Keep living Christmas trees in the house only seven to 10 days. Otherwise, the buds will break dormancy, start to develop and lose their ability to withstand cold. When a tree that’s no longer dormant is placed outside in the cold, it rarely survives. However, it’s possible to reactivate dormancy by gradually exposing the tree to colder temperatures over a period of weeks. This requires moving the tree out during the day when temperatures are above freezing and back in at night if temperatures are at or below freezing. Progressively expose the tree to colder and, eventually, freezing temperatures. At that point it can safely be planted outside.
The alternative to moving the tree in and out every day, is to baby it indoors until temperatures stay above freezing in the spring. Keep it in a bright cool location where the temperature stays above freezing. The soil should stay moist, but not soggy, whether you’re keeping it inside until spring or encouraging it to go dormant again.
Leaving a tree in its container outdoors over winter is problematic. Containerized plants freeze, thaw and reheat more easily than plants in the ground. This stresses the tree, damages roots and compromises the plant’s ability to absorb water. If you must leave a tree in its container outside, try packing snow or soil over and around the pot for the winter. Another option is to build a wire cage around the pot and fill it with mulch, soil, leaves or straw to insulate the roots. Keep the tree in a shady location out of drying winds, if possible, and maintain soil moisture without letting the tree stand in water.
While the tree is indoors for your celebration, place it in a cool bright location away from any heat source or direct sun to avoid drying out its needles. Check soil moisture daily and water when the top two inches of soil feels dry. Remember to put a plastic saucer underneath first. Set the container up on rocks or another upside-down saucer within the drain pan to prevent the plant standing in water.
If the tree is still dormant after the holiday, plant it immediately. Prepare the hole before the ground freezes. If you don’t dig the hole in advance, a couple of warm days or a few buckets of hot water poured on the ground should let you dig a planting hole after Christmas.
A little care will allow you to enjoy your tree for years to come.
JoAnne Skelly is associate professor and Extension educator, Emerita at University of Nevada Cooperative Extension. She can be reached at email@example.com.