I have a raised wood flower bed (lined on the inside with garden fabric). In it I have planted lavender, blanket flower and seedum. Im not sure how to prepare this container for winter…Should i cut back the flowers? Should i wrap the sides or top of the container in burlap. This is the first winter for the plants. Im in zone 5….near toronto. This planter is mostly sun…shade late afternoon. The potting soil stays most…and i rarely water the plants as my moisture meter always reads moist/wet. Please help!
Essentially, you are growing these plants, which should be hardy over winter in Zone 5 (although it does depend on which type of lavender) in a large container. There is no need to cut them back and it would certainly be the wrong thing to do to the lavender.
To overwinter the plants successfully, you need to keep them dormant. A plant growing in the ground is more protected from alternate freezing and thawing than one in a container. Here are some tips, which will apply also to the hostas and other plants I see that you have in large pots:
- The ideal solution is to move the plants into the ground where their roots will be more protected. If you have flower or vegetable bed into which they can be moved for the winter, dig up your plants and replant them there. Bring them back to the planters and pots in spring.
- If you are not moving the plants, water thoroughly right before the ground freezes, (but after a few hard frosts) to provide a supply of water the plants can use when the soil thaws. Mulch with leaves and, over the winter, add some snow on top to add insulation and to provide water during thaws.
- Group the potted plants together in a sheltered spot and bank some insulating material, such as straw, around them. as well as the leaf and snow topping. You could also move them into an unheated garage or shed.
- On the other hand, perennials in containers often get too much water throughout the winter season, since a thaw may not reach the drainage holes, and roots can end up sitting in water and then ice. (I am a bit concerned about the drainage in your planter, since you say it is always moist despite the very dry summer we’ve had.) To get around this issue, erect some kind of raised cover so they won’t receive excess rain/snow.
- In the spring, cut back the dead stems and leaves (but NOT the lavender) and wait for signs of life before moving the plants back into the planters and pots.
For specifics on managing the lavender, see a previous answer we gave another inquirer here. For general information on growing plants in containers, see this article we prepared for the organization Toronto Balconies Bloom here.
Good luck overwintering your plants!