Ulmus minor English elm
Decades ago, large old avenues of English elm extended from the Bookstore in the direction of Salvatierra Street, Mayfield Avenue, and Alvarado Row. They are distinguishable from the closely related American elm (U. americana) by corky ridges on branchlets or on the numerous suckers that can generally be found springing from the extensive root systems. Suckers are particularly vigorous after root damage caused by trenching or building construction, and can be seen forming thickets in hedges and shrubby places. U. minor (also known as U. procera) is widely distributed throughout Europe; the name English elm is mainly confined to the United States. The common elm in England is the small-leaved elm U. campestris.
In the spring, before the leaves appear, tiny flowers form and from them spring bunches of bright green fruit consisting of ½ -inch disks with a seed at the center. The bright green clusters, which may be mistaken for leaves, add a very delicate color to flower arrangements. When ripe, the fruit will be a papery brown samara and will blow about in conspicuous drifts. A child’s pastime is to take a mature leaf and scratch out alternate stripes between the ribs using the fingernail, to leave a decorative pattern.
Both English and American elms are subject to Dutch elm disease, which has spread across the United States from the East and which is due to a fungus that is spread by bark beetles. Resistant strains have been under development for many years, but meanwhile the plantings in many cities are doomed. The small-leaf Chinese and Siberian elms and the zelkovas are resistant. According to a 1975 count by D.S. Schroder, there were 146 small-leaf elms and 533 English elms on campus.
In early 1977, 183 trees with Dutch elm disease were cut down on campus at a cost of $15,000, paid by the State of California. Not all the elms were taken down; walk down Salvatierra Street as far as 627; see one at the north wall of 505 Lasuen Mall. Two large ones at Columbae, 549 Lasuen, were removed November 2004. In 1985 the elms of San Jose were attacked, especially those along South 7th Street near San Jose State University. After consuming the foliage, large numbers of yellow and black caterpillars were falling from the trees and heading off to find good places to pupate. According to the California Department of Forestry, there were over 24,500 elms in Santa Clara County in 1985. At a cost of $1500 to remove a single tree, or $100 to dose a tree with pesticide, this outbreak was not a trivial matter (San Jose Mercury News, August 22, 1985).
Diseased elms should be buried, but homeowners wishing to store firewood should know that the beetles are attracted to the potential new breeding site by smelling the saw cuts. The wood should be stacked on rails, covered with 6-mil clear (not black) plastic down to the ground and for 1 foot outward, and sealed in by dirt shoveled onto the surround. This hides the wood’s odor. Larvae that are already inside will be foiled by the rapid drying of the cambium layer that they need to feed on. The few beetles that may emerge will be contained by the plastic. This procedure, known in the trade as tarping, is recommended also for eucalyptus firewood containing, or hospitable to, longicorn beetle larvae.
Illustrations: Jasper Ridge plant photo archive
Name derivation: Ulmus – classical Latin name for the elm.
About this Entry: The main text of this entry is from the book Trees of Stanford and Environs, by Ronald Bracewell, published 2005. John Rawlings noted the 549 Lasuen removals c. 2005. Minor edits Oct 2019 (SP).