That's a page that every gardener should have bookmarked. I'm not with Dr. Linda absolutely all the time, but there is a huge wealth of practical knowledge and good advice here.
I totally agree with this. Ron has generously given the link before and I think it's a great resource. She has the ability to explain things in easy to understand common language which does not leave the average reader feeling beneath her or still left in the dark and yet enough educated and intellectual words/terms to make it interesting for any researcher to enjoy and appreciate. The other page she contributes on along with other associates is also beneficial to follow. She does a number of Podcasts as well off this page with links. You may also comment and ask questions. WSU Extension: The Garden Professors ==========
This generic statement is generally wrong and not supported by research. It depends on which climate zone the tree is growing. The latest article I've read on the subject is: 'Low temperature limits of root growth in deciduous and evergreen temperate tree species', by P.Alvarez-Uria and C. Korner, University of Basel, Functional Ecology 2007. They studied 6 species: Alnus viridis, Alnus glutinosa, Picea abies, Pinus sylvestris, Betula pendula and Pinus cembra. Thir main conclusions are: 1. Five of the six species produced hardly any (<3%) new roots at soil temperatures below 6°C, while Betula pendula produced a few roots. 2. Across all species, 85% of all new roots in the cold profile were confined to the rooting zone above 9°C 3. Low and high elevation taxa did not differ in any of the traits or responses tested. Thus, for those species tested, and tentatively extrapolating to other deciduous and evergreen temperate tree species, the critical soil temperature for significant root growth is 6°C; some growth occurs between 6°C and 9°C and strong growth occurs when root-zone temperature reaches 9°C. Gomero
Interesting, I was always wondering if trees are still producing root growth in the winter. Here in mild Vancouver, our winter's have an average high of 7°C and low of 1°C. Since the soil temperature would be warmer, could I expect some growth occuring?
Squeezied, as the quoted article states, if the root-zone temperature is >6°C, then there is root growth. In my climate I have estimated that, in a typical winter, roughly 50% of the time the root-zone temperature is at 9°C and above. I have indeed seen significant root growth in some maples placed in the ground in late fall and transplanted in early spring. Gomero
