We have two boxwoods in plastic pots on our covered porch. The temperatures are dropping in the teens: what should we do to protect them?
The Gardener’s Answer
Planting evergreens in containers is a great way to add winter interest to any space. There is always a risk when doing this, especially if you live where winter temperatures dip below freezing for any extended amount of time. Different species of boxwoods vary in terms of hardiness, but most are considered hardy to zone 6 and will survive temperatures as low as -10 degrees F.
The main concern with evergreens in containers is that they dry out faster and do not have the warmth of the surrounding soil like those planted in the ground. The goal is for them not to go into dormancy without sufficient moisture, as this makes them more susceptible to winter burn. As the soil thaws, make sure to hand water if they are not in a position to receive rain or snow and check that the containers have drainage holes.
Add a few inches of mulch to the top of the soil for insulation. While it may not look very nice, surrounding the containers with straw bales or wrapping with blankets will also help insulate them. This helps to prevent excessive freezing and thawing cycles, which can damage roots and potentially kill the plants. The good news is that plants do not feel wind chill so temperatures in the teens should not damage your boxwoods.