How cold is too cold for trees?   shamr-@aol.com   Jan 17, 2007 13:56 PST  ENTS, Last night it got down to -21f, cold enough to freeze the cold water line in my kitchen despite the nearby woodstove. Today the temp. climbed all the way up to -5. All this cold has me wondering about the effects of cold on different tree species. I know the trees outside my window (mostly fir, spruce, and birch along with a fair number of maples, pines, cedar, aspen and cherries) are all pretty well adapted to the current temperatures, but are there certain species that will die simply from a long enough exposure to a cold enough temperature? Tim RE: How cold is too cold for trees?   Steve Galehouse   Jan 17, 2007 15:26 PST  Tim, ENTS- From a nurseryman's perspective, I feel that root hardiness is often the limiting factor for woody plants-certainly Thuja occidentalis and Picea glauca are more root hardy than Chameaecyparis or most Pinus species, from experience gleaned from over-wintering plant material. Top hardiness seems to always be greater than root hardiness temperate species, at least, and snow cover is beneficial for moderating root zone temps. I've yet to see truly native trees in my area that have been injured by winter temps, although late spring frosts can wreak havoc on tulip-trees especially. Tree species which are native, but planted and used as ornamentals, often show winter damage, but this is a function of provenance-redbuds and dogwoods in the nursery trade generally are derived from mid-South genetic material, and are often damaged, while the naturally occurring trees of the same species are not damaged. Steve Galehouse Re: How cold is too cold for trees?   Lee Frelich   Jan 17, 2007 15:34 PST  Tim: -21 f is not very cold--you don't have to worry about your trees dying from those relatively warm low temperatures. If you had sweet gum or live oak, temps in the -20 range would be a problem. Northern hardwoods from northern states can go as low as -47 before the cambium will be killed. There is a lot of variability in minimum temperatures tolerated by trees from different parts of the range within one species. Red maple, for example. One study showed that red maple from the southern states had cold damage at -20, but for red maple from northern states, -45 was necessary to cause damage. White spruce also had a lot of variability. Those trees from WI could only withstand minimum temps of -55, but trees from Alaska could take -70. Some species can withstand amazing temperatures, for example a bald cypress planted in Grand Rapids, MN. Minimums of -40 to -50 have occurred and the tree has not had any damage. Ditto for some cypress and cucumber magnolia in Minneapolis that have withstood -30 to -35 without damage. Don't forget how much the climate has warmed in the last 300 years. In the late 1700s people could walk from Manhattan to Staten Island on the ice, and in London vendors had a market set up on the Thames River for a few months each winter. Most of our forest trees still have the adaptations to that climate. Lee Re: How cold is too cold for trees?   Neil Pederson   Jan 17, 2007 16:31 PST  Tim, ENTS, Snow cover is an important factor. Research conducted in the White Mtns of New Hampshire showed a 50% increase in fine root mortality in plots that had the snow cover removed. This was during the two relatively mild winters of '97-'98 and '98-'99, I believe. Terrible work for the techs on that project [shoveling a forest]. Great results, though. Neil   Home