Hello. I am wondering what to do with my raised lavender bed in the winter. I just started it this summer so some of the plants are quick small/young. I fear the soil (about a foot in depth) will freeze solid in the winter and kill everything. Would putting it in the garage (unheated) by a window suffice or do I need to bring the whole thing inside? Thank you for your time.
Dear gardener,
Thank you for your great question. Luckily, similar questions have been asked in the past and I think you will find the answers useful. See below.
Lavender (Lavandula angustifolia) comes in a number of different varieties, and some are hardier than others. I am hoping that you got your plants at a local nursery, which is usually a reasonable guarantee that your plants will be hardy for our growing area and can be overwintered in a garden bed or a container.
In general, for lavender to over winter in a container, you need a large container with a goodly amount of soil since more soil offers more insulation. It also needs protection against the wind (e.g. with a burlap shield). You should also mulch the top of your soil (e.g., with bark mulch or leaves) to provide a layer of freezing protection. Thirdly, lavender will need light during the winter.
However, the issues that you have raised in your question incline me to agree with you that perhaps you may not be able to insulate your lavender plants adequately in this particular container. As you suggested, there is not enough soil in your container to provide reasonable insulation. I am also a bit concerned about the high legs on the container since they will also make it difficult to insulate the plants. Thirdly, you ask if putting the container in your garage would work. It might be a reasonable option since the plants will be better protected but I am still not sure if the window will provide enough light, or if the temperature is adequate.
Maybe a good option would be to repot your lavender into a container that you can bring indoors for the winter. There is information on overwintering lavender indoors in a container in a previous Toronto Master Gardeners post:
Make sure that you keep it in a cooler room, with lots of light, and away from drafty windows. As the lavender plant will not be actively growing during the winter, keep your watering to a minimum –letting it dry out between waterings – and do not fertilize until growth starts again in the spring.
A different past post explains how to acclimatize your lavender (and other plants that you bring inside) to being indoors for the winter:
Before the first frost, start to acclimatize the plant to its new (less sunny) indoor environment, by moving it inside for a couple of hours daily for a week – increase the time it spends indoors gradually. Start to water less frequently than you’ve done throughout the summer.
Some guidelines with numbers have been provided in a previous Toronto Master Gardener question. The temperature and light requirements for overwintering lavender will help you make a decision whether your garage will keep your plants alive over the winter.
Temperature: Keep the pot in a cool room, away from drafts. The plant can tolerate a nighttime temperature as low as 5 degrees C (40 degrees F) and warm daytime temperature up to 18 degrees C (65 degrees F). Keep the plant away from heaters.
Water: The lavender will not be actively growing over the winter, so do not water it often and let the top 2.5 cm (1 inch) of soil dry out between waterings. Too much watering risks root rot.
Light: As noted above, the lavender needs lots of light – try to keep it in a bright spot on the windowsill. If the plant does not do well, a grow light would help supplement the natural light.
Space: Give the plant lots of space so that air circulates well around it.
Soil: The soil should be well-draining.
Fertilize: Do not fertilize over the winter. Only fertilize once it starts showing signs of growth in the spring.
As a final comment: One of the main concerns in overwintering your lavender is to ensure that it gets enough light indoors. It is nearly inevitable that your lavender plants will probably look quite sad and spindly over the winter, but they should start to revive come spring.
For further information please check the following links
https://www.torontomastergardeners.ca/askagardener/munstead-lavendar/
https://www.torontomastergardeners.ca/askagardener/overwintering-english-lavender/
https://www.torontomastergardeners.ca/askagardener/overwintering-container-lavender/#