A typical fall question that many homeowners ask us is, “When is it too late to plant a tree?” The average rule of thumb is that fall plantings do best when they're in the ground and starting to root no later than 6 weeks before the ground freezes. Though that can vary from year to year, on average, that timing works out to around the end of November in Minnesota.
That doesn't mean trees and shrubs are doomed if you can't plant them by the end of November. It simply means that the later you go; the odds of successful tree growth begin to drop.
Here are a few tips for seeing your late-season plantings through the winter:
o Avoid stimulating growth: Never fertilize or overly amend the soil. At the very minimum, add a little compost or even bone meal to help stimulate growth. However, avoid fertilizing until at least early spring.
o Be careful with the plant: Avoid pruning, and be very gentle with the roots while planting. With the winter months coming, the plant will be stressed enough as it is, so avoid any disturbance if possible.
o Keep the tree watered: The cold weather can cause a plant to lose moisture and dry out. Keep any new tree or shrub watered every week until the ground freezes, especially right before a heavy freeze.
o Watch out for frost heaving: Make sure the plants stay firmly planted when the ground freezes. Any tilt or uprooted lean can cause extreme stress to a newly planted tree.
o Apply mulch: Mulch will help keep the tree insulated from the harsh weather. It will also help the newly planted tree retain water.
Pro tip: If the ground is already frozen and impossible to work with, you can still store the unplanted tree or shrub in a sheltered spot with sun exposure. Pack with leaves and mulch to keep the tree insulated and water every couple of days. When the tree begins to grow, prune away any damaged branches, fertilize and the tree can be planted come spring.