During a warm-spell in early winter, can dormant hardwoods survive planting? Even if frozen temps are a day away?

Question

Zone 5 northeast USA has had an early winter in some places, getting slammed with many evenings in the 20s and a few even lower. Some snow but it's come and gone, eventually melting after a couple weeks. A warm spell has melted most snow recently and the ground is still soft, it didn't freeze deep yet.

Can a dormant hardwood tree be planted in the soil if it's not frozen? What if temperatures will drop below freezing the night or coming days after planting? I have some potted trees and spots ready to dig for them! Winter weather came early so I didn't plant them earlier in the fall.

My understanding is yes as long as the trees are totally dormant before transplanting. In terms of planting I've heard to pack the soil a little compressed and add lots of mulch on top to help prevent frost heave from throwing the tree back out from the ground!

Answer 1

My own experience is that planting the hardwoods now will work, even if the soil freezes soon afterwords. This is one time when planting a potted plant, though, that I would NOT try to break the root ball a bit to encourage rooting into the soil.

You have three major concerns, though:

1. Current location - Where are the potted trees stored right now? A semi-heated basement? Outside shed? Attached garage? If your pots are in a heated area, I do not think I would attempt the transplant because they aren't acclimated to the cold. I think (and I don't have scientific proof on this) that you risk killing the small trunk and stems by moving them from 60-70 degrees F to near-freezing or lower temps. This may be too much caution on my part, however.

2. Frost heave - As you noted, it's important that you compress the soil a bit to ensure few/no air voids around the roots but you don't mulch until the ground freezes thoroughly. The mulch isn't there to protect the roots from getting too cold, it's there to prevent the frozen ground from thawing during warm spells in the winter. You can mulch it fairly deeply (I'd still try to keep it from around the trunk as much as possible) and remove excess mulch when spring arrives.

3. Critters - Voles love woody plants, and your freshly planted trees could be stripped of bark in an hour. I've also had Rabbit damage on smaller woodies, where the rabbits snip the stems off not to eat but for their teeth, I think. If the pots are 2-gallon or large, here's a suggestion: protect each tree with a sleeve made from quarter-inch mesh (sometimes called hardware cloth), set it below ground level as you backfill the tree, then staple it to the ground. When the ground freezes, put a lot of mulch on the outside of the sleeve. This means that you would have to mulch a bit inside the sleeve before the ground froze. You could still try this with smaller pots and trees, but you would certainly have to stake the sleeves.