What to Plant Under Western Native Oak Trees
Keep your tree healthy by underplanting with ground covers, grasses, perennials and shrubs that thrive in dry summer conditions
Western oak trees are some of the most majestic trees in the natural landscape, with a broad canopy, gnarled branches and mottled gray bark. With a few planting considerations, native oaks can thrive in West Coast gardens, growing for decades to make excellent shade trees.
But figuring out what to plant under native oaks can be a bit of a challenge to gardeners. Western native oaks flourish in a Mediterranean climate of wet winters and long, dry summers. Most ornamental bedding plants can’t tolerate months without water, but supplying summer irrigation can increase the presence of the soil-borne fungus Armillaria mellea, which causes oak root rot.
But figuring out what to plant under native oaks can be a bit of a challenge to gardeners. Western native oaks flourish in a Mediterranean climate of wet winters and long, dry summers. Most ornamental bedding plants can’t tolerate months without water, but supplying summer irrigation can increase the presence of the soil-borne fungus Armillaria mellea, which causes oak root rot.
Ground covers. For a carpet of greenery under oaks, plant low-growing ground covers that tolerate partial shade and little moisture during the summer.
Beach strawberry (Fragaria chiloensis, USDA zones 4 to 9; find your zone), pictured here, is native to bluffs along the West Coast. It spreads to form a dense ground cover with dark leaves, white flowers and small red strawberries.
Low-growing ‘Monterey Carpet’ Hooker’s manzanita (Arctostaphylos hookeri ‘Monterey Carpet’, zones 9 and 10) is another good choice that is also native to California. It grows to be 1 foot tall by 4 to 6 feet wide, with bright green leaves tinged with red.
Other ground covers for oaks include Australian native bluebell creeper (Sollya heterophylla, zones 10 and 11), West Coast native creeping barberry (Mahonia repens, zones 5 to 9), California native creeping sage (Salvia sonomensis, zones 7 to 10) and low-growing rock cotoneaster (Cotoneaster horizontalis, zones 5 to 7).
Beach strawberry (Fragaria chiloensis, USDA zones 4 to 9; find your zone), pictured here, is native to bluffs along the West Coast. It spreads to form a dense ground cover with dark leaves, white flowers and small red strawberries.
Low-growing ‘Monterey Carpet’ Hooker’s manzanita (Arctostaphylos hookeri ‘Monterey Carpet’, zones 9 and 10) is another good choice that is also native to California. It grows to be 1 foot tall by 4 to 6 feet wide, with bright green leaves tinged with red.
Other ground covers for oaks include Australian native bluebell creeper (Sollya heterophylla, zones 10 and 11), West Coast native creeping barberry (Mahonia repens, zones 5 to 9), California native creeping sage (Salvia sonomensis, zones 7 to 10) and low-growing rock cotoneaster (Cotoneaster horizontalis, zones 5 to 7).
Flowering bulbs. Many spring-flowering bulbs grow well in dry-shade conditions and need no summer water when the plants go dormant after they bloom. For a particularly showy spring display, plant swaths of crocus, narcissus and Muscari. Gently throw a bag of bulbs under an oak tree and plant them where they land to create a natural-looking drift.
For West Coast native bulbs, turn to native species of allium, Brodiaea, Calochortus, Fritillaria and Lilium, which can be found at well-stocked native-plant nurseries.
7 Bulbs That Flourish in Mild Climates
For West Coast native bulbs, turn to native species of allium, Brodiaea, Calochortus, Fritillaria and Lilium, which can be found at well-stocked native-plant nurseries.
7 Bulbs That Flourish in Mild Climates
Ornamental and native grasses. Mimic the look of the oak woodlands of the coastal range by underplanting oak trees with native grasses and noninvasive ornamental grasses. Blue oat grass (Helictotrichon sempervirens, zones 4 to 8), shown, is noninvasive and grows in fountain-like clumps 2 to 3 feet tall and wide. Plant en masse to form a sea of blue-green under trees.
Other options for grasses that thrive under and around oaks include western U.S. natives blue wild rye (Elymus glaucus, zones 4 to 8), deer grass (Muhlenbergia rigens, zones 7 to 11) and tufted hairgrass (Deschampsia cespitosa, zones 4 to 9).
Other options for grasses that thrive under and around oaks include western U.S. natives blue wild rye (Elymus glaucus, zones 4 to 8), deer grass (Muhlenbergia rigens, zones 7 to 11) and tufted hairgrass (Deschampsia cespitosa, zones 4 to 9).
Ferns. Ferns are a natural choice to plant under oaks, as these understory plants grow well in shady areas, and many can tolerate low summer water. The California Oaks project recommends four varieties in particular for planting under oaks: autumn fern (Dryopteris erythrosora, zones 6 to 9), coastal wood fern (D. arguta, zones 7 to 10), narrow sword fern (Nephrolepis cordifolia, zones 8 to 10) and native western sword fern (Polystichum munitum, zones 3 to 10).
