Blue Oak
Quercus douglasii
Last reviewed: July 2026
Quercus douglasii (Blue Oak) is a drought-tolerant California native tree that blooms March through May. This oak species thrives in full sun and supports native pollinators including bees and beetles.
Blue Oak (Quercus douglasii) is not on the ASPCA Animal Poison Control Center toxic plant list for dogs or cats (aspca.org (opens in new tab), last reviewed 2026-05-21). If your pet shows symptoms after eating any plant, call the ASPCA at (888) 426-4435.
The USDA PLANTS Database (opens in new tab) does not flag Blue Oak as toxic to livestock.
Light
full sun
Water
low
Size
300"–600" H × 300"–600" W
Bloom
Mar, Apr, May
Native to
CA
Pollinators
bees, beetles
Browse plants for this ecoregion
Blue oak is a stately native tree with distinctive blue-green foliage and a broad, rounded canopy. It grows slowly but can live for centuries, eventually reaching heights of 25-50 feet. This drought-tolerant tree adapts well to Mediterranean climate zones and requires minimal irrigation once established.
Growing Blue Oak
Grow Blue Oak in full sun and low water. Mature plants reach 300 to 600 inches tall and spread 300 to 600 inches wide. Expect moderate maintenance to keep it looking intentional in a front yard.
In an HOA neighborhood
Blue Oak is an HOA-friendly choice in the right placement. Maintenance level: moderate. Tidiness: 3 out of 5.
Works well in: street edge, mid zone.
- Mature size (25-50 feet) may exceed HOA height restrictions
- Acorn drop can create seasonal maintenance issues
- May not fit smaller front yard spaces due to spread
Wildlife value
Blue oaks support numerous wildlife species, producing acorns that feed deer, squirrels, jays, and other animals. During spring bloom months, their catkins provide important early-season pollen for bees and beetles.
Common questions
- When does Blue Oak bloom?
- Blue Oak (Quercus douglasii) blooms from March through May, producing inconspicuous flowers that attract bees and beetles.
- Where is Blue Oak native?
- Blue Oak is native to California, where it grows naturally in foothill woodlands and grasslands throughout much of the state.
- What pollinators visit Blue Oak?
- Blue Oak flowers attract various pollinators including bees and beetles, which help with the tree's reproduction cycle.
- How much water does Blue Oak need?
- Blue Oak is highly drought-tolerant and requires low water once established, making it well-adapted to California's Mediterranean climate.
- Is Blue Oak toxic to dogs?
- Blue Oak is not on the ASPCA Animal Poison Control Center toxic plant list for dogs (aspca.org).
- Is Blue Oak toxic to cats?
- Blue Oak is not on the ASPCA Animal Poison Control Center toxic plant list for cats (aspca.org).
- Is Blue Oak toxic to livestock?
- The USDA PLANTS Database does not flag Blue Oak as toxic to livestock.
- Is Blue Oak HOA-friendly?
- Blue Oak is generally an HOA-friendly choice in the right placement, with moderate maintenance.
Native range data from the USDA PLANTS Database and regional native plant society lists. Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.
Ready to grow Blue Oak? Add it to your garden in Pollinator Patch to track it and get season-by-season care guidance.
Not sure where to start? Take the 2-minute yard quiz