Streptanthus spp.

jewelflower

Attracts Pollinators Attracts Butterflies Deer Resistant Drought Tolerant

HardinessZones 7–9

Overview

Streptanthus is a genus of about 35 species of annual and perennial herbs in the mustard family (Brassicaceae), native to western North America and centered in California. Known as jewelflowers or twistflowers, the plants grow 8-40 inches (20-100 cm) tall on slender, often glaucous stems with clasping, sometimes perfoliate upper leaves. The flowers stand apart within the family: an inflated, urn-shaped calyx encloses narrow, crisped or twisted petals in shades of purple, maroon, white, cream, or yellow-green, opening from the base of the raceme upward. Many species are restricted to serpentine, gabbro, or other harsh mineral soils, and the genus includes numerous narrow endemics. Slender curved seed pods (siliques) follow and split to release flattened seeds. Streptanthus grows in full sun on rocky, sharply drained, often nutrient-poor or metal-rich soils in chaparral, woodland openings, and montane slopes. Annual species complete their cycle in a single wet season, while perennials persist from a woody base. The genus tolerates lean, dry ground but is short-lived in rich garden soil and intolerant of summer irrigation.

Native Range

Streptanthus is native to western North America, with the greatest diversity in California and adjacent Oregon, Nevada, and the desert Southwest. Many species are edaphic endemics confined to serpentine, gabbro, or limestone outcrops in chaparral, oak woodland, and montane slopes.

Suggested Uses

Streptanthus is used in native plant, rock, and dry-meadow gardens in western regions, and in restoration of serpentine and chaparral habitats. Its inflated flowers feature in wildflower and pollinator plantings on lean soils. It suits gravel gardens where summer water is withheld.

How to Identify

Identify Streptanthus by its inflated, urn-shaped flower buds and calyces enclosing narrow, often crisped petals in purple, maroon, white, or yellow-green. The upper stem leaves typically clasp or pierce the stem and the foliage is often glaucous blue-green. Slender curved seed pods and an association with serpentine or other rocky mineral soils help confirm the genus.

Appearance

Size & Dimensions

Height8" - 3'4"

Width/Spread6" - 1'6"

Colors

Flower Colors

Foliage Colors

Bloom Information

Bloom Period

~6 weeks

Spring Summer

Flowering runs from spring into early summer, generally March to June, earlier in low deserts and later at elevation. Flowers open in sequence up the raceme over several weeks. In annual species the plant dies after seed set, while perennials rebloom from the base in following years.

Detailed Descriptions

Flower Description

purple to maroon, white, or yellow-green

Foliage Description

blue-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

rocky sand loam

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

1-2 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Streptanthus grows in full sun on sharply drained, rocky, and nutrient-poor soils, including serpentine and other mineral substrates. Water needs are low, and plants are adapted to dry summers after spring growth. Rich soil, shade, or summer watering shortens their life and weakens growth. Soil pH ranges from about 6.0 to 8.0 across the genus. Annual species are grown from seed sown in autumn or early spring where they are to grow, since they transplant poorly. Most perennials are hardy in roughly USDA zones 7-9 and tolerate little root disturbance.

Pruning

Pruning is minimal. Spent stems of annual species are cleared after seed drop, and perennials can be cut back after flowering to tidy growth. Self-sown seedlings are easily thinned where spread is not wanted.