How to overwinter a container-grown tree

container-grown tree
I chose to store my American sycamore tree in an unheated garage for the winter because the ground was already frozen when I received it. Sara Welch photo.

I recently had a birthday and one of my favorite gifts was an American sycamore tree. Their distinct bark makes them one of the easiest trees to identify in the winter. Its smooth and nearly white towards the top of the trunk and on the branches with blotches of grey and sometimes rust colored bark speckling it further down the trunk. Its unique appearance makes sycamores one of my favorite trees.

The only problem with a birthday in the middle of December is that the weather doesn’t always make it an ideal time for planting trees. I got snow for my birthday and the ground froze, making it impossible to even consider planting my tree outdoors.

Fortunately, when trees can’t be planted outdoors before winter, there are steps you can take to ensure it survives in its container.

Maintaining the right temperature

Container-grown trees shouldn’t be left outdoors, above ground during the winter because the temperature of the potting mix may drop into single digits and damage their delicate root systems.

Container-grown trees also shouldn’t be kept in a heated space indoors because the tree should remain dormant throughout the winter until spring. 

There are a couple overwintering options to protect the root system of your tree without bringing it out of a dormant state.

Bury the container

One way to overwinter container-grown trees is by burying the container in your garden outdoors. Dig a hole, set the pot in the hole and cover it with soil all the way around to keep the roots insulated throughout winter. Trees should be dormant before containers are set into the ground, however, the entire process should be completed before the soil freezes — no later then a few weeks after the first frost in the fall.

Containers can be removed from the soil in the spring when extreme winter temperatures have passed and the soil thaws — several weeks before the last frost date in the spring.

Buried container-grown trees will only need watered in the fall before the soil freezes and after it thaws in the spring. Supplemental watering isn’t necessary when the soil is frozen. Keep in mind that buried containers will require less watering than if they were above ground and overwatering can cause diseases.

Trees that are overwintered outdoors will need to be protected from hungry deer, rabbits and other animals throughout the winter. Chicken wire fencing can be used to create a barrier and protect your tree, but it needs to be tall enough to prevent access after a heavy snow. Tree wrap or plastic tree tubes can be used to prevent animals from stripping your tree’s bark.

Overwinter in an unheated garage

I couldn’t overwinter my tree using the first method because the ground was already frozen when I received it. Instead, I prepared it to be overwintered in an unheated garage.

Container-grown trees can be overwintered in a moderately-cold location where the temperature ranges from 20-45 F during the winter. These temperatures will keep the tree dormant until spring without damaging its root system.

An unattached, unheated garage is often an ideal location for maintaining the correct temperature range to overwinter a tree. If you’re concerned the temperature is varying more widely, monitor and adjust the temperature inside the structure as needed.

The tricky part about overwintering trees in this situation is monitoring and maintaining the moisture levels of the soil. Moisture levels should be checked often and the tree should be watered whenever necessary. In an unheated garage, your tree may need watered as frequently as once every two weeks when temperatures are above freezing. Again, it’s also important to avoid overwatering your tree. The soil should be kept moist, but not soggy.



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Sara is Farm and Dairy’s managing editor. Raised in Portage County, Ohio, she earned a magazine journalism degree from Kent State University. She enjoys spending time with her daughter, traveling, writing, reading and being outdoors.



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