Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa
Help Desk Client: My mature 40 foot redwood trees seem to be showing signs of stress from the continuing drought. While it gets just as much water from my garden irrigation as it did pre-drought, I now am noticing that various branches are showing needle die-back. Can you tell me what's wrong? Is it the drought or something else affecting the tree? And if it's something else, what is it and what should I be doing to correct it and bring back the trees to full health?
We have completed our research. The symptoms are consistent with the types of water stress we are seeing on redwoods in the central parts of the county where redwoods are not well-adapted. Under the microscope, there also appeared to be some fungus, but not the aggressive type that would cause a serious problem in your trees. More likely the fungus, in an opportunistic way, came into the needles that were already dying from the drought stress. No treatment is advised or necessary, other than good cultural care of the trees.
The best course of action is to follow the advice you received while visiting us last week: making sure that you water the trees out at the dripline and beyond during the warm, dry summer and fall months prior to the rainy season. Avoid watering near the trunk which can predispose the trees to rot. Redwood trees will compete with each other if planted closer that 7 feet apart, increasing their water needs. Water stressed trees should not be fertilized. As long as the needles are green and growing during the spring and summer, fertilizer is probably not needed.
Also, as noted above, during the drought, the MGCC Help Desk has fielded many questions and concerns about redwood trees. A previous blog responded to many of your and others' concerns, especially with advice on irrigation, at http://ccmg.ucanr.edu/HortCoCo/?blogpost=19256&blogasset=12496. Your perusal of the advice and recommendations should help you determine the necessary steps to make your redwood trees healthy again.
I hope that your trees will become healthier ithis spring after all this good rain we are having along with the possibility of supplemental irrigation over the non-rain periods. Please let us know if you have any more questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (JL)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: email@example.com, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).