It’s a good time of year to see tree health because the trees which are struggling will already have started to change colour and subsequently drop their leaves, before other trees of the same species around them.
On our recent Tree Walk which started at Guelph City Hall, the Kentucky Coffee trees planted in pits under the pavement clearly show this as compared to those planted in the raised beds. As we walked along Waterloo St. to Edinburgh Rd. we focused on the trees planted 20 to 40 years ago, and of the 80 we saw along these 4 blocks, only a quarter showed good health. But the boulevards and the available soil mass for the trees is very large, so why have their lives been so shortened? Salt is not the issue here – the soil mass is too great. These trees have reached the end of their lives because their root systems never developed! Why?
Here is a list of reasons – nursery techniques of cutting roots, and root circling as a result; not planting trees when young and vigorous; planting trees in isolation so the roots bake/freeze; such short growing periods; compacted sub-grades resulting in difficult or impossible deep root access for water uptake in summer; challenge in winning the competition with grass for available water; trees planted too far apart for aesthetic reasons – in Nature trees live near each other; use of non-native species (this is changing under the new planting policy).
The important thing to note here is that there was lots of room and soil mass for these trees to prosper and meet the intent of creating a lovely wide street with a towering canopy (there are some very large old Maples as examples planted 150 years ago, so it is possible). These trees’ deaths now show how our planting policies not only cause frustration from losing young trees and not having a beautiful avenue, but also bring the expense of replanting.
So our focus must be ‘what do the roots of the replacement trees need this time to succeed?’ Look at each of the reasons they failed outlined above and then use alternatives – younger plants planted with shrubs on raised soil areas as seeing in front of City Hall; succession planning with fast and slow growing trees planted near each other and many more techniques focusing on roots and soils. If we prioritize the root health when we plant trees, with the desire and intent that they live the hundreds of years we want them to (as nature does) then the trees will adapt to being transplanted, much the same as we do as we move around our cities and homes.