Symbolic of the Sacramento Valley, oaks offer a lot to home landscapes, but they're not for every garden. Here are some pros and cons to consider, courtesy of the UC Davis Arboretum staff:
• Picturesque spreading branches add beauty to the garden. Mature trees increase property values.
• Many oaks are long-lived and drought tolerant, provide shade and require little maintenance.
• Contrary to popular belief, many oak species grow rapidly and tolerate normal garden irrigation. Most California native oaks prefer dry summer conditions.
• Oaks support native wildlife like jays, squirrels, insects and songbirds.
• Some oaks, such as valley oak, are resistant to Sudden Oak Death, a disease that is epidemic in coastal northern California but not now a problem in the Central Valley.
• Trees that are too big for the site can cause problems for home gardeners. Pruning large trees can be expensive, and spreading roots can lift sidewalks and damage foundations.
• Leaf litter and acorns can be messy.
• Evergreen oaks create deep shade that makes it hard to grow other plants.
• Native oaks and lawns are not compatible. Frequent irrigation can cause fungal diseases in some oaks.
• Deep-rooted seedlings can be a challenge to weed.
• Some oaks, such as coast live oak, are susceptible to Sudden Oak Death disease, particularly in coastal regions.
Oaks' needs vary according to their species. Most thrive with minimum care – a layer of mulch and deep, infrequent irrigation. These varieties in particular thrive in the Sacramento Valley and are immune to Sudden Oak Death:
• VALLEY OAK (Quercus lobata): Mighty deciduous oak of the Central Valley is upright and fast-growing when young. It grows to 50 to 70 feet tall with a spreading crown as it matures. Tolerates moderate irrigation, heat and alkaline soils.
• ENGLISH OAK (Quercus robur): Fairly fast-growing deciduous tree to 50 to 60 feet tall with a wide open canopy. There are also upright forms with narrow canopies. Tolerates occasional to frequent watering.
• SOUTHERN LIVE OAK (Quercus virginiana): Picturesque evergreen oak of the South, with wide, open canopy of glossy leaves. Grows moderately fast to 40 feet tall and wide. Tolerates irrigation or dry conditions.
• GAMBEL OAK (Quercus gambelii): Small, rugged oak to 30 feet tall, deciduous, adaptable to many soil types and moisture levels. Fast grower in rich soil. Can be multi-trunked.
WHAT TO PLANT UNDER OAKS Oak partners – plants that make themselves at home under trees' spreading branches – have to like shade. But is that dry shade or irrigated shade?
Oaks native to California and the Mediterranean basin prefer dry summer conditions with little irrigation – deep watering once or twice a month. Potential partner plants need to have the same water needs or gardeners risk harming the oak due to overwatering.
Some suggested oak partners for California natives: Snow berry (Symphoricarpos albus), hummingbird sage (Salvia soathacea), Canyon Snow Pacific iris (Iris douglasiana), California fescue (Festuca californica), deergrass (Muhlenbergia rigens), coral bells (Heuchera 'Rosada'), island alumroot (Heuchera maxima), evergreen currant (Ribes viburnifolium) and toyon (Heteromeles arbutifolia).
• "Oaks in the Urban Landscape: Selection, Care and Preservation" by Laurence Costello, Bruce Hagen and Katherine Jones (University of California Agriculture and Natural Resources Publication 3518; $55, 265 pages. This comprehensive new book is a wonderful guide for anyone serious about oaks, particularly in Northern California. Hundreds of native and imported oak species are profiled (including where to find examples in Sacramento, foothills and the Bay Area) with attention to their unique qualities and needs. From acorns to Sudden Oak Death, this book tackles the care and nurturing of trees – whether heritage oaks or newly planted – as well as diagnosis and treatment of potential problems. Preservation issues, such as the impact of urban development and ordinances to protect trees, also are explored. Illustrated with scores of color photos. Available online from http://anrcatalog.ucdavis.edu or call (800) 994-8849.
• Shields Grove, UC Davis arboretum: Visit the campus' 6-acre collection of oaks. In artistic fashion, new ceramic plaques offer insight into the names and history behind more than 80 species in the collection. With places to relax and picnic, the grove is open free daily, dawn to dusk, with free one-hour street parking on Garrod Drive. Visitor parking ($6) also available in Lots 54 and 55. For a map and more details, click on the arboretum's oak collection page at http://arboretum.ucdavis.edu/oak-collection.aspx or call (530) 752-4880.
• www.californiaoaks.org: An offshoot of the California Wildlife Foundation, this Oakland-based project is devoted to protecting California native oaks. The website features lots of information on care of native oaks as well as how to collect, store and plant acorns; special projects for kids; plus links to nurseries that offer oaks and arborists with oak expertise. California Oaks can also be reached by phone: (510) 763-0282.
• Sacramento Tree Foundation: This local resource knows its oaks, including acorn propagation and conservation. Click on www.sactree.org or call (916) 924-8733.
• Oak Conservation blog: University of California experts share their latest research and tackle current issues about oaks in risk. Read it at http://ucanr.org/blogs/OakCon.
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