Asclepias fascicularis
narrow-leaf milkweed
Western United States from Washington to Baja California
Attracts PollinatorsAttracts ButterfliesDeer ResistantDrought TolerantContainer Friendly
Native to North America
Overview
Asclepias fascicularis is a clump-forming herbaceous perennial reaching 12-48 inches (30-120 cm) tall and 18-30 inches (45-75 cm) wide via short rhizomes. Stems erect, slender, glabrous, exuding milky white latex when broken. Leaves linear-lanceolate, 2-5 inches (5-13 cm) long and 0.1-0.3 inch (3-8 mm) wide, arranged in whorls of 3-6 along the stem; upper surface dull green, lower surface paler, both glabrous. Flowers in flat-topped umbels of 10-25 small flowers at the top of the plant; each flower 0.3-0.4 inch (8-10 mm) across, with 5 reflexed petals pale lavender, pink, or greenish-white surrounding 5 erect hoods. Bloom June through September across the range. Seed pods (follicles) narrow, 2.5-4 inches (6-10 cm) long, splitting in fall to release flat brown seeds with white silky pappus for wind dispersal. Spreads 2-4 inches (5-10 cm) per year by rhizomes; clumps reach 18-30 inches (45-75 cm) wide within 3-4 years. Larval host for monarch butterfly (Danaus plexippus) in California and the western United States. Foliage dies back to ground level after first hard frost; plants resprout from rhizomes in spring. All parts contain cardenolides; ingestion by livestock is a documented cause of death in dry-range pastures.
Native Range
Native to western North America from southern Washington and Oregon south through California to northern Baja California, east to western Idaho, Nevada, Utah, and Arizona. Found in dry meadows, roadsides, pastures, foothill grasslands, and oak woodland clearings at 100-7,500 feet (30-2,300 m) elevation. Tolerates a broad range of soil conditions including disturbed, compacted, and clay soils.Suggested Uses
Planted in pollinator gardens, monarch waystations, and dry meadow plantings at 18-24 inch (45-60 cm) spacing in zones 6-10. Used in roadside and rangeland restoration across the Intermountain West. Container culture is short-lived but the species can be grown in 5-gallon (19 L) containers for 2-3 seasons before transplanting in-ground.How to Identify
Appearance
Size & Dimensions
Height1' - 4'
Width/Spread1'6" - 2'6"
Reaches mature size in approximately 3 years
Bloom Information
June through September across most of the range, with peak bloom in July and August. In zones 9-10, bloom may begin in late May and continue into October. Individual umbels last 2-3 weeks; each plant produces 5-15 sequential umbels for a total bloom of 8-12 weeks. Bloom is reduced after very dry winters.
Detailed Descriptions
Flower Description
Pale lavender-pink to greenish-whiteFoliage Description
Dull greenGrowing Conditions
Sun Requirements
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
Care & Maintenance
Care Guide
Plants establish from seed sown in fall outdoors with cold stratification, or from container stock spaced 18-24 inches (45-60 cm) apart in spring. First-year plants are slow to establish; mature size is reached in 2-3 years. Mature plants tolerate 8-12 weeks without water in zones 8-10. Container plants are short-lived (2-3 seasons) due to taproot disruption. Aphids (Aphis nerii — oleander aphid) colonize new growth in summer; populations are usually controlled by beneficial insects. Monarch caterpillars consume foliage in mid-summer and may defoliate plants temporarily; plants resprout. All parts contain cardenolides; livestock losses are a documented hazard in pasture and rangeland.Pruning
Cut stems to ground level in late fall after first hard frost or in early spring before new growth emerges. Deadhead spent umbels through summer to reduce self-seeding and to extend bloom by 2-3 weeks; alternatively, leave for fall seed dispersal in habitat plantings. Damaged stems exude milky latex when cut; latex causes skin irritation in sensitive individuals.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
fallearly spring
Container Growing
✓ Suitable for container growing
Minimum container size: 5 gallons