Coefficient of Conservatism:
Coefficient of Wetness:
AMERICAN ELM, WHITE ELM
R. W. Smith
Characteristic of swamps, such as river floodplains, even cedar swamps, often with Silver Maple, and also in rich upland hardwoods; also an important early successional species.
Occasional plants, especially on young sprouts, produce leaves as harshly scabrous above as in U. rubra, feeling like coarse sandpaper, but the leaves are more likely to be smooth beneath. Both this species and U. rubra have a familiar and characteristic “vase-shape,” whereas in U. thomasii the trunk generally extends straight into the crown before forking. The outer bark of this species consists of alternating pale and dark brown layers, while in U. rubra the outer bark is solid brown.
Our stately elms have suffered especially from the Dutch elm disease, first noted in Michigan in 1950 near Detroit, Wayne Co., and subsequently fatal to most trees essentially throughout the state; the disease is caused by an ascomycetous fungus, Ceratocystis ulmi, spores of which are carried by beetles and enter healthy tissue via wounds caused by feeding of the beetles on young shoots. While elms are still abundant, they typically die as small trees, the species now essentially converted to a scruffy, early successional species of old fields. It is particularly poignant that younger naturalists will have no memory, only a few old pictures, of the giant elms with wide-spreading, arching crowns that made floodplain forests natural cathedrals.