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Garden Doctor: How to keep an old olive tree alive

By From page A7 | October 14, 2012

Coming up

* Fall gardening workshops and plant sale: 9 a.m.-noon Saturday, Oct. 20, Woodland Community College, 2300 E. Gibson Road. Free classes on bee-friendly gardening, edible landscaping and backyard and worm composting

* Davis Fall Festival: 8 a.m.-1 p.m. Saturday, Oct. 27, Central Park, Third and C streets. Plant sales, exhibits, fun for all ages

* Pumpkin Smash and Bash: 6-9 p.m. Saturday, Oct. 27, Heidrick Ag History Center, 1962 Hays Lane, Woodland. Visit www.aghistory.org for details

Question: We transplanted an olive tree from our old house five years ago and it seems to be doing surprisingly well. We water it almost daily for about 20 minutes. I notice that it has some dead branches, and also something that looks like “sawdust” from the tree on the branches and ground. What should we do to keep this nice old tree alive?

Answer: Olea europaea are evergreen trees that thrive in our hot, dry summers because they originally came from the Mediterranean region. They need full sun, and look best when grown in deep, rich soil, but will also grow in shallow, alkaline or stony soil and with little fertilizer. Olive trees are deer- and wind-resistant and often the mature trees have an interesting, gnarled trunk and branch pattern.

There are fruiting and fruitless varieties, although most fruitless trees occasionally will bear fruit. Young trees gain height rapidly but continued growth slows considerably, eventually reaching 25 to 30 feet.

You should cut back on the watering, especially with cooler weather and winter rains coming. Dead branches can be pruned at any time. The “sawdust” sighting is a sign of carpenter bees. Looking similar to bumble bees and often larger in size, female carpenter bees bore into wood, especially dead wood, to make nests, depositing food (pollen) and a single egg. Pruning back dead wood should prevent a majority of the problem. For the most part, the bees are considered beneficial because they are excellent pollinators.

Question: How do I get rid of stink bugs? I have found them in and around my house.

Answer: Stink bugs are not new to the California home gardener and have been discussed in articles dating back to 1952. There are several varieties of stink bug and it is important that you identify which one you have. Visit www.ipm.ucdavis.edu/pmg/garden/veges/pests/id/idstinkbug.html to pinpoint your particular pest. The brown marmorated stink bug, Halyomorpha halys, a newcomer that arrived in the United States from Asia in the 1990s, is a pest of agricultural crops in many states.

As their common name suggests, all share the ability to stink when disturbed, a most annoying behavior. Stink bugs seek shelter as the days become colder. They congregate in large numbers on outside walls and will invade homes through small cracks. In the garden they will seek shelter under boards in refuse piles, weedy areas and in areas where they won’t be disturbed. Preventive measures would start with cleaning up such areas.

Examine the exterior of house to prevent them from coming inside. When found inside, vacuum furniture and then dispose of the bag.

Hand picking these bugs and their eggs is another effective control method. The eggs will be white to pale green and are laid on the underside of leaves in clusters of 20 to 30.

The bugs are spread easily because they are hitchhikers. They have been found in vehicles and in furniture where they are undisturbed. Both the adult and nymphs suck juices from fruits and seeds. Their sucking creates pockmarks and damages the flesh, making it pithy, brown or corky. Their appetites include tomatoes, legumes, pears, stone fruits, citrus, grapes, berries, fig and vegetables, as well as shade trees.

Speaking of bugs in general, fall is a good time to clean up your garden. Prevention is usually the best practice. Weed at least one more time to eliminate potential sites for overwintering insects, snails and slugs, and to reduce spring weeding. Take out dead and spent annuals. If you have a large bare area for next year’s garden, think about planting a cover crop. Have fun as you think about and plan next year’s garden.

Question: I saw a cool plant on Putah Creek by Old Davis Road.  It is a large shrub with white trumpet flowers (three to four inches long), purplish stems, and lobed fuzzy leaves. Is it a native? Can I put it in my garden? 

Answer: You and the Garden Doctor must enjoy walking in the same area. There are several impressive examples of this plant growing near the east end of Putah Creek, near the parking lot at Davis Commons. What you are probably seeing is commonly called Jimson weed, datura or devil’s claw, and is native to Mexico. It is very poisonous, so be careful in handling it.

Many domestic varieties are available, some at local garden centers, that would do better in the home garden (although probably also toxic). You can look for these plants with the name Brugmansia. They are tender perennials, and may freeze completely but are likely to grow back. Slugs and snails seem to enjoy eating them, without fatal consequences.

— Send questions, addressed to the “Garden Doctor,” by email to [email protected], voice mail to 530-666-8737 or regular mail to UCCE Master Gardeners, 70 Cottonwood St., Woodland, CA 95695. Be sure to include your contact information, because any questions not answered in the Garden Doctor column will be answered with a phone call or email to you. You can request the Yolo Gardener newsletter delivered by email and learn more about the Master Gardener program in Yolo County at http://ceyolo.ucdavis.edu/Gardening_and_Master_Gardening

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