NaCl and twig dieback along highways and cold hardiness of highway versus garden twigs

Abstract

The timing and amount of stem damage and bud kill, along with the Cl content of twigs, were observed over one or two winters in Fraxinus pennsylvanica Marsh, Cornus stolonifera Michx, Malus sp. cv. Hopa, Salix pentandra L., and Syringa vulgaris L. growing along Minnesota highways. Depending on species and the year, damage occurred between January and May.Cold hardiness was compared for highway- and garden-grown Syringa vulgaris L. and Fraxinus pennsylvanica Marsh. Hardiness was assessed as percentage of xylem and cambial browning and percentage of bud kill after exposure to test temperatures between −45 and +4 °C. In November, hardiness was the same, but from mid-December into March, highway twigs showed more damage than garden twigs at the same test temperatures. The differences between highway and garden twigs coincided in time with differences in twig Cl.