Weekly Express-News Article
Saturday, February 25, 2006
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
“Not So Evergreen” 

            The live oak leaves are falling.  It is a normal thing for them to lose their leaves this time of the year.  Instead of evergreen we should probably call them “mostly evergreen.”  Within two weeks they will releaf.  The caterpillars love the new live oak leaves so expect three varieties to appear for a short time to feast on the young leaves.  The most noticeable will be the spring canker worms and oak leaf rollers.  They hang from web strings and are unpleasant as you try to enjoy the spring landscape.  No need to kill the caterpillars, they have been feeding on live oaks for eons without any long term impact on tree health.

            Another thing you will notice when the leaves fall is the ball moss.  Its favorite environment is the branches deep in and under the crown where there is little growth and high humidity.  The ball moss is not hurting the trees, it is not a parasite.  Ball moss is an epiphyte; it draws moisture and nutrients from the air.  The plant will even grow on fence lines or utility wires.  There is no need to kill it, unless you do not like its looks.  Tree care companies apply Kocide (copper hydroxide) to kill ball moss.  Baking soda also works. 

There has been some discussion of the live oak leaf fall in relation to the drought.  The lack of water this year may have speeded up the drop for some trees, but as far as I know there is no documented evidence.  Every live oak is an individual grown from seed, and they all have different characteristics.  Two trees next to each other may drop their leaves at different times one year and at the same time the next year. 

            The most important thing about leaf drop is the leaves, live oak leaves are valuable.  They can be used for compost and mulch.  They never should be bagged for the garbage collection. 

            The easiest way to benefit from live oak leaves is to let them decompose on the lawn.  The leaves release nitrogen and other nutrients through the process.  If neatness is your “thing” and years of leaf raking training makes it impossible to let the leaves decompose naturally, mow them into small pieces.  Within a few weeks the material will disappear completely.

            The leaves can also be used for raw material in the compost pile.  Raking leaves is good exercise and a wonderful “daydream” job.  You know what a “daydream” job is?  You think about South Seas islands, heroic sports performances, or beautiful (handsome) movie stars. 

            My favorite use for live oak leaves, however, is as mulch.  The leaves are sturdy and small so they can be spread easily and do not crumble or decompose too quickly.  Three inches deep around the tomato plants helps reduce the likelihood of blossom end rot.  In the rows between flowers or vegetables they make a good walking path and reduce weed growth plus conserve water. 

            Three to four inches deep over the root system on newly planted trees and shrubs will contribute to increased growth rate and make it unnecessary to string mow close to the trunk and stems.  Mark Petersen, our urban forester, has said that string mowers are a tree’s worst enemy.

            If you absolutely must bag your leaves, alert the gardeners in your neighborhood.  Most can use more leaves.  They will pick up the bags if they have time