Trees as long-range weather forecasters?

At this time of year we are busy lifting trees and despatching them to their purchasers, and so we regularly inspect the roots of hundreds of two to three-year old trees. From the appearance of the roots, we can judge the period of dormancy of the trees, and so, on the website, this season we recommend planting from December to April.

This is later than normal. In fact, the usual dormancy period is from November to March. But the winter of 2013-2014 wasn’t particularly cold, neither were spring and summer 2014. So why is the dormancy period later this year, and how can we tell?

I should start with a bit of background information on how the roots work. The feeding roots – tiny and delicate capillary roots invisible to the naked eye – operate from April to September. Then they begin to shut down, and the tree stores resources in the trunk and main root stems. At a certain stage, usually in mid January, white roots begin to emerge from the main root stems. These are not functional as roots, but just serve to establish the initial structure from which the feeding roots will develop. This year, today, 2 February 2015, not one of the trees has begun to develop these white roots. What is the reason for this?

It’s as if the trees know that there is no point in developing their root system yet, because the weather is going to be colder than usual over the next couple of months. How do the trees know this? Perhaps they have a sensitivity to certain meteorological parameters that enable them to time the moment at they begin preparing for the end of dormancy.

And so, on the basis of my observations, I would venture to say that it will be a long, cold winter, or at least longer and colder than usual. And whatever happens, whether right or wrong, I am convinced that the world of plants still holds a lot of mysteries that still awaits scientific explanation.

(In the photo below, we partially lifted a young tree to show the brown roots. We couldn’t find any white roots at all!)