Turritis spp.

tower mustard

Brassicaceae Temperate Northern Hemisphere

Attracts Pollinators Attracts Butterflies Drought Tolerant

Native to North America

SunFull Sun – Part Shade

WaterLow · drought-tolerant

HardinessZones 4–8

Overview

Turritis spp. is a small genus of annual to biennial herbs in the mustard family (Brassicaceae), found across Europe, Asia, and North America in dry, open habitats. The most familiar species, tower mustard (Turritis glabra), forms a basal rosette of toothed, bristly leaves in its first year and sends up a single, slender, unbranched stem 1.5-5 feet (45-150 cm) tall in the second. Stem leaves are smooth, grey-green, and clasp the stem with arrow-shaped bases. Small four-petalled flowers, pale yellow to creamy white, cluster at the stem tip and open from late spring into summer. They ripen into long, narrow seedpods called siliques that stand erect and close to the stem, giving the plant a stiff, tower-like outline. The genus grows on sandy banks, rocky slopes, roadsides, and dry grassland, often on disturbed ground. Plants are short-lived and rely on abundant seed to persist; the foliage withers soon after flowering, leaving little above ground.

Native Range

Native across the temperate Northern Hemisphere, including Europe, temperate Asia, and North America, growing in dry grassland, sandy banks, rocky slopes, and disturbed ground.

Suggested Uses

Grown in wildflower meadows, gravel gardens, and naturalistic plantings on poor, dry soils. Also useful in restoration of sandy grassland and as a larval host for some butterflies.

How to Identify

First-year plants form a basal rosette of toothed, bristly leaves; the second year sends up a tall, unbranched stem with smooth, grey-green leaves that clasp it by arrow-shaped bases. Pale yellow to cream four-petalled flowers top the stem. Narrow erect siliques press close to the stem in a tower-like column.

Appearance

Size & Dimensions

Height1'6" - 5'

Width/Spread6" - 1'

Colors

Flower Colors

Foliage Colors

Bloom Information

Bloom Period

Spring Summer

Flowering runs from late spring into midsummer, roughly May to July. The small pale flowers open in a tight terminal cluster as the stem lengthens. Erect seedpods follow and ripen through summer, splitting to shed small seed.

Detailed Descriptions

Flower Description

pale yellow to cream

Foliage Description

grey-green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

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 - 7.5(Neutral)

357912

Soil Types

sand rocky loam

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Tower mustard grows in full sun to light shade in dry, well-drained sandy or rocky soils of low fertility. It tolerates drought and poor ground and suits naturalistic and wildflower plantings rather than rich borders. As a biennial or annual it is grown from seed sown where it is to flower, and it self-sows freely on open soil. Little care is needed once seedlings establish. Flea beetles and the usual brassica pests may chew the foliage.

Pruning

No pruning is needed. Spent stems can be cut down after the seedpods ripen, though leaving some allows self-seeding to maintain the planting.

✓ Toxicity

Non-toxic

Wildflower