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Blue Oak

Quercus douglasii

Also listed as Quercus ransomii

tree☀️ full sun💧 low water❄ Hardy: Zone 8a – Zone 10b

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A native California oak with distinctive blue-gray foliage and a wide, spreading crown. Highly drought-tolerant and ideal for dry landscapes, it produces acorns that support local wildlife.

Why grow it

Blue oak outperforms most California natives in extremely dry foothill and interior valley settings where water availability is severely limited. Compared to coast live oak or valley oak, it requires less summer water once established and tolerates more extreme heat and poor soil conditions. It provides reliable acorn production for wildlife and creates dappled shade typical of open oak woodlands, making it useful for understory plantings in water-conscious California gardens.

Watch out for

Young trees benefit from consistent moisture during their first two to three growing seasons despite the species' eventual drought tolerance, requiring initial irrigation in most climates. Growth rates can be slower than some competing oak species, and the spreading crown form needs adequate space to develop without competition or pruning conflicts with structures or power lines.

Overview

Form
spreading, rounded crown
Growth Rate
slow
Size
30–60′ tall × 30–50′ wide
Dormancy
deciduous
Family
Fagaceae
Biomass and mulchWindbreak
Coppicing

Native to the United States

Native Range

California (Sierra Nevada foothills and interior valleys)

Native to: California

Seasonality

Season of Interest

SpringFall

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Companion Planting

Plants well with