Perennials. In areas beneath the oak canopy that receive full shade to partial shade, plant Bergenia (Bergenia crassifolia, zones 2 to 9), bear’s breech (Acanthus mollis, zones 7 to 11) and cast iron plant (Aspidistra elatior, zones 7 to 11).
‘Autumn Bride’ coral bells (Heuchera villosa ‘Autumn Bride’, zones 4 to 9), shown here, grow in clumps with attractive ruffled foliage and white to pale pink flowers in early spring.
‘Autumn Bride’ coral bells (Heuchera villosa ‘Autumn Bride’, zones 4 to 9), shown here, grow in clumps with attractive ruffled foliage and white to pale pink flowers in early spring.
For planting beds that extend outside the drip line, choose plants that prefer partial sun to full sun and need little irrigation in the summer.
California buckwheat (Eriogonum fasciculatum, zones 6 to 10), shown here, is native to West Coast canyons and woodlands and is drought-tolerant enough to grow well in dry summers. Other low-water, sun-loving perennials that would work well planted near oaks include native beach wormwood (Artemisia pycnocephala, zones 4 to 9), catmint (Nepeta faassenii, zones 4 to 9), Perez’s sea lavender (Limonium perezii, zones 10 and 11) and woolly yarrow (Achillea tomentosa, zones 2 to 9).
California buckwheat (Eriogonum fasciculatum, zones 6 to 10), shown here, is native to West Coast canyons and woodlands and is drought-tolerant enough to grow well in dry summers. Other low-water, sun-loving perennials that would work well planted near oaks include native beach wormwood (Artemisia pycnocephala, zones 4 to 9), catmint (Nepeta faassenii, zones 4 to 9), Perez’s sea lavender (Limonium perezii, zones 10 and 11) and woolly yarrow (Achillea tomentosa, zones 2 to 9).
Shrubs. Under the shady oak canopy, turn to woodland native shrubs such as pink chaparral currant (Ribes malvaceum, zones 7 to 10), which is native to the California Coast Ranges and Sierra foothills. The pendulous pink flowers are followed by small fruits favored by birds.
Other partial-shade plants to consider include Oregon grape (Mahonia aquifolium, zones 5 to 9), California wax myrtle (Myrica californica, zones 7 to 10) and fragrant sweetbox (Sarcococca ruscifolia, zones 7 to 9).
Other partial-shade plants to consider include Oregon grape (Mahonia aquifolium, zones 5 to 9), California wax myrtle (Myrica californica, zones 7 to 10) and fragrant sweetbox (Sarcococca ruscifolia, zones 7 to 9).
Beyond the oak’s canopy, plant California wild rose (Rosa californica, zones 7 to 10) for lovely flowers in summer and decorative rose hip clusters in autumn. Other plants that work well in partial sun to full sun around oaks include big berry manzanita (Arctostaphylos glauca, zones 7 to 10), California wild lilac (Ceanothus spp.), Cleveland sage (Salvia clevelandii, zones 8 to 11), coffeeberry (Rhamnus californica, zones 7 to 10) and hollyleaf cherry (Prunus ilicifolia, zones 7 to 10).
Vines. Allow trailing vines to ramble under oak trees for a natural, uncontrolled look. California wild grape (Vitis californica, zones 7 to 10) is a particularly good choice, as it provides dramatic fall foliage color and supports wildlife with semisweet grapes. Other native West Coast vines to plant under and around oaks include pipestem clematis (Clematis lasiantha, zones 5 to 10), pink honeysuckle (Lonicera hispidula, zones 7 to 9) and western white clematis (Clematis ligusticifolia, zones 5 to 10).
Keep planting to a minimum. Another strategy for what to put under western oaks is to nearly skip plants altogether. Spreading wood chip mulch, decomposed granite or pea gravel beneath part of an oak’s canopy can cut down on planting beds needing irrigation.
Turn the shady area into an inviting destination with a pair of chairs or an outdoor table. Given that gravel can compact soil and reduce the oxygen available to oak roots, it’s best to limit the amount of ground covered with gravel to less than half of the area under a tree’s canopy.
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Discover more ground covers for your garden
Turn the shady area into an inviting destination with a pair of chairs or an outdoor table. Given that gravel can compact soil and reduce the oxygen available to oak roots, it’s best to limit the amount of ground covered with gravel to less than half of the area under a tree’s canopy.
Not on the West Coast? Celebrate Eastern Oaks for Wildlife, Longevity and Seasonal Interest
More
8 Reasons to Plant a Great Tree
Discover more ground covers for your garden
Here are a handful of recommended ground covers, bulbs, grasses, perennials, shrubs and vines gleaned from native-plant societies and California Oaks, a project of the California Wildlife Foundation, for plants that thrive under these majestic trees.