Trees are the most imposing aspect of a native landscape whether they dominate wildlands or open to vistas. They are also a valued aesthetic in home gardens and in urban and suburban open spaces as they provide shade from harsh sun or simply add beauty with foliage, bark, and flowers.
As climate-change advances all around, gardeners are taking a fresh look at tree selection, focusing on drought tolerance and habitat restoration over other features. Yet, it is important to keep in mind that not all California natives are drought-tolerant. Many naturally inhabit riparian areas or depend on rainfall beyond the summer-dry season in some microclimates.
Success with native trees, in short, depends on planting the right tree in the right place, satisfying the same needs where they grow naturally. When that happens, trees provide food and shelter for many species of native fauna—especially birds, butterflies, and other pollinators—and become central elements in our gardens.
Arctostaphylos manzanita ‘Dr. Hurd’—'Dr. Hurd’ manzanita. Multi-trunked ‘Dr. Hurd’ is the most tree-like manzanita, reaching 10-12 ft. high and wide—sometimes to 20 ft. or more—with evergreen foliage. Smooth, reddish brown branches that rise from low on the trunk are the main feature. Large clusters of white flowers bloom prolifically in winter, drawing many nectar-seekers such as hummingbirds and honey bees. Small, round fruits feed a diverse group of wildlife.
Ceanothus ‘Ray Hartman’. This fast-growing ceanothus bears shiny 2-3 in. dark green leaves highlighted in spring by tiny, lavender-blue flowers clustered in 3-5 in. long spikes visited by butterflies and bees. Pruning is usually needed to control a natural 15-20 ft. width and maintain an 18-20 ft. height. ‘Ray Hartman’ thrives near the coast or inland, adapting to nearly any soil type and benefiting from occasional summer irrigation.
Cercis occidentalis—western redbud. Grown as either a large shrub or small, multi-trunked tree, a blooming western redbud is one of the most dramatic of California natives and one visited by birds, butterflies, moths, and bees. Vibrant magenta flower clusters hug branches in early spring followed by heart-shaped, bluish-green leaves that turn red and yellow in autumn. After leaf fall, long, maroon, flattened seed pods persist but may be knocked from branches and swept up if they appear unattractive. In full sun in the hottest inland areas, occasional waterings during the dry season may be needed, less so in part shade or near the coast. Left unpruned, redbud grows 12-20 ft. high and wide.
Chilopsis linearis—desert willow. Native to desert washes, desert willow is named for long, narrow, willow-like foliage. It’s most attractive in summer when thin branches on multiple trunks are laden with 1-3 in. tubular blossoms that vary from white to shades of pink and deep lavender and are attractive to hummingbirds but avoided by deer. Seed pods hang during deciduous winter months. Desert willow requires full sun, thrives best in high summer heat with occasional irrigation, but does not tolerate heavy wet soil for long periods. Lower branches and basal shoots may need to be trimmed away to enhance the 12-20 ft. height and width to expose fissured and scaly bark that develops with age.
X Chitalpa tashkentensis—chitalpa. Two fast-growing hybrids of desert willow and non-native catalpa are larger than desert willow and develop more prolific blossoms. Hummingbirds are attracted to white-blooming ‘Morning Cloud’ and ‘Pink Dawn.’ Both thrive best in hot, inland areas but suffer from cooler, moist conditions near the coast.
Cornus ‘Eddie’s White Wonder’—dogwood. This hybrid of C. nuttallii, native to northern California and the Pacific Northwest and the eastern native C. florida, is superior in gardens to either species. Clusters of showy, overlapping bracts 3-4 in. across enclose tiny flowers for a spectacular spring display on layered branches. Fast-growing to 20-25 ft. and 15 ft. wide, its red fall color and red fruits—food for many bird species—rival spring blossoms. Plant in sun to light shade or afternoon shade with exposure to excellent air circulation and fast-draining soil. Once established, give occasional irrigation in summer.
Fraxinus dipetala—California ash. A slow-growing tree to 15-25 ft. and 10-20 ft. wide, California ash assumes a sculptural effect when sited in sun to light shade in an open area to enhance its multiple trunks and furrowed dark gray bark. Deciduous until late spring when clusters of small white, lilac-like flowers cascade from branch ends. Pinnate leaves turn coppery before dropping in late summer; birds are attracted to seeds. California ash is drought tolerant once established.
Heteromeles arbutifolia—toyon. Often grown as a very large shrub, toyon makes an attractive evergreen tree to 15 ft. when trained from youth with a single or multiple trunks. Dark green leathery leaves are a pleasing feature year-round, highlighted in summer by clusters of white blossoms that attract pollinators, then followed in late fall by red, holly-like berries devoured by birds. Gardeners may be discouraged by the need to prune numerous water sprouts that rise from the base, but the effort is needed to maintain the structure of a tree.
