Lavender is a fragrant, silvery-green herb prized for its beauty and calming scent. As a Mediterranean native, it requires specific climate conditions to thrive. The single greatest factor determining lavender’s success is the temperature and climate of its planting location. Understanding the temperature range a lavender plant can tolerate is paramount to successful, long-term gardening. Planting lavender outside its preferred growing zone often leads to plant loss.
Understanding USDA Hardiness Zones
The United States Department of Agriculture (USDA) Plant Hardiness Zone Map guides gardeners on plant survival across North America. This map divides the continent into zones based on the average annual extreme minimum winter temperature. Each zone represents a 10-degree Fahrenheit difference, and zones are subdivided into ‘a’ and ‘b’ sections reflecting a 5-degree difference.
The zone number indicates the coldest temperature a perennial plant can survive. For example, a plant hardy to Zone 5 can tolerate significantly colder winter temperatures than one hardy only to Zone 8. This system is an invaluable tool for selecting perennial plants. However, the zones do not account for other factors like summer heat, soil type, or humidity, which also impact a plant’s health.
General Zone Requirements for Lavender
Most commonly grown lavender varieties require a growing range spanning from USDA Zone 5 through Zone 9. This range means the plant tolerates minimum winter temperatures between -20°F and 30°F, depending on the specific cultivar. A primary requirement for survival is sufficient winter cold to induce a dormancy period necessary for long-term health.
The upper limit, typically Zone 9, is determined by the plant’s need for a hot, dry climate, not cold tolerance. Lavender is native to the Mediterranean region, thriving in full sun and low humidity. In very warm zones with high humidity, the plant struggles and is prone to fungal diseases and root rot.
Matching Specific Lavender Varieties to Your Zone
The general zone range of 5 to 9 becomes more specific when considering the three main types of lavender species.
English Lavender
English Lavender (Lavandula angustifolia) is the most cold-tolerant, reliably surviving in USDA Zones 5 through 9. This species is favored by northern gardeners because its superior hardiness allows it to survive colder winters than other varieties.
Lavandin
Lavandin (Lavandula x intermedia), a hybrid of English and Portuguese lavender, is slightly less cold-hardy and recommended for Zones 6 through 9. Lavandin plants are typically larger and produce a strong, camphor-scented oil, making them popular for commercial production. The hybrid variety ‘Phenomenal’ is noted for its tolerance of both cold winters and higher heat and humidity.
Spanish and French Lavender
Spanish Lavender (Lavandula stoechas) and French Lavender (Lavandula dentata) are the least cold-hardy. They thrive best in the mild-winter climates of Zones 7 or 8 through 10. Spanish lavender is recognizable by its unique flowers topped with colorful bracts, but it will not survive temperatures below Zone 6. Gardeners in these warmer zones benefit from the heat and drought tolerance of these species, which can also handle slightly more humidity than English varieties.
Ensuring Lavender Thrives: Soil and Climate Management
Survival within the correct hardiness zone depends heavily on managing the growing environment. Lavender must be planted in soil that drains exceptionally well, as root rot is a common killer, especially during cold, damp winter months. If the native soil is heavy clay, amending it with sand or grit, or planting in a raised bed, is necessary to prevent standing water around the roots.
The plant requires a minimum of six hours of direct sun daily to maintain vigorous growth and produce fragrant oils. In borderline cold climates like Zone 5, gardeners can increase the plant’s chance of survival by applying a loose winter mulch of evergreen boughs or straw. This protective layer helps insulate the plant’s crown from extreme freezing temperatures and fluctuating freeze-thaw cycles. Providing excellent air circulation is also beneficial, particularly in humid regions, to keep the foliage dry and reduce the risk of fungal disease.