Mt. Diablo Helianthella
Helianthella castanea
Care
full sun
2–2ft tall
Mar-May
Friendly
Prized
East Bay hills, endemic to the Mt. Diablo region of Contra Costa County, between 1000-3000 ft elevation in grassland and oak woodland.
Care Guide
Planting
Plant Mt. Diablo Helianthella in full sun where it will thrive during its spring blooming season (March–May). This rare endemic plant grows 2 feet tall and spreads in clumps, so give it room to expand. While specific soil and drainage requirements aren't documented, this native species evolved on Mount Diablo's rocky terrain, suggesting it likely tolerates lean, well-draining conditions.
After Planting
The data provided doesn't specify an establishment watering schedule, pruning needs, or dormancy behavior for this rare plant. Your best bet is to observe how it performs through its first year - watch for signs of stress or vigor that will guide your watering decisions in subsequent seasons. Since it's a spring bloomer and perennial herb endemic to our local area, connecting with native plant nurseries or Mount Diablo State Park resources may provide the most reliable care guidance.
Visit Calscape for more information about Mt. Diablo Helianthella
Wildlife Supported
Insects
Larval host plant; caterpillars feed on foliage April-June
Foraging on flowers during bloom period
Larval and adult feeding on plant tissues during growing season
Nectar and pollen collection during flowering
Native bee visitation during peak blooming mid-summer
Birds
Seed consumption, particularly important in winter food-scarce periods
Seed foraging during fall migration and winter months