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If you are a home gardener in Napa Valley, you can successfully grow olive trees. Olives are one of the most popular trees in the valley, and with a few pointers extrapolated from University of California research and other sources, you can enjoy their beauty in your own landscape.

Olive trees are evergreen and both ornamental and edible. They are relatively easy to grow and maintain, suitable for the fairly arid Mediterranean-type climate of the Napa Valley. They are not fussy about fertilizer, needing only nitrogen. Nor are they water hogs. Once established, they take to xeriscaping or even no watering at all, cutting down on irrigation chores.

The olive tree’s silver foliage, smallish, oblong leaves and graceful branches add interest to any landscape, large or small, including container gardens.

But olive trees are not without drawbacks. For one, growing your own olives for pressing or curing may cost more than you expected. In all likelihood, your olive oil or cured olives will cost you more than store-bought olive oil or olives and take more care and time than you imagined. Nonetheless, you may decide that the experience and satisfaction of growing and producing healthful food of your own is worth the expense and the journey.

David Layland, a U. C. Master Gardener of Napa County and past president of the group, has had an experience with olives that is probably typical. He planted nine olive trees primarily for landscaping purposes. Fruit production was almost incidental. The laborious harvesting required the help of friends.

Layland encountered unexpected costs for cultivation, care and maintenance, including the unavoidable pest problems, most notably the olive fruit fly. Then there’s the inevitable reality that friends move or fade away over time. Still, he is happy to be taking the olive tree journey.

The nutritional virtues of extra-virgin olive oil, a heart-healthy monounsaturated oil and antioxidant, have been widely touted. But research hasn’t shown whether there is any discernible difference in the health benefits between local and imported oils. What is certain is that extra-virgin olive oil contains more antioxidant polyphenols than virgin olive oil and is a healthier choice.

For pressing or curing, available varieties for home gardeners include Mission, true Picholine (not Redding Picholine), Majestic Beauty and Manzanillo. Five-gallon plants provide a good head start, but one-gallon plants, if available, are considerably less expensive. The Kalamata variety is excellent for brining or salt-curing.

Fruitless varieties (Little Ollie, Wilsonii and Swan Hill) are better choices for those who are not interested in food production. Alternatively, you can minimize fruit formation by applying a plant-growth regulator (available at garden centers) or using a high-pressure hose during bloom. But these methods are not reliable, so fruitless varieties are a more sensible choice. Fruitless varieties also produce fewer allergens.

Full-size olive trees reach 25 to 30 feet in height and can be just as wide. They can take heavy pruning, but consider the available space before you plant. University of California research suggests that more space between the trees leads to better fruit production. Although 16 to 20 feet is recommended, such generous spacing may not be practical in a home orchard.

If you have limited space, consider a dwarf variety such as Skylark Dwarf, which tops out at about 16 feet. Another method for selecting a suitable variety is by tasting oil samples at farmers’ markets or retail stores.

Olive trees need about 200 hours of winter chill. Some require a pollenizer variety, such as Pendolino, for good fruit production.

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Fresh olives are too bitter to eat without curing, but they can be pressed for oil. If you don’t have enough olives to meet the minimum at a commercial pressing facility, such as Jacuzzi in Sonoma, you can combine your harvest with others to meet the minimum. The olives must show no sign of pest damage. For curing, follow the step-by-step instructions in UCANR Publication 8267 (“Olives: Safe Method for Home Pickling”). You can get a copy of this publication at the Master Gardener office (address below).

Napa Valley olive trees have suffered from infestations of the olive fruit fly, which damages the fruit. Trapping, seasonal spraying, good sanitation (picking up all fallen fruit) and biological controls are among the tactics growers employ. Research is ongoing and, in the meantime, Napa County home gardeners should contact the Master Gardeners office about the current recommended methods for fruit-fly control.

Free Tree Walk: U. C. Master Gardeners of Napa County will host a guided tree walk of Fuller Park, 560 Jefferson, in Napa, on Monday, July 10, from 10 a.m. to noon. Enjoy a fun, informational stroll through the park, learning about its history and 41 different trees on site. Wear comfortable shoes. Restrooms are available and handicap accessible. The book Trees to Know in Napa Valley will be available for $15 each (cash or check only).

To register, call 707-253-4221. Walk-ins are welcome, but you are guaranteed to receive a complimentary map and additional information if you register at least 48 hours in advance.

Workshop

U. C. Master Gardeners of Napa County will conduct a workshop on “Growing Olives” on Saturday, July 22, from 9:30 a.m. to 11:30 a.m., at Big Dog Ranch, 1020 Congress Valley Road, Napa. Got an olive tree? Want to grow one? Learn the details for each season’s necessary activity for a healthy and tasty harvest. Controlling olive pests is also on the agenda. Online registration (credit card only). Mail-in registration (check only or drop off cash payment).

Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information.

UC Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) answer gardening questions on Monday, Wednesday and Friday, 9 a.m. to noon, at the UC Cooperative Extension office, 1710 Soscol Ave., Suite 4, Napa, 707-253-4143.

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