FROST RING FORMATION IN SOME WINTER–INJURED DECIDUOUS TREES AND SHRUBS

Abstract

Winter injury, occurring either in late fall or early spring, has ever been a serious menace to vegetation, and the injurious effects frequently incurred by freezing are well knownl. The latter part of February, 1932, was characterized throughout Illinois by the prevalence of temperature conditionls so exceptionally mild that growth activities were initiated in a number of kinds of woody perennlials which would have maintained, otherwise, a more prolonged period of dormancy. The occurrence of a sudden freeze in early March, however, abruptly checked and injured this premature vegetative growth; and continuation of low temperatures into late March caused vegetative activity to remain in a state of dormancy for almost a month. In the vicinity of Champaign and Urbana, winter injury was manifested in various trees and shrubs in that their subsequent growth was conspicuously altered upon the recurrence of temperatures favorable to growth. This injury ranged in extent from only slight to very severe and was exhibited particularly by elm, pussy willow, poplar, and privet, and to a lesser extent by maple and other plants. In view of the general prevalence of winter injury the past spring, its occurrence in past years, and the probability of its recurrence in the future, it seems advisable to present herewith some studies and observations made in relation to winter injury in the Champaign and tTrbalna vicinity as an aid toward a fuller knowled;e of its character. Accordingly, the general symptoms of winter injury are described, as well as some of the special symptoms exhibited by a few of the more severely and commonly injured trees and shrubs. Histological studies of frost ring formation in Ligustrwui have been made, with a comparative histological treatment of Ulmtus, Popults, and Salix.