One of the most frequent questions I’m asked is: “When is the best time to plant a tree?” To their surprise, I respond unequivocally that winter is the best time to plant a tree.
This is for various reasons; first and foremost, all plants are in a state of “hibernation” if you will, and as a result, the inevitable shock of transplant is reduced significantly.
Cooler temperatures, combined with the fact that deciduous trees are leafless and evergreens have a much reduced photosynthetic rate during this season, means less water loss during transportation of the tree from the nursery to the planting site. When a tree is planted, it is a good idea to prune some of the roots in order to stimulate new root growth into the new soil and undo some of the bad root growth practices of girdling roots that occurs in container-grown plants. What little growth that occurs in plants during the winter is underground, at the root system level. Winter planting gives a tree a head start for quicker establishment in the critical first year. Ironically, the spring and summer are the busiest planting times for those in the green industry, so winter planting is typically faster and can possibly result in reduced costs for new tree planting. Finally, water frequency is significantly diminished for the tree, making it a little easier on the caretaker who can appreciate easing into a new routine of care and monitoring for the new tree(s).
When purchasing a tree, look for ones that are grown in wooden boxes.
A wooden box construction means a heavy root ball—the most important part of the tree. Also ask if the tree will need to be staked and guyed after planting. If so, that means they are selling you a tree with a poor root ball. The new tree’s root ball should be at the same grade as the original soil grade. The hole should be approximately 20–30% wider than the actual root ball. Care should be taken to avoid any fracturing of the root ball as it leaves the container to its place in the hole. The first 6–8" of trunk should be straight; if the canopy is not straight then prune and/or guy the tree as opposed to putting the trunk in leaning. Stick a hose next to the bottom of the root ball prior to backfilling and water at a moderate to slow rate of flow after the backfilling is mostly completed. Backfill should be all native soil and some organic amendments between 15–35%. Put extra soil in a big mound over backfill and in a ring around it, as soil will settle and watering can be funneled directly into the root ball. Slow-release tree bags are a great choice for watering. Many will prefer a tree bubbler for automated watering: just make sure you have a water-wise system with rain sensors installed, and remember that drought water restrictions (whether they are in force or off) of watering only once a week are more than adequate for even newly planted trees during the entirety of winter. Finally, deer and porcupines will utterly destroy your tree! Do not plant trees without fence protection.