If you grow lavender (Lavandula spp.) in your garden, you're familiar with its heady fragrance and attractive features as a garden perennial. Several types grow in a home garden, including English lavender (Lavandula angustifolia) and lavandin (Lavandula x intermedia), which is sometimes called French lavender; both grow in U.S. Department of Agriculture plant hardiness zones 5 through 8.. Spanish lavender (Lavandula stoechas) is better suited to warmer areas and grows in USDA zones 6 through 9. Although all are tough plants that usually survive winter in their growing zones, a little extra care in fall can help lavender put out lots of healthy new growth in spring.
Pruning in Preparation
Whatever type of lavender you grow, don't prune it heavily late in the season. The best time to trim the plant and cut back dead stems is in spring, after you see its first flush of new growth. Then harvest stems for their fragrant foliage and flowers from late spring through the midsummer months, but stop harvesting in late August or early September.
Once harvesting is done, you can leave the plant uncut for the winter. But if you experience heavy winter snow, you can minimize snow damage by shearing the plants into mounds in late summer, provided you only cut back younger stems and avoid cutting into old wood, because this promotes tender young growth that's easily damaged by cold.
When trimming lavender, use sharp shears that won't tear the stems and wipe your blades with rubbing alcohol between each cut to prevent spread of plant disease.
Providing Winter Protection
If you live where subfreezing winter temperatures are common, it's helpful to cover your lavender plants with evergreen boughs once you've had your first frost and the ground is cold. The boughs shade the plants and prevent heaving of the plants out of the ground during freeze-thaw cycles. The covering also provides protection from cold winter winds that can dry out the plants and cause die-back of stems.
Protecting Potted Lavender
Lavender plants also perform well when container-grown, and winter needn't mean the end of them. If you live within their outdoor growing range, sink the pot into the ground near a warm building wall, with soil at the same level as in the pot. The garden soil helps insulate the roots, but you can also add some shredded bark as mulch under the plant for further protection. Avoid any winter pruning, reserving this for the following spring.
If putting the pot into the ground isn't convenient, move it near a wall and bury the pot in dry leaves to protect it from cold, or set it into a larger pot with leaves or mulch filling the space between the two pots. If the soil becomes dry but isn't frozen during winter, give the plant a light watering now and then.
You can also take a potted lavender indoors for the winter, keeping it in a sunny window, but water it lightly only every week or two while it's resting. This also works well if you live outside your plant's growing range and your winter temperatures are too cold to keep the pot outdoors.