North America Native Plant

Humboldt Bay Owl’s-clover

Botanical name: Castilleja ambigua humboldtiensis

USDA symbol: CAAMH

Life cycle: annual

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Orthocarpus castillejoides Benth. var. humboldtiensis D.D. Keck (ORCAH)   

Humboldt Bay Owl’s-Clover: A Rare Coastal California Gem Worth Growing Responsibly If you’re passionate about native California plants and have a soft spot for rare wildflowers, Humboldt Bay owl’s-clover (Castilleja ambigua humboldtiensis) might just capture your heart. This charming annual brings a splash of color to coastal gardens while supporting ...

Rare plant alert!

Region: Conservation status by state

Status: S4T2: Status is uncertain but is somewhere between the following rankings: Subspecies or variety is imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 6 to 20 occurrences or few remaining individuals (1,000 to 3,000) ⚘ Apparently Secure: Uncommon but not rare, and usually widespread. Possibly cause for longterm concern. Typically more than 100 occurrences in the state or more than 10,000 individuals ⚘

Humboldt Bay Owl’s-Clover: A Rare Coastal California Gem Worth Growing Responsibly

If you’re passionate about native California plants and have a soft spot for rare wildflowers, Humboldt Bay owl’s-clover (Castilleja ambigua humboldtiensis) might just capture your heart. This charming annual brings a splash of color to coastal gardens while supporting local pollinators, but there’s an important catch every gardener should know about before planting.

What Makes This Plant Special

Humboldt Bay owl’s-clover is a delightful annual forb that belongs to the paintbrush family. True to its name, this wildflower calls the coastal regions around Humboldt Bay in Northern California home. As an annual plant, it completes its entire life cycle in just one growing season, producing seeds before winter arrives.

The plant showcases the classic paintbrush flower form with small, tubular blooms that cluster together in colorful displays. These flowers typically appear in lovely shades of yellow, pink, or purple, creating eye-catching patches in their natural coastal meadow habitats.

Where You’ll Find It Growing Wild

This special wildflower is native to California, specifically thriving in the coastal areas of the northern part of the state. Its natural range centers around the Humboldt Bay region, where it has adapted to the unique conditions of coastal meadows and grasslands.

A Word of Caution: Rarity Matters

Here’s where responsible gardening becomes crucial. Humboldt Bay owl’s-clover has a conservation status that indicates it’s quite rare in the wild. This means that while it’s absolutely worth growing, you’ll want to be extra careful about where you source your seeds or plants.

Always purchase from reputable native plant nurseries that ethically propagate their stock rather than collecting from wild populations. Never collect seeds or plants from the wild yourself, as this can harm already vulnerable populations.

Why Gardeners Love (and Should Grow) This Plant

Despite its rarity concerns, there are compelling reasons to include Humboldt Bay owl’s-clover in your garden:

  • Pollinator magnet: Those tubular flowers are perfectly designed to attract hummingbirds and native bees
  • Low maintenance: As an annual, it doesn’t require long-term care commitments
  • Authentic coastal character: Adds genuine local flavor to Northern California native gardens
  • Conservation value: Growing it responsibly helps preserve genetic diversity

Perfect Garden Settings

This coastal beauty shines brightest in:

  • Native wildflower gardens
  • Coastal-themed landscapes
  • Naturalized meadow areas
  • Pollinator gardens
  • Rock gardens with good drainage

Growing Conditions and Care

Humboldt Bay owl’s-clover thrives in USDA hardiness zones 9-10, which makes sense given its coastal California origins. The plant prefers:

  • Sunlight: Partial sun to full sun exposure
  • Soil: Well-draining soils that don’t stay waterlogged
  • Climate: Coastal conditions with mild, wet winters and dry summers

Planting and Care Tips

Success with this annual wildflower comes from working with its natural rhythm:

  • Timing: Direct seed in fall to allow natural winter stratification
  • Planting: Scatter seeds on prepared soil surface and lightly rake in
  • Watering: Rely on natural winter rains; minimal summer watering needed
  • Maintenance: Allow plants to set seed naturally to encourage self-seeding

Remember, as an annual, these plants will die back after producing seeds, but they’ll likely return the following year if conditions remain favorable.

Supporting Conservation Through Gardening

By choosing to grow Humboldt Bay owl’s-clover responsibly, you’re participating in grassroots conservation efforts. Your garden becomes a small sanctuary that helps maintain genetic diversity while providing habitat for the pollinators this plant has co-evolved with over thousands of years.

Just remember: source ethically, grow proudly, and let this little coastal treasure remind you of California’s incredible native plant heritage every time those colorful blooms appear in your garden.

Humboldt Bay Owl’s-clover

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Asteridae

Order

Scrophulariales

Family

Scrophulariaceae Juss. - Figwort family

Genus

Castilleja Mutis ex L. f. - Indian paintbrush

Species

Castilleja ambigua Hook. & Arn. - johnny-nip

Plant data source: USDA, NRCS 2025. The PLANTS Database. https://plants.usda.gov,. 2/25/2025. National Plant Data Team, Greensboro, NC USA