LOW TEMPERATURE INJURY TO ROOTS OF WHITE ELM

White elms (Ulmus americana L.) failed to leaf properly at Saskatoon, Saskatchewan, in the spring of 1950 following unusually cold weather in January. Although precipitation in 1949 and the first six months of 1950 was well above average, the symptoms were characteristic of moisture deficiency. Trees on cultivated ground and trees whose growth rate was below average suffered most. On the basis of symptoms, climatic records, and ecological conditions it is concluded that the above-ground symptoms were a result of the killing of roots by unusually low winter temperatures. The occurrence of this injury provides a good example of difficulties that may be encountered when introduced trees are not completely adapted to the environment.