Myrica (syn. Morella) californica—Pacific wax myrtle. Early training converts this shrubby evergreen with glossy, rich green foliage into a 10-30 ft. tall and 10-12-ft. wide tree. Adaptable to most soils, myrica thrives in full, open sunlight in coastal areas but prefers afternoon shade inland. Appearance and health are enhanced with occasional irrigation when it can grow as much as 2-4 ft. a year. Plants are generally long-lived and easy-care but can suffer from thrips, spider mites, and whiteflies. Inconspicuous flowers yield purplish brown, waxy fruit attractive to birds. Deer generally ignore them.
Prunus ilicifolia ssp. ilicifolia—hollyleaf cherry. A valuable, drought-tolerant, tree 10-30 ft. high and wide, hollyleaf cherry may be purchased either as a shrub or tree and may require periodic pruning to maintain form. Main features are its glossy green foliage resembling prickly holly leaves and clusters of creamy flowers that yield small, dark, edible fruits attractive to birds. Care must be taken to provide good drainage, to keep fruit drop away from paved areas, and to irrigate occasionally in severe drought.
Aesculus californica—California buckeye. Height and width is variable, from 15-45 ft. depending on exposure and access to moisture. Showy, creamy white flower clusters 6-12 in. long dominate branch tips over fan-like leaves in spring. Silvery gray trunks often achieves a sculptural look in summer after leaf drop in response to drought and high heat. Pear-shaped or rounded fruits called buckeyes hang from bare branches until they split open in fall.
Lyonothamnus floribundus ssp. asplenifolius—fernleaf Catalina ironwood. Beautifully striated bark, fernlike foliage, and creamy white blossom clusters characterize this fast growing tree 20-40 ft. tall and about half as wide. Clusters darken and remain for a few years, which detracts somewhat, but are upstaged by the narrow profile and attractive peeling, reddish brown bark.
Parkinsonia florida (Cercidium floridum)—blue palo verde. Native to Southern California and Arizona deserts, palo verde trees need full sun and well-drained soil, best in hot interior microclimates. Long, wispy branches are covered in spring with fragrant, golden yellow blossoms visited by bees and other pollinators. Small leaves drop in high heat but the yellowish green trunk and branches create a striking silhouette on this 15-30 ft. high and wide tree. Limited summer water often produces a second round of foliage and flowers. ‘Desert Museum’ is a choice thornless cultivar.
Prunus ilicifolia ssp. lyonia—Catalina cherry. Trained as a tree, Catalina cherry grows rapidly, reaching as much as 45 ft. in ideal conditions with supplemental water. Dark green, glossy leaves have smooth or nearly smooth margins. Appearance and care is similar to lower-growing Prunus ilicifolia ssp. ilicifolia—hollyleaf cherry above.
Platanus racemosa—California sycamore. Native sycamore reaches an impressive 40-80 ft. height with half that width. Surprisingly fast growth depends on access to regular water, best along streams or in seeps. Bark is mottled gray and white on single or multiple stem; maplelike leaves darken to orange-brown in winter and hang on for months along with round seed balls. Cool, damp spring months prompt a fungal outbreak that causes leaf drop that dissipates in dry conditions. This tree is an important host for the western tiger swallowtail butterfly as well as for other butterflies and hummingbirds.
Populus fremontii ‘Nevada’—black cottonwood. Access to groundwater and nearly constant moisture in warm inland locations is critical to success and pleasure with this species. Fluttering green foliage turns pale yellow in autumn and holds on branches until dropping to reveal silvery white bark that becomes brown and furrowed with age. Rarely beyond 50 by 30 ft. in height and width in garden settings, this large tree must be carefully sited due to aggressive surface roots. ‘Nevada’ is a male cultivar that does not produce bothersome, cottony seeds but supports butterflies, moths, and birds.
Quercus agrifolia—coast live oak. Of all the native oaks, evergreen coast live oak is the most common in Sonoma County. It is estimated to support more species of fauna than any other native as one of the most important habitat species. Its large size, 35-60 ft. in height and width develops recognized character with sturdy, arching branches and leathery, spiny leaves and inch-long, conical acorns. In home gardens, this tree may consume a large part of the landscape and thrives best with only dropped leaves for mulch and no other plants under the canopy. Supplemental irrigation after planting encourages fast growth but is not needed and should be avoided in maturity.
Quercus douglasii—blue oak. One of the slowest growing oaks, the deciduous blue oak is also one of the most beautiful on its way to a potential 30-50 ft. height and spread, although in gardens it more typically reaches only half that size. Its name is derived from bluish green leaves with shallow, rounded lobes that create a distinctive sight from a distance. This species is well-suited to hot, dry areas and tolerates poor soils. It is host to many favorite butterflies, including California sister, mournful duskywing, golden hairstreak, as well as numerous other insects.
