How do you prepare potted perennial herbs for winter outside?
Question:
I have several perennial herbs in five separate gallon containers that I can’t bring into my house for the winter. What is the best way to prepare these plants to winter over outside? I do have a baker roof attached to my garage that I could store them under. Should I cut them back? This is my first year growing herbs and they did well. I would like them to come back in the spring.
Answer:
Winter hardy perennial herbs can indeed be overwintered outdoors, but you are correct that they need a bit of preparation–especially potted ones, as the unprotected soil will freeze faster than root balls planted in the ground. The good news is that your attached shed can be an ideal space for the project. The main goals are to insulate the root ball and protect the plants from wind. Cut the herbs back after the first frost (pruning them too early can induce an unwanted flush of new growth right at the end of the season, and you want the plants’ resources concentrated in the roots and crown) to decrease the amount of plant tissue that will release water through evaporative transpiration. A nice, 2-3″ thick layer of mulch in the pot will help protect the root ball, and bales of straw, stacks of bound newspaper, rolls of landscape fabric, etc. piled up and around the pots will keep dehydrating winds from getting in. If you have access to floating row cover, a blanket on top of the area can help insulate the herbs, as well.
I will caution that there is never a guarantee with overwintering herbs outdoors in pots, but the tips above will give your plants the best chance of weathering the cold and being ready for spring growth.