John Britton Tree Service
P.O. Box 424
St. Helena, CA 94574
(707) 963-7578
The trees surveyed in this analysis represent a cross-section of approximately 30% of the total population of publicly-owned elms are mature, having been planted near the turn of the century. The trees are large, providing a significant proportion of the foliar canopy arching over and shading Berkeley streets.
Berkeley now faces difficult decisions regarding the trees. Many of the elms pose potential hazards, some serious enough to require relatively removal. Others will be expensive to maintain in a relatively "safe" condition. Yet the removal of the trees will constitute a significant loss to the city in terms of temperature amelioration, property values, pollution absorption, and aesthetics.
The elm trees have suffered from a continual effort to keep them confined to their "allotted" growing space. The trees' canopies have been repeatedly cut back or "topped" about every ten years. This practice leads to decay and weak limb structure. Roots have also been severed for sidewalk installation, and have been cut back further as the trees continue to grow over and under the concrete, causing significant disruption to the sidewalks and curbs that create tripping hazards for pedestrians. The practice of routing out main buttress roots during sidewalk repair has created extensive decay in the lower trunk of many trees. These practices need to be re-evaluated, and changed if the city is to have a long term management goal of maintaining large trees to shade Berkeley streets. We have included herein Tree Work Specification, and suggested methods of root pruning that we believe will enhance tree structure, prolong a tree's useful life, and improve public safety.
The presence of Dutch Elm Disease (Ceratocystis ulmi) in Berkeley is a concern since tree management may be futile if the disease becomes epidemic. In 1990 there were eight trees positively identified with Dutch Elm Disease (DED), less than 1% of the 1000 publicly owned elms in Berkeley. Proper sanitation of trees is extremely important to keep the disease at these low levels.
We recommend that the elm trees in Berkeley be scheduled for replacement over a long period of time, as they become extensively decayed or unstable. The results of our investigation show that although there are problems in most trees, extensive problems are found only in about 10% of the trees. The rest should be monitored regularly, and scheduled for pruning every five to seven years. The remaining unsurveyed trees should be evaluated and added to this elm tree maintenance program. If the trees are no longer severely topped, most can be expected to survive safely for another 20 to 40, or more, years.
We further recommend that as the trees are removed, the be replaced with relatively tall trees that provide large canopies over any street where space allows. As long as the trees are regularly maintained, they will not become unsafe due to size alone. Where high voltage lines are found, or other architectural features interfere with large canopies, smaller replacement tree species should be used.
Tree work recommended in this report is estimated to cost approximately $400,000. This averages about $80,000 per year. Since these trees represent approximately 30% of the total population of elms, the annual budget recommendation for pruning and caring for elms in Berkeley is $250,000. This maintenance cost should be viewed in relation to tree value. One large elms tree (38" DBH) in good vigor, with some minor structural problems is valued at approximately $15,000. Total tree value resulting from the Berkeley elms is therefore approximately $15,000,000.
This is page 15 of the document Analysis of the Condition of Elm
Trees in the Parking Strips in the City of Berkeley," February,
1991. This is an extensive study of Berkeley's Elms by arborist John Britton
of St. Helena, CA.
The presence of Dutch Elm Disease (Ceratocystis ulmi) in Berkeley is a concern since tree management may be futile if the disease becomes epidemic. In 1990 there were eight trees positively identified with Dutch Elm Disease (DED). This constitutes less than 1% of the 1000 publicly owned elms in Berkeley. We therefore believe that Dutch Elm Disease can be considered a relatively minor problem at this time. Were the trees allowed to reproduce naturally, or to be re-planted, such a percentage would be, indeed, insignificant. There are indications that the incidence of the disease may be increasing, but the trees are withstanding its affects nevertheless.
Proper sanitation is extremely important in the management of this disease. Sanitation requires removal of dead branches on a regular basis, as well as pruning to reduce the chance of limb breakage during the growing season.
California Department of Forestry (CDF) personnel are also concerned that unsterilized tools used to cut back trees under high voltage lines may be spreading the disease in the tops of the trees. However, fresh cuts made during the growing season in the tops of the trees attract disease carrying adult beetles that feed in the tops, and may spread the disease to several trees in one area. This seems a more likely scenario than spreading the disease on pruning tools. We highly recommend that pruning of elms not take place during the active season of flight by the European Elm Bark Beetle. CDF regulations restrict pruning of Elms from April through October, and require sterilization of tools between diseased trees.