A bit of Web searching turned up a provisional list of woody plants not susceptible to crown gall. (The word "provisional" is to protect the innocent.) The following plants are not known to be hosts of the disease, according to information from Cornell University (http://pmep.cce.cornell.edu/recommends/treerecommends-lib/crown.gall.dis.tree96.html): barberry, hornbeam, true cedars, ginkgo, golden-rain tree, tuliptree, mahonia, spruce, linden, boxwood, catalpa, beech, holly, larch, magnolia, black gum, pine, Douglas-fir, bald cypress, and hemlock. A list from Auburn University (http://www.acesag.auburn. edu/department/ipm/cgo.htm) adds birch, firethorn, redbud, smoke tree, and sweetgum. Of course, no one can guarantee that crown gall will never occur on these plants, but it is a starting point.

A list of plants with resistance to crown gall also appears in Plant Health Care for Woody Ornamentals, a publication developed by authors at several institutions and funded by the International Society of Arboriculture. In addition to the plants mentioned above, the list in this publication adds deutzia, serviceberry, yellowwood, yew, and Zelkova.