Cold Sensitivity of Field-Grown Allocasuarina and Casuarina Tree Species

Abstract

The sheoak genera, Allocasuarina and Casuarina, contain a diverse range of Australian trees and shrubs of both ecological and economic importance. Although they are well known for tolerance to stressors such as drought, salinity and high temperatures, their tolerance to freezing has not been adequately examined. Some data has been published on the cold sensitivity of Casuarina cunninghamiana but other Casuarina spp. and no Allocasuarina sp. have been assessed. This study examined growth and survival of field-established Allocasuarina (2 species) and Casuarina (4 species) in Central Anatolia, Turkey with winter temperatures dropping to −15°C. Following establishment in May 2020, the accessions tested (100 plants in total) mostly grew well during summer and autumn in this semi-arid climate with mildly alkaline soil, but the shoots of all plants were killed by the extreme cold of winter, with only seven plants producing weak root sucking in the summer of 2021, which all subsequently died. Although both genera appear to be cold sensitive, the results indicate the merit for wider evaluation of sheoaks in other contexts with harsh environments but not in regions exposed to periods (even if relatively short) of subzero temperatures.