Installation
Planting a new tree too deep is one of the leading causes of new tree mortality. Typically the top of the root ball should be installed level to the ground surface of the yard. In New Hope where heavy clay soils can present issues to new tree growth, the root ball many be raised so that up to 1/3 of the ball is above ground level. This promotes the spread of lateral roots.
Watering
Newly planted trees require routine water. Typically a tree requires 5 to 7 gallons of water applied directly to the root ball per week. The best way to water a new tree is to leave a garden hose trickling at the root ball for a few hours. This promotes deep growth of roots. In contrast, watering large amount at a time to the root ball directly promotes the growth of shallow roots. Watering in the fall needs to be closely monitored to ensure the tree can go dormant at the correct times.
Mulching
Keeping up to a 5" layer of mulch around new tree bases is a very important part of new tree care. Mulching allows for the better infiltration of water, the retention of soil moisture, limiting weed and grass growth, and discourages damage from lawn mowers or weed whips. Keep the mulch material away from the trunk. A porous landscape fabric that allows for water and gas exchange can help prevent weed growth, but a plastic landscape material can cause roots to suffocate and is not recommended.
Fertilization
Fertilization of newly planted trees may be done every 2 to 3 years. Fertilizer can be applied either in the fall after leaves have fallen or in early spring before growth begins. Fertilizers can be applied to the ground surface surrounding the tree or by placing it in holes around the tree. Keep in mind that fertilizers applied to turf grass surrounding the tree may burn out and kill the turf, and surface applications typically must be watered in. Do not apply nitrogen fertilizers in the late summer as they can promote new growth that will not harden for winter properly. Phosphorous and potassium fertilizers can be applied into the fall as they typically enhance winter acclimation of the tree.
Staking
Contrary to popular belief most new trees will do much better without staking. Young trees allowed to stand alone tend to develop stronger, more resilient trunks and root systems than trees that are staked. If a tree is unable to stand along then staking can be a solution but it must be done carefully. A very common problem with staked trees is that where the tree is wrapped the bark will die and cause irreparable damage to the tree. Soft nylon webbing or carpet strips attached to grommets can reduce the damage to tree trunks. If staking is necessary, remove the stakes and ties once the tree is established.
Winter Care
Proper winter care begins in the summer! Watering should be decreased in the early fall to prevent new growth, and should be increased in late fall to provided the necessary water to the tree to withstand the upcoming winter. Do not encourage late growth by heavy watering and use of nitrogen fertilizers in the early fall. In the late fall plants should be thoroughly watered up until the first soil freeze.
On new trees or trees with bark damage the trunk from the base to the first branch should be wrapped with a commercial tree wrap. This helps avoid Sunscald, the sunken dried out and cracked bark that can be caused by the sun heating the tree's bark during a cold winter.
Animal damage can also be severe during Minnesota winters. New trees should be protected from rabbits and mice by installing an animal barrier. Either a cylinder of 1/4 nich mesh hardware cloth or a plastic drain tile pipe can provide an adequate barrier. Whatever material is installed it should be black and should extend 2' higher than the expected snow level. Chemical application can also be applied directly to the trunk.
Pruning
After planting a new tree only prune critical branches and no others. Prune only branches that are broken or dead, or if there are competing leaders. Minimize all pruning at the time of planting, as trees need as many leaves as possible to recover from transplant shock.