Not everything we do for trees is good for them. Here are the top planting practices that harm trees and shrubs.
Amending the soil when planting a tree is harmful.
We’ve been told that amending soil when planting a tree gives it a good start, but many studies prove that this could actually harm your tree. In the short term, amendments give your tree a boost. What plant doesn’t like organic amendments? But once the roots grow to the boundary of the amended planting hole, they tend to circle or girdle, especially if you have clay soil. As well, the differences in soil textures impedes the movement of water and restricts root establishment. Over time, a constricted root mass stresses the plant, leading to restricted growth and other problems.
Planting too deep is harmful.
It can be hard to know how deep to set your tree into the planting hole. It is essential that the trunk flare is visible – either level with or just above the natural grade of the soil. The trunk flare is the widest part of the base of the trunk, just above the main roots. The trunk flare is covered in bark; roots are not. Burying the trunk flare causes the bark to rot and this interferes with the uptake of water and nutrients. Other symptoms include: slow growth rate, thick canopy and early dieback.
Not correcting circling or girdling roots is harmful.
Trees grown in containers may have roots that are circling, girdled or densely growing in the container. Left as they are, the roots tend to remain in a tight ball – they need to grow outward for proper growth and development. This can result in branch dieback, progressively thinning canopy and early tree death. It’s important to prune or tease out circling roots so that they grow outwards, like spokes on a wheel.
Leaving packaging materials on the roots is harmful.
If you have a balled and burlapped tree, there may be burlap or a wire basket around the root ball. This helps to keep the root ball intact until it is ready for planting, but interferes with root growth if left on after planting. This may result in a slow growth rate, gradual decline in tree health and ultimately the death of the tree. Remove all packaging materials for a healthier tree.
Using stakes and ties and leaving plant tags on is harmful.
Staking trees is seldom necessary. Research has shown that un-staked newly planted trees establish faster and produce stronger roots compared to staked trees. Most trees do not need to be staked. The exception is if the tree is consistently exposed to strong winds. Staking is used to anchor the root ball but must not prevent some movement of the trunk. Constriction or rubbing of the bark from ties and plant tags cause further problems like branch dieback and early death of the tree.
Not watering enough for several years after planting.
The rule with planting perennials is "water little once established" but how long does it take for a tree to establish? Most of us are great at watering our new plants for the first few weeks but it can take several years for a tree to grow sufficient roots to get established. It's critical to mulch the planting hole (though no mulch against the tree itself) and water deeply and frequently throughout the first year, especially if you needed to root-prune when planting. Water deeply again in late fall to protect the tree throughout winter. You still need to provide supplemental water the second year too, albeit not as frequently. By the third year, you can either eliminate or begin to reduce your watering of the tree - use your best judgement here taking the weather and the amount of root pruning you did during planting into consideration. Do not continue watering a tree after the third year unless there is significant unusual drought as trees will grow in response to whatever water and nutrients are available to them, and then die back when these are no longer available. You'll be doing more harm than good if you continue looking after it too carefully once it establishes itself in your native soil.
Sources
https://s3.wp.wsu.edu/uploads/sites/403/2015/03/soil-amendments.pdf
https://s3.wp.wsu.edu/uploads/sites/403/2015/03/fragile-roots.pdf
https://s3.wp.wsu.edu/uploads/sites/403/2015/03/wire-baskets.pdf