Signs of Tree Trouble

Sometimes it takes only a few months, sometimes it takes two or three years, but unfortunately many of us will have native trees on our lot die. Usually it is from environmental damage during the building process from two trauma: ditching for utlility hookups (and sprinklers) and compaction/burying of roots. Post oaks are most sensitive to disturbance and may take up to five years to go. (I've lost seven in four years). Live oaks are more tolerant and cedar elms seem to be almost indestructible. Remember that here in our shallow soil, 80%-90% of the roots are in the first foot of soil. Ours don't have "tap roots" as do trees back east (except for mesquite, and that is another story).

What can you do? First and foremost is "look for the shoulders - or flare". Where a tree emerges from the natural level of the ground its trunk is thicker, it has a spread or flare. If you look at your trees and they go straight into the ground you know they have been buried. A post oak can stand about two inches of overburden; more than that, compounded by compression of the soil by heavy machinery, causes the roots to have trouble getting both water and oxygen. Yes, roots need oxygen. This will cause stress to the tree, which is often manifested by it putting out small new branches on the lower main trunk. If unrelieved, this choking of the roots will either kill it or make it more susceptible to attack of the vascular system by fungi of several sorts - which will eventually kill it.

If you have these trauma you can mitigate their effects in several ways:

• One is to restore the natural soil level. Dig away the added soil around the tree at least two feet out from the trunk to the natural soil level. You can mulch over this area but add no more than two or three inches of mulch per year.
• Secondly, fertilize - but not too much. Nutrition is not the problem, but some help will assist the tree.
• Thirdly - AND MOST IMPORTANTLY DURING THE DROUGHT- is to water THE TREE not just your yard. A St. Augustine lawn requires about an inch of water a week - PROPERLY APPLIED. Properly applied means watering to a depth of 6 inches - difficult to do with our percolation rate (time to soak in) of .6 (yes - six tenths) of an inch per hour. But since the tree roots are six to eighteen inches down, watering the lawn doesn't water the tree. The lawn soaks up most of it. Actually most of it runs off because most people water too long at a time (i.e. 30 minutes). Watering the tree means "soaking" - using a soaker hose for HOURS or a garden hose at just a trickle (remember, more will only run off) for several hours at several points around the drip line of the tree. This only needs to be done every couple of weeks during drought, but it will definitely help the tree overcome the compounding effect of the man-induced stresses.