American Willowherb
Epilobium ciliatum subsp. ciliatum
Care
full sun
low
2–6ft tall
Prized
Throughout California in moist riparian areas, seeps, and wetlands from sea level to 10000 ft elevation, extending to British Columbia.
Care Guide
Planting
Plant American Willowherb in full sun where it can reach its mature height of 2–6 feet. This species thrives in moist conditions and adapts to various soil types, so choose a location with consistent moisture - near a rain garden, streamside area, or where water naturally collects. Space plants to account for their clumping growth habit and full size at maturity. Plant in spring or fall to give the plant time to establish before extreme temperatures.
After Planting
Water regularly during the first growing season to keep soil consistently moist, then gradually reduce watering frequency as the plant establishes - though American Willowherb tolerates a range from low to high water availability once mature. This is a clumping perennial that will grow vigorously in year one; allow it to develop its natural form rather than aggressive pruning. The plant may self-seed in ideal conditions, so deadhead spent flowers if you want to prevent volunteer seedlings in your garden.
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Endangered & Threatened Species Supported
California Threatened; Species of Special Concern
Wildlife Supported
Birds
Seed-feeding specialist during cool season
Seeds consumed during winter months in California mountains and high desert
Year-round Californian seed-feeder on Epilobium and other herbaceous plants
Opportunistic seed forager; year-round in California
Insects
Larval host plant; caterpillars feed on Epilobium foliage
Host-specific aphid; specialist herbivore on Epilobium sap
Specialist lepidopteran; larvae mine or feed within Epilobium tissues
Adult butterfly visits Epilobium flowers for nectar
Larvae feed on Epilobium; multiple generations throughout growing season