Trees in California Don’t California is home to the world’s tallest, largest, and oldest trees—coast redwoods, giant sequoias, and bristlecone pines. We also enjoy many beautiful landscaping trees imported from around the world. plant a Unfortunately, a few of the trees we use in landscaping can cause serious ecological damage by escaping our gardens pest! and spreading into California’s wildlands. These invasive trees can Give them an inch and push out native plants, they’ll take an acre... reduce wildlife habitat, impair water resources, increase erosion, create fire hazards, and degrade recreational opportunities. © 2002-2004 Steven J. Baskauf J. Baskauf © 2002-2004 Steven This brochure was Tree-of-Heaven (Ailanthus developed to help gardeners altissima), at one time a popular street tree, has spread along the and landscape designers coast and through the Sierra choose trees that work for foothills. It creates dense thickets their sites while protecting that reduce or eliminate native the health and beauty of vegetation and wildlife habitat. the California landscape. The brochure includes eighteen trees that should be avoided in gardens and landscaping in California. On the reverse side, it describes a few of the many non- invasive alternatives that can be planted in place of invasive trees. Your local nursery may also suggest alternatives best suited to your location. The invasive trees in this brochure fall into two categories. Those in the ‘Don’t Plant’ section are known to scientists to cause serious damage to wildlands in at least a portion of California and should not be planted in those areas. The trees under ‘Caution’ have been observed escaping into wildlands, Suggested alternatives for invasive but full scientific studies have not been completed on Trees in California the extent of their effects. Don’t Plant Don’t Plant Don’t Plant blue gum eucalyptus saltcedar Brazilian peppertree Eucalyptus Tamarix species Schinus terebinthifolius globulus A serious riparian invader A serious problem in southern Found along the throughout California and California. Less of a problem in coast from Humboldt southwestern states. Uses the San Francisco Bay area and to San Diego and in excessive amounts of water, Central Valley, but caution the Central Valley. salinates soil, changes should be used if planting Most invasive in water courses, diminishes near wildlands. Creates dense coastal locations. wildlife habitat, and stands which shade out other Easily invades native increases fire hazard. Not vegetation within a few years B. Richardson plant communities, commonly sold, but still of introduction. causing declines occasionally available. © 2003 Michael Charters © 2003 Michael in native plant and B. Richardson animal populations. Extremely flammable. scarlet wisteria Chinese tallow tree Russian olive Sesbania punicea Elaeagnus angustifolia Sapium sebiferum New to California, spreading A huge problem in southern Found throughout California. along the American River states, this species has Able to spread long distances in central California. Also recently been found in with the help of birds and found in the Delta and California wildlands. Grows mammals. Invades river and northern California. A serious and spreads rapidly, pushing stream corridors, pushing problem in South Africa and out native plants. out native willows and Florida. Grows and spreads cottonwoods. Reduces water rapidly along river and stream levels. Provides poor wildlife corridors, pushing out native habitat. Serious invader in myoporum © 1998 John Randall, PhD. © 1998 John B. Richardson vegetation and wildlife. Seeds other western states. Myoporum laetum PLANTS Database © Larry Allain @ USDA-NRCS Invades along the coast from Sonoma County to San Diego. Forms dense stands with no other vegetation. Can Mexican fan palm cover large areas. Washingtonia robusta Spread by birds. Melaleuca quinquenervia, the Australian Leaves and fruits A problem in southern paperbark tree, was introduced to Florida are toxic to wild- California, where this palm from Australia for landscaping purposes. life and livestock. can be prolific. Crowds out Today the tree covers more than 450,000 Burns easily. native species in wetlands, acres of south Florida natural areas, and Doesn’t typically canyons, and coastal lagoons. is one of the biggest threats to the Florida spread in interior areas. Everglades. © 2002 Tony Morosco Tony © 2002 Forest & Kim Starr, USGS & Kim Starr, Forest Caution Caution Caution The trees in the Caution section have been acacia olive observed escaping into California wildlands, but Acacia decurrens, A. dealbata, and Olea europaea A. melanoxylon it remains unclear whether they cause serious Produces hundreds of seeds damage. You may want to avoid them if