How should I take care of my potted blueberry and raspberry plants during the winter? Do they require straw or coverings, and if so, what types work best?
The Gardener’s Answer
Hello, Katherine: Growing blueberries in containers has its benefits in terms of space and adjusting the soil pH, but we do need to take extra precautions to help protect them over the winter months. Depending on variety, most blueberries are very cold hardy; some can take temperatures well below zero. As a general rule, blueberries are very shallow rooted, which makes them easier to grow in containers but the roots will need protection from the cold weather. Adding a layer of mulch, a couple inches thick, on top of the soil will help insulate and protect the roots. Any kind of mulch will work fine. I personally would avoid using any dyed mulch since it can stain your container, but pine straw, hardwood, or bark mulch are all good choices. If you can find pine straw that would be my first choice since as it breaks down it can help acidify the soil, which is very important when growing blueberries. If possible, move your containers up close to the house where they will benefit from the radiant heat; this will also help protect them from harsh winds. You will want to avoid fertilizing during the winter months but you may need to hand water if they are under cover and Mother Nature cannot reach them when it snows or rains. Even though the plants go dormant we do not want the roots to completely dry out. Make sure the drain holes are not clogged so that excess moisture can freely drain out of the container. Too much moisture that is not able to drain can freeze and damage the roots. Another option would be to bury the actual pots in the ground and take them out next spring. As for your raspberries, treat them the same way but keep in mind that they have a more aggressive root system and tend to sucker, so if they live their entire life in a container you may need to root prune in the future.