TREES OF LOS ALTOS

tree book

The Environmental Commission published the book Trees of Los Altos. The book provides an overview and pictures of the many species of trees one can find throughout the community as well as the benefits they provide. The Los Altos community features a stunning tree canopy, which helps to promote better air quality, cooler summers, natural shade and less reliance on air conditioning. The trees throughout the community greatly contribute to the quality of life, which the book beautifully portrays. Trees of Los Altos is available for sale at the Los Altos History Museum, the Los Altos Chamber Commerce, Los Altos Community Foundation and Los Altos City Hall or you can purchase a book on line by emailing environmental@losaltosca.gov. The book is $12.00 plus tax.


TREE PROTECTION

Great efforts are taken to maintain the tree canopy throughout Los Altos. If you need to remove a tree or are uncertain about which trees are protected in the community, please review the City’s Tree Protection Ordinance.


CARING FOR OAK TREES

oak

Los Altos is blessed with a large number of very big old oak trees. Unfortunately, building, paving and landscaping near these trees can easily damage their root systems and hasten their demise. If you own one of these magnificent oaks, it is important to understand their water needs and their root systems. Oaks have a number of deep roots to support their huge size, but the bulk of the feeder roots, which take up moisture and nutrients, are located in the top 1-3 feet of soil and extend as much as 90 feet out beyond the drip line. These roots are adapted to being wet in cool weather and dry in warm weather. If the soil gets compacted or dug into, or if extra soil is added on top of the existing soil level, the roots become damaged and the tree cannot fight off infection or starvation.


HEALTHY OAKS

  • Do not water near mature oaks in the summer. Young oaks will need some water year round.
  • Plant only drought-tolerant California native shrubs and groundcovers within the root protection zone (RPZ), which is half as big as the area between the trunk and the drip line. Do not plant within 6 feet of the trunk. Limit the amount of digging you do in this area.
  • Do not put extra soil on top of the RPZ or compact the soil in any way.
  • Leave fallen leaf litter in place to act as a mulch.
  • Provide adequate drainage around the tree. Basements and swimming pools that are down slope from oaks can act as dams, leaving oak roots too wet.
  • Put all utilities in one trench, preferably bored 3 feet underground to avoid destroying feeder roots.
  • Use decking rather than paving near oaks.
  • Consult a certified arborist if the tree looks stressed or unhealthy or if you plan to do some home improvements that might impact it.
  • To prevent Sudden Oak Death Syndrome, don’t bring in plants that are possible carriers, don’t bring in fire wood from contaminated areas, and wash tires, boots and tools before leaving any contaminated areas.

COMMON DISEASES

There are three major diseases of which you should be aware. Two, crown rot and oak root fungus, are most often caused by frequent summer watering or damage to the tree’s roots. Symptoms include yellowing and thinning of leaves, dieback of twigs, and general malaise. Crown rot also causes oozing of dark colored fluid from lesions in the bark. Oak root fungus is characterized by white filaments in the soil and mushrooms.

The third disease is Sudden Oak Death syndrome caused by the Phytophthora pathogen, a problem in north/central California. It is characterized by dark red to tar-black thick sap oozing on the bark surface. This bleeding is typically found between the root crown (the area where the trunk fans out to the roots) and a height of 6 feet. If your tree develops any of these symptoms, consult an arborist immediately. Sometimes the tree can be saved. Tanoaks and Coast live oak are particularly susceptible but more than 100 kinds of trees and plants carry the disease.

For more information see the website of the California Oak Foundation.

For more information about Sudden Oak Death Syndrome see the excellent website of the California Oak Mortality Task Force.