As gardeners branch out, growing more and more of their own food, their thoughts often turn to those expensive jars of olives and bottles of olive oil, and how it would be great to produce their own. Jim DeFrisco, Contra Costa Master Gardener, has discovered his own passion for processing the olives from his 15 trees.
DeFrisco, who spoke about olives at the Our Garden class, says it takes work to prune trees, harvest the olives and then turn them into delicious fruit and oil, but it's well worth it. Here are his tips on growing and processing olives.
Although there is a growing interest in olives in California, the state is not a player on the market. Less than 1 percent of the world's olive crop is grown in the state. Three Mediterranean countries produce 95 percent of all the olives and olive oil sold in the world; 60 percent come from Spain. California has the perfect climate for growing olives, however.
Brined olives and Extra Virgin Olive Oil from a backyard grove of olive trees.
Making choices When deciding what variety of olives to plant, consider how you want to use the fruit -- for brining or pressing. Do you even want fruit or do you just like the beauty of the tree? Some varieties are better for brined production while others produce more oil. However, DeFrisco says, you can brine or press any variety of olives. Fruitless varieties include the Majestic Beauty, a full-sized tree, and the Little Ollie, a dwarf tree. For oil production, consider the Frantoio, Arbequina or Leccino. For table olives, popular varieties are Picholine, Manzanilla, Mission and Sevillano.
Planting, pruning Plant in fall or spring. Olive trees are drought tolerant. They need well-draining soil, but don't have high nutrient requirements. Prune trees in the late spring and early summer. Keep trees small to facilitate harvesting. Olives are alternate bearing trees, meaning that one year they have a bumper crop and the next year they don't produce well. To help even out the harvest, do a hard prune during the bumper crop year, reducing the yield and ensuring that the "off" year has more yield.
The olive fruit fly is a serious threat to olives. The female lays one egg in each olive, and can lay up to 40 eggs a day. The eggs hatch and the larva eat the olive from the inside. Gardeners have been reporting total losses on their trees. The damage is more prevalent in the cooler climates in the Bay Area. For the larvae to develop, temperatures must range from 68 to 85 degrees. When temperatures climb to 95 or above, the larvae don't progress. Good sanitation is key to controlling the fly. You can use traps to determine if you have an infestation, and to control it. You also can find sprays that are effective in killing the flies.
Table olives can be processed different ways. Lye-cured is the fastest method, but it produces the blandest olives. They are the least bitter of all, however, and you can add in additional flavor, such as garlic or red peppers. After processing, they can be canned through pressure canning. Water-curing takes 6 to 8 weeks and produces a more bitter olive than other methods. Olives need to be cracked or cut before being submerged, and water has to be changed daily. Dry salt-cured is relatively fast, taking 5 to 6 weeks. Olives processed this way are more bitter, soft and shriveled. Olives can be stored in the refrigerator for six months or frozen for longer storage. Brine-cured is the slowest method, taking 3 to 6 months, but it produces the tastiest olives. Brine, made from a cup of kosher salt to a gallon of water, needs to be changed once a week. In this method you are fermenting the olives, much as you do when making pickles or sauerkraut. These olives can be stored in brine for up to a year.
Making olive oil
Unless you want to invest in a commercial mill, you'll do well to have your olives pressed at a production company that offers "community days" or an entrepreneur who is providing the service.
The olives, seeds and all, are ground into a thick paste. The paste is then put through a 45-minute mixing process where some of the oil starts to separate out. The mixture is then run through a centrifuge where the oil is extracted.
In community presses, all the olives are mixed together and you receive a portion of oil commensurate with the pounds of olives you brought in. With a private miller, your olives are processed separately and the end product is exclusively from your olives.
You can expect to pay milling fees per pound or by hour for the service.
About Our Garden
Free gardening classes are offered 10-11 a.m. on Wednesdays at the garden, Wiget Lane and Shadelands Drive in Walnut Creek. Master Gardeners are available to answer questions at the Help Desk; plants, seeds and worm compost also are available for sale.
Next time: "Pesticides -- What to spray and what not to spray," with Doug Freier.