Even though it’s late in the season, your shrubs will be happier in the ground than in pots. Ideally, trees and shrubs need about a month to establish roots before a heavy freeze, but it’s actually ok to plant them anytime the ground is workable.
Here are a few tips for seeing your late-season plantings through the winter:
Avoid stimulating growth: Don’t fertilize or overly amend the soil. You can add a little compost and bone meal (to stimulate root growth), but hold off on fertilizer until spring.
Don’t disturb the plant: Avoid pruning, and be very gentle with the roots while planting. The shrub won’t have time to recover from damage, and it’s going to be stressed enough as it is.
Keep plants watered: The worst part of cold damage is caused by desiccation, or drying out. Keep new shrubs watered every week or two until the ground freezes, and especially right before a heavy freeze.
Watch out for frost heaving.
Apply Mulch: Add mulch to keep newly planted shrubs insulated. If you’re planting cold-sensitive trees or shrubs, you can add extra protection by wrapping or banking the plants with burlap or leaves on cold nights. Be sure to uncover in the morning.
If the ground is frozen solid and unworkable, you can store unplanted shrubs in a sheltered spot with a southern exposure until able to plant. Bank with leaves or mulch to keep them insulated and make sure to water. Once growth starts in early spring, prune away any damaged branches, shape up your plants, feed with a balanced fertilizer, and they should recover nicely.
The only trees you should totally avoid planting in winter are evergreens. Unlike deciduous trees and shrubs, evergreens hold on to their foliage in wintertime, and it’d be really hard for them to establish their roots and preserve their needles’ moisture levels with a limited water supply in winter.