Quercus kelloggii—black oak. Few oak species compare to the four-season beauty of black oak. Spring foliage unfolds in shades of salmon and rose, leading to shiny, bristle-tipped, sharp-pointed, glossy green leaves in summer; autumn gold rivals eastern deciduous foliage, and deeply furrowed black bark is a stand-out in winter. Completely drought-tolerant, black oak grows slowly to 30-70 ft. and nearly as wide after great age. This long-lived tree supports birds and numerous butterflies.
Trees for Special Sites
The trees listed below are common and valued in their native North Bay habitats but can be problematic in a home landscape. Where there is adequate open space and a suitable environment, these trees will establish a notable presence. All host a variety of fauna.
Acer macrophyllum—big leaf maple. A deciduous, fast-growing, majestic tree 30-75 ft. tall and 30-50 ft. wide native to streams and moist canyons. Large leaves become golden yellow in autumn.
Acer negundo—box elder. A fast-growing, deciduous tree to 60 ft. high and wide native to riparian habitats, usually avoided in landscapes due to brittle wood, unwanted suckering, re-seeding, and hosting box elder bugs. Some varieties have fewer drawbacks; all have attractive mature growth with divided leaves.
Alnus rubra—red alder. A fast-growing, deciduous tree with gray bark and straight trunks to 90 ft. native near the coast in moist woodlands and stream sites. Cone-like fruits hang on trees in winter but countless winged seeds are dropped. Roots may be invasive.
Arbutus menzesii—madrone. A strikingly beautiful, drought-tolerant evergreen of variable height and width from 20 to 100 ft. Slow-growing, madrone is notoriously difficult to establish in gardens but deep green, leathery leaves, reddish fall fruits, and peeling mahogany bark create an architectural presence.
Fraxinus latifolia—Oregon ash. A deciduous, fast-growing tree 40-80 ft. tall and nearly as wide with long leaves divided into many leaflets. This ash is suited to poor soils with poor drainage and is tolerant of both standing water and summer drought. It is bothered by several pests and diseases and drops considerable litter from dense seed panicles, making it unsuitable for home landscapes.
Fremontodendron californica—western flannel bush. A shrubby, often short-lived evergreen to 20 ft. tall and half as wide with fuzzy, flannel-like foliage irritating to skin and eyes. Covered with 3-in. golden flowers spring-summer and completely drought tolerant, this fast-growing native with shallow roots requires pruning to establish tree form, careful siting out of wind and wet areas, and sufficient staking to protect from wind damage. It creates a stunning sight in full bloom.
Juglans hindsii—Northern California black walnut. A deciduous, drought-tolerant tree 30-60 ft. high and wide, often with multiple trunks. Foot-long leaves are divided into nearly 20 leaflets, each 3-5 in. in length. Long catkins dangle in spring; small, tasty nuts are enclosed in a fleshy husk in fall.
Pseudotsuga menzesii—douglas fir. Prominent and moderately fast-growing in coastal climates to more than 200 ft. with great age. Sheer size renders evergreen douglas fir impractical for residential use, but it is widely planted for use in the construction industry.
Quercus lobata—valley oak. Deciduous in winter when it tolerates wet soil in oak savannahs but requires dry conditions in summer with access to ground water in deep soils. Regal in stature, valley oak grows to great age and 100 ft. in height away from the coast, distinctive in parklike settings but too large and messy in landscapes.
Salix laevigata—red willow. Fast-growing, semi-deciduous to nearly 50 ft. in height and width, usually with multiple trunks. Not a tree for small gardens, it serves a key role near ponds and marshy sites where most other species will not tolerate poor drainage from nearly constant ground moisture. It supports a wide range of butterflies, birds, and bees attracted to pale yellow or red catkin blossoms in winter and spring; tufts of seeds are borne away by wind. It tolerates hard pruning, even to the ground.
Sequoia sempervirens—coast redwood. The signature evergreen of California, dominant along the fog belt of the North Coast where it reaches heights well over 300 ft. after many decades, if not centuries. Several varieties of uniform habit create picturesque groves when planted in wide, open areas but not in landscapes where shallow roots prohibit typical gardening practices. Year-round moisture and absence of competition with other trees promote steady growth, but trees cannot survive hot, dry sites.
Umbellularia californica—California bay. Leathery, aromatic foliage on 30-60 ft., often multi-stemmed trees. Clusters of tiny, yellow blossoms in spring lead to flesh-covered acorn-like fruits that promote unwanted self-seeding. Aphids commonly infect foliage and secrete honeydew that drops and promotes black sooty mold on leaves and other surfaces.