It seems that about 90% of all the leaves on the trees in my neighbourhood in Toronto have fallen in the last day or two. Due to unseasonably warm fall weather and a very dry summer, the leaves have been very late turning.
Toronto arborist Todd Irvine has posted about the situation on the Spacing Toronto blog. The other day he gave an interview for Global Television from a helicopter and he describes what he saw that day. As well, he posts a bunch of fascinating photos showing the truly marvelous tree cover in Toronto neighbourhoods. A great post about the interface between the natural world and our built up spaces, not just vitally interesting to self-absorbed Torontonians but to everyone interested in the past, present and future of our cities.
The vibrancy of the colours and the time the leaves drop is dictated by temperature, available moisture, and most importantly, shorter days. This year, as a result of the long summer drought, followed by a mild fall with no frost and cool rains, trees are holding their leaves longer. They are doing so partially to take advantage of the unseasonably good growing conditions by storing extra sugars they were unable to during the summer, because of the crippling drought.
One fear is that we will now have a heavy snowfall or ice storm, which is more than likely considering it is mid-November. If leaves are still on the trees and the conditions are just right, snow and ice will stick to them, greatly increasing the weight of each limb, causing some limbs to break. The impact on the urban forest, not to mention the people and property below could be significant —all the more reason to have an ISA certified arborist routinely check the condition of trees on your property and conduct preventive maintenance if required, so they will be much less likely to suffer damage.