded segments rather than splitting lengthwise like most mustards. C. tenella has naturalized as an agricultural weed across North America, where its early bloom and pungent scent are noticeable in fields and disturbed ground. Alpine species such as C. bungeana grow on high scree and are studied for their cold tolerance. One limitation for gardeners is that the weedy annual species self-seed heavily and have little garden use. Hardiness and habit vary across the genus, from frost-hardy alpines to cool-season annuals.

Native Range

Chorispora spp. is native to southwestern and central Asia, including Iran, the Caucasus, Afghanistan, and the Central Asian steppes and mountains. C. tenella has spread well beyond this range as a naturalized weed across temperate North America and elsewhere.

Suggested Uses

The annual C. tenella has no garden use and is treated as a weed of fields and waste ground. Alpine perennial species are grown by specialist rock-garden and alpine-house enthusiasts. The remaining species are seldom cultivated.

How to Identify

Identify Chorispora spp. by its four-petalled mustard flowers in purple to violet-blue or yellow above glandular-hairy, lobed leaves. The clearest mark is the seedpod, which is jointed and beaked and breaks crosswise into single-seeded segments instead of splitting open lengthwise. In C. tenella, a low rosette and early-spring blue flowers in disturbed ground identify it.

Appearance

Size & Dimensions

Height6" - 1'8"

Width/Spread4" - 1'

Colors

Flower Colors

Foliage Colors

Bloom Information

Bloom Period

~4 weeks

Spring

Flowering is mainly in spring; C. tenella blooms in early spring, roughly March to May, from an overwintered rosette. Alpine perennial species flower in early summer as snow clears at high elevation. Bloom is brief in the annual species, which set seed quickly and die back.

Detailed Descriptions

Flower Description

purple to violet-blue or yellow

Foliage Description

grey-green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 6-12 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 Range6.0 - 8.0(Neutral)

357912

Soil Types

loam sand rocky

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Most Chorispora spp. are not deliberately cultivated. The annual C. tenella grows in any open, disturbed soil in full sun and completes its life cycle in spring, needing no care. Alpine perennial species require gritty, sharply drained soil, full sun, and cool conditions, and resent summer heat and wet. Where the weedy annuals appear in gardens, removing plants before seed set limits their spread. The genus tolerates poor soils and cold but not waterlogging. None need feeding.

Pruning

No pruning applies to the annual species, which die after flowering. Alpine perennial forms need only the removal of spent flower stems and dead foliage. Self-sown seedlings of the weedy species can be pulled to prevent colonization.