Harsh winters are not merciful to lavender. Even if the plant is dormant at that time, adverse conditions can threaten its survival. Some factors such as lack of pruning or excessive pruning can make it more vulnerable to inclement weather. Between low temperatures and constantly wet soil, the crown of the grass turns gray and the stems woody. To all appearances, it appears lifeless, and unless protected from the elements, it may not come back to life.
To check for signs of life in the woody crown, cut off one of the stems. If the stem is green and does not break easily, and the leaves are fragrant, you can nurse it back to health. To revive a late-stage lavender, transplant it into a pot and bring it indoors. With light, temperature, and humidity set at optimal levels, water just enough to keep the soil slightly moist. Then in spring it will show the first signs of growth.