I don't get it. Is it rocket science??
Rocket Science? Absolutely Not!
However...........there are a number of issues.
Here's one overview that covers some....its more aimed at homeowners, but the gist applies to all transplanted trees.
http://www.isaontario.com/content/tree-planting-tips-myths
My take:
First, you have to correctly understand the conditions into which you need to plant your tree; and pick the species accordingly.
Its not merely sun/shade/or mixed; its dry/moist/wet/, its windy, its poorly drained vs well drained; its high-nutrient vs low; its how much pollution and/or salt and/or dog urine a tree may be subject to. Ever seen new Cedar trees turn black? (dog urine) kills them.
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So now you've got your conditions down; you have to pick a tree that fits the conditions and/or amend the conditions, where possible. (unlikely you can change the climate or sun levels, but you can 'amend' soil to sustain different vegetation..........however, you may need to 'sustain' the amendment, depending on the conditions'
No amount of care will make a tree that doesn't belong in 'climate x' thrive.........it may sustain it for a time..........but you won't win a war w/nature on the tree's behalf.
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Now you need to know that trees are best planted when dormant....that means no leaves or growth occurring; its a lower-stress time for planting. Its not impossible to plant mid-summer; however, it is harder on the tree, and your survival rate will decline; and your work-effort to sustain it will be higher.
Dormancy is essentially when most of the leaves have fallen off..........until prior to leafing-out in mid-spring. So, in Ontario, mid-October to early May. The shoulders of that aren't too bad either (the balance of May, and October).....much more into summer and challenges arise.
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From there you need to know most transplanted trees when young are aimed to have a 70% survival rate; if properly planted, in the right season, its closer to 80% (as measure over 3 years from the date of planting)
However, the larger the tree, the lower the survival rate..........you have to realize that a big tree, needs big roots.....typically as wide below ground as the widest branches.
But that makes it materially more difficult to fit into planters/pits or all but the largest of holes, so the roots tend to be substantially trimmed before transplant. This cuts your survival rate to under 60%
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Finally, you need to plan your planting (when done on a large scale), to account for genetic diversity. This is not merely an academic exercise. If all trees chosen are in the same genus/family they are likely vulnerable to the same diseases and pests. Hence the city is losing over 90% of its Ash trees due to Emerald Ash Borer. Choosing all one species means that if a disease or pest arrives, you could lose 100% of your trees! Its just no way to plan a planting.
Soooo, not rocket science............but a few things to consider to get it right.
What Yorkville did wrong..............poor species choice; only one species chosen; previous plantings (not the last round) occurred in fall, before dormancy; a less than optimal
choice.
Its my understanding that AA chose the tree species............they should bow their heads in shame.