French lavender (Lavandula dentata) is technically classified as a woody perennial sub-shrub, meaning it develops a permanent woody base that survives from year to year. Its ability to live past a single season, however, depends entirely on the winter climate where it is planted. While it maintains foliage year-round in warmer locations, gardeners in regions with cold winters must often treat this Mediterranean native as a seasonal annual. This plant requires specific conditions to ensure its longevity and return each spring.
Defining the Perennial Status of French Lavender
The longevity of French lavender is best understood using the United States Department of Agriculture (USDA) Hardiness Zone system. As a woody sub-shrub, Lavandula dentata is reliably perennial only in the warmest zones, typically thriving in Zones 8 through 11. In this range, the woody stems do not die back during winter, allowing the plant to develop into a mature shrub. Outside of these areas, French lavender is considered a tender perennial because it cannot survive the average winter temperatures of colder zones. If winter temperatures consistently drop below freezing, the plant will not survive outdoors without special protection.
Geographic Limits and Overwintering Care
The primary threat to French lavender’s perennial status is cold. Sustained temperatures below 20°F (-6°C) often prove fatal to the roots and woody structure. Even a light frost of 32°F (0°C) can cause significant dieback on the foliage and tender new growth. Gardeners in Zones 7 and colder must take proactive measures to ensure the plant returns the following spring.
Container Overwintering
Growing the plant in a container allows it to be moved indoors for winter protection. When transitioning the plant, place it in a cool location, ideally between 40°F and 65°F (5°C to 18°C), such as an unheated garage or a bright, cool basement. The plant should receive some light, even if supplemental. Watering should be minimal, only occurring after the top inch of soil has dried completely to prevent root rot.
For plants remaining in the ground in marginal zones, heavy mulching provides a degree of root insulation. Apply a two-to-three-inch layer of organic material, such as straw or wood chips, around the base of the plant once the ground begins to freeze. This mulch must be kept a few inches away from the plant’s crown to prevent moisture accumulation and rotting the main stem. Furthermore, avoid heavy pruning in the late fall, as the resulting tender new growth will not have time to harden before the cold arrives.
Essential Care for Perennial Success
The long-term health of French lavender depends on providing optimal growing conditions during the active season. The plant requires at least six to eight hours of direct, full sunlight daily to maintain vigor and promote dense growth. Insufficient light leads to a weak, leggy plant that is more vulnerable to disease and cold.
Soil drainage is arguably the most important factor for perennial lavender success, especially since the plant is native to dry, rocky Mediterranean regions. It must be planted in sandy, gravelly, or extremely well-draining soil, as it quickly succumbs to root rot in heavy, waterlogged conditions. Once established, the shrub is drought-tolerant and requires very little supplemental watering, which should be done sparingly even during dry spells.
Proper pruning encourages new growth and is essential for preventing the plant from becoming excessively woody and sparse. French lavender should be lightly pruned throughout its long blooming season to remove spent flowers and maintain a dense, mounded shape. The more substantial annual pruning should occur in late summer or early fall, where you should remove approximately one-third of the green, leafy growth. A cardinal rule for all perennial lavenders is never to cut into the old, brown, woody stems, as this specific species will not regenerate growth from that dead wood.