your Acacias grow along most of which are spread by birds property is located near natural areas. the coast and inland in the and mammals. Creates dense central portion of the state. canopies that shade out California peppertree They spread by seed, root other vegetation. Though Schinus molle suckers, and stump sprouts, commonly grown as a crop in forming dense stands. California, gardeners should Also called Peruvian peppertree, use caution planting this tree B. Richardson this South American plant is not near open space. native to California, despite its common name. Found in southern California, Sierra Foothills, and DiTomaso © 2000 Joe A. decurrens edible fig the Central Valley. Seeds spread Ficus carica by birds. Invasive in stream and riverside habitat. Can be a problem in the © 1999 John Randall, PhD. © 1999 John San Francisco Bay area, the Central Valley, and southern California. black locust May be spread by birds Robinia pseudoacacia and deer, as well as by © 2000 Joe DiTomaso © 2000 Joe vegetation fragments. Widespread in northern B. Richardson Can dominate stream A. dealbata A. melanoxylon California, including Tahoe and riverside habitat. B. Richardson National Forest, although mostly present in small patches. Spreads by seeds and root sprouts. Seeds, leaves, single seed hawthorn Crataegus monogyna and bark are toxic to humans mayten B. Richardson and wildlife. Maytenus boaria An established invader in the Pacific Northwest, Has escaped gardens in the now spreading through Canary Island date palm Davis area (Central Valley). More northern California. Phoenix canariensis information is being gathered Capable of long-range about potential ecological Can spread quickly in seed dispersal by birds. damage this tree may cause. southern California Creates dense thickets, wetlands and riverside changing the structure of habitats. Seeds spread by woodland understories. DiTomaso © 2000 Joe birds. May hybridize with and threaten native hawthorn B. Richardson species. Courtesy NZ Palm www.nzpalm.co.nz Courtesy NZ Palm Non-Invasive Alternatives Good Alternatives Good Alternatives There are hundreds of beautiful, functional trees Arranged roughly from smallest to largest... bronze loquat that do not pose an ecological threat to California’s Eriobotrya deflexa wildlands. This brochure recommends only a selection of the trees that can be planted in place of hybrid crape myrtle Fast growing and easily trained. New leaves emerge the invasive trees on the opposite panels. Consult Lagerstromeia hybrids bright copper before turning green. Bunches of creamy your local nursery or Master Gardener for additonal Stunning tree, great in a hot area. Showy summer flowers white flowers in spring. Easy to plant and care for. information on choosing the right tree for your site. in hot pink, white, lavender, and other colors typically Requires well-drained give way to brilliant fall foliage. soil. Can be subject to Native alternatives Somewhat susceptible to aphids. fireblight. California native trees are not found for sale as often Not the best choice for coastal Evergreen as non-native trees. However, where conditions are locations. Zones: 8-24 appropriate, the right native tree can be a good choice— Deciduous Height: 12-30 feet particularly those grown from locally occurring stock. Zones: Varies by hybrid Width: 15-30 feet Redwoods, coast live oak, and Height: www.worldplants.com Symbols Used: 8 to 25 feet, varies California buckeye can often by hybrid. be obtained at native plant Full sun sweet michelia © Monrovia sales held by chapters of the Part shade Michelia doltsopa Full shade California Native Plant Society. Prune to create a narrow, upright tree. Furry brown buds Drought tolerant open to cream or white Low water Chinese fringe tree Non-native alternatives blossoms. Thin, leathery, Many non-native trees are Moderate water Chionanthus retusus dark green leaves are red “wildland-safe” because they Regular water Blooms like clouds of the whitest, feathery flowers. underneath. cannot survive and reproduce High water Handsome bark provides winter interest. Will grow in in the wild without human Zones noted from most central California Evergreen care. However, much remains Sunset Western environments. The olive-like Zones: 15-24 unknown about the ability of Garden Book fruits can be a litter problem. Height: To 25 feet plants to become invasive over May produce a significant Inc. Nursery, Bay Monterey Miller, Luen time. Care has been taken to ensure that none of the amount of pollen. recommended non-natives is invasive, but it is possible that some of these trees may become pests in the future. Deciduous eastern redbud If you see one of the recommended alternatives growing Zones: 3-9, 14-24 Arboretum Courtesy Salisbury University