An ornamental herb, lavender is an evergreen plant that grows well in most climates. The plants tolerate both heat and severe cold. While most lavender plants survive well without winterisation, a few winter precautions help keep the plants looking their best.
An increased mulch layer helps insulate the soil, which protects the lavender roots from winter cold. Apply up to 3 inches of mulch over the soil around the plants. Mulch also prevents frost heave, which occurs when the soil shifts because of freeze and thaw cycles in winter. Frost heave can uproot or break plant roots. The mulch helps regulate the soil temperature so its protected from the danger of heaving.
Lavender is a hardy plant but winter winds can damage the branches and foliage. The dry, cold winds wick moisture from the lavender's evergreen leaves, which causes burning or foliage death. High winds can break the branches, especially when they are frozen. Plant the lavender in an area protected from winter winds or erect a windbreak around the bush in early winter. Wrap burlap around two stakes on the windward side of the plant for a quick yet inexpensive windbreak.
Move the containerised lavender to a protected area in late fall or early winter. You don't need to bring the plants inside, but place them in an area protected from heavy winds. While plants grown in beds rarely require winter watering, the soil in containers may dry out too much and damage the lavender. Water the soil sparingly when the temperatures are above freezing. Supply just enough moisture in winter to prevent the soil from drying out completely.
Lavender may require a cleanup pruning in early spring to remove any winter damage. Prune before new growth begins on the plant but after most frost danger is past. Cut out any damaged stems or branches, removing them at their base. While summer pruning is also beneficial to lavender, don't prune lavender plants any later than early September. Pruning encourages new growth on the plants, so a late pruning causes tender new shoots to form that are more prone to winter freeze damage.