The city of Toronto planted a bare root Red Maple tree on the boulevard in response to my request for a tree that turns brilliant vibrant red colour in fall. The tree was planted May 13, 2015. The tree has yet to display any red colour and turned pale yellow and brown.
My questions are as follows: Is my tree a Red Maple? Will the fall colours displayed last year and this year be the colours I should expect in the future?
What Red Maple cultivar does the city plant?
The City of Toronto’s brochure “Help keep our urban forest growing – Let us plant a tree” sets out 4 maples that residents may select for planting by the City: Black maple (Acer nigrum), Red maple (Acer rubrum), Sugar maple (Acer saccharum) and Silver maple (Acer saccharinum). It is not possible from your photo to identify the tree, but it could be a red maple.
Leaves of the red maple tree usually turn red in the fall, but may be orange or yellow in colour. There may be quite a bit of variation in leaf colour from year to year, as growing conditions and weather play a huge role. For example, a dry summer and bright, cool, sunny autumn will bring the most vibrant colours. As we head into winter, the shorter days trigger the tree to get ready to hibernate – this includes reducing concentrations of the green pigment, chlorophyll. As this happens, other pigments become more apparent – for example, carotenoids, which are responsible for the yellow colour. Anthocyanins, which produce bright red colours, are produced by sugars present in the leaves. Sugars are formed best when the fall days are sunny, while cool evenings will keep these pigments in the leaves. And some maple species have a genetic makeup that causes them to transfer sugars more slowly than other species – these would be likely to have the showy red colours in autumn. See the University of Tennessee’s Changing colours of leaves. It is not clear whether your tree’s leaves will be similar year after year – take a look at your neighbours’ maple trees – if planted by the City, they will likely show a similar colour palette, although different cultivars will show variation in leaf colour.
As for cultivar the City planted in your yard, it’s hard to say what it was – unfortunately, the City does not provide detailed information on their website. Why not call the City — just dial 311– and ask them directly? Make sure you provide them with your address as well as the date of planting, as they may use different cultivars at different times.