Experts tackle readers’ garden questions.
Q: We live in Newcastle, about 800 feet elevation. We have a few valley oaks and digger pines, but mostly live oaks. Many look dead. Is this because of the drought?
Judy James, Newcastle
Master gardener Dennis Appleby: Interior live oaks are slow growing. Young trees tend to be sparse and angular, but with time develop a low-branching, full, round canopy. The tree is evergreen with leathery oval or elliptically shaped leaves 1 to 3 inches long, dark green above and yellow-green below.
Valley oak is reputed to be the world’s tallest and most massive oak. It is deciduous, losing its leaves in winter. With pale undersides, its matte green leaves are 2 to 4 inches long and 1 1/2 to 3 inches wide with seven to 11 deep lobes.
Although California native oaks are well recognized for tolerating extended periods without rainfall or irrigation, they do incur “water deficits” and can be injured. Water deficit injury can range from a small reduction in growth rate to death of a whole tree.
The level of injury depends on the severity and duration of the deficit. Common symptoms include wilt in young seedlings or young shoots; reduction in growth rate; early fall color and early leaf drop; tip dieback; branch dieback; and whole tree death.
Water deficit affects trees differently. Interior live oaks typically hold most of their leaves during periods of drought, while valley oaks may completely defoliate.
The first thing to do is determine if any or all of the suspect trees are in fact dead. Without being able to see the trees, determining their viability is very difficult. We would recommend using the services of a certified arborist to help make this determination. They would be able to check each tree and tell you if they have a possibility of recovery.
According to the U.S. Department of Agriculture Forest Service, residents in Gold County counties have noticed in recent years a significant decline of foothill pine, also known as digger pine.
Symptoms include branch dieback, partial crown fade or whole tree mortality. While these are typical symptoms of tree decline, they are not diagnostic of any one causal agent. Recently, the numerous and rapid loss of trees has been startling and cause for concern.
For additional information in your area, you also may want to contact the Placer County Cooperative Extension Office, 11477 E Ave., Auburn; phone 530-889-7385.
Dennis Appleby is a UC Cooperative Extension master gardener for Sacramento County.
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