Oak trees are a symbol of both strength and beauty. There is a variety of Oak appropriate for just about any garden. Some grow in dry, high desert, while other species are better suited for hot and humid conditions. In the home landscape, oak trees are often either several decades old and fully mature or newly planted sapling. Either type can be grown with companion plants to give your landscape a unified and lush appearance.
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All Oak trees thrive in full sun and well-draining soil; however, the plants that grow around Oaks must be able to tolerate partial or full shade and dry soil conditions. Turf grasses are not well-suited for this role. Choosing plants that thrive in dry shade will save you many hours of work and will result in a much more eco-friendly landscape.
Shrubs To Plant With Oak Trees
The roots of Oak trees are susceptible to damage from deep digging or excess watering. Space any shrubs at least 4-6 feet from the base of an old, established tree. Native or shallow-rooted shrubs, such as ceanothus, manzanita, mahonia, flannel bush, and snowberry, are a safe bet to plant with Oak trees. These natives will establish well in dry soil and partial shade near large Oak trees.
Newly planted Oaks may be underplanted with deeper-rooted shrubs, which can establish at the same rate as the Oak. Hydrangeas (especially the Oakleaf Hydrangea), holly, and azaleas are good choices for climates that have moderate rain throughout the summer. Once the plants become established, supplemental watering wouldn't be needed.
Perennials To Plant With Oak Trees
Oak trees are often semi-evergreen, losing their leaves for only a short period of time before new growth emerges. Early spring ephemeral perennials and bulbs fare well under oak trees and take advantage of the increased sun exposure before the Oak leafs out in the spring. Some of the easiest bulbs include snakehead fritillaria, crocus, smaller species daffodils, English bluebells, and grape hyacinth. Ground covers like sweet woodruff, wood violets, and foamflower will also spread and grow well in shallow soil near tree roots. Use clumping sedges to replace the lush look of a lawn under an Oak tree. For color, hardy salvias will continue to bloom under an Oak for months until autumn.
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Annuals To Plant With Oak Trees
Annuals are a great solution for adding color under and near Oak trees. Select annuals with shallow roots and long blooming periods like nasturtium, California poppy, and wax begonia, which make effective ground covers under an Oak. Finely textured annual grasses like fountain grass and feather grass will give the whole design a modern and minimalist feel.
Make sure that any annual tolerates part shade and will thrive in drier soils. Supplemental watering can be done carefully at planting and through the growing season with either soaker hoses or drip irrigation. Avoid oscillating or overhead sprinklers, as repeated watering of the tree trunk will cause damage over time and can even lead to an early death.
Best Companion Plants For Oak Trees in Containers
Oak trees are typically too large to grow successfully in a container. However, containers are a great way to grow other plants under the dripline of an Oak tree. Select perennials that require minimal watering and grow well in partial shade, such as succulents, thyme, and lamb ears. For annuals, look for shade lovers such as caladiums, impatiens, tuberous begonias, wishbone flowers, and fuchsia You can overwinter a container with begonias, caladiums, and fuchsia in a frost-free spot through the winter.
Photo by K M, unmodified, Flickr, copyright CC BY 2.0 DEED
Plants Not To Grow With Oak Trees
Excess watering can damage Oak trees established in drier soil. Moisture-loving plants, such as woodland ferns, hostas, gunnera, and common turf grasses will only grow well under Oaks with supplemental irrigation. These plants will grow slowly and may eventually die out under an Oak. Also avoid planting sun-loving shrubs such as spirea, weigela, and native roses. These shrubs will not bloom and thrive in the dry shade of an Oak tree.
Best Plants To Grow With Oak Trees
Oak trees are an important keystone species for the ecosystem. Plant them with native plants that will similarly support wildlife and grow easily in your climate. Shallow-rooted annuals and perennials tolerant of dry shade make ideal companions for Oak trees. Quick-growing groundcovers and shady bedding annuals will fill in under the Oak without harming the tree.
Sources: “Planting Under Oaks.” UC Master Gardener Program of Sonoma County. sonomamg.uncanr.edu