Lavender (especially Lavandula angustifolia, or English lavender) is known for its resilience, but it does have preferred temperature ranges and specific tolerances that help it thrive. Being a Mediterranean plant, it generally loves sun and heat but also has good cold hardiness in many varieties.
Here's a breakdown of the temperature ranges lavender can tolerate:
Ideal Growing Temperatures:
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Optimal Daytime: 68-95°F (20-35°C) is often cited as the preferred range for active growth and blooming.
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Optimal Soil Temperature: Above 65°F (18°C) favors growth and regeneration after harvest.
Cold Tolerance:
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Most lavender cultivars are hardy in USDA Zones 5-9.
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Cold-Hardy Varieties: English lavenders like 'Munstead', 'Hidcote Blue', and 'Phenomenal' (a lavandin hybrid) are particularly cold-tolerant and can survive winter temperatures down to -10°F to -20°F (-23°C to -29°C), sometimes even Zone 3 with proper protection.
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Winter Protection: In colder zones (USDA Zone 4 and below), lavender may benefit from winter protection like mulching, or being grown in containers that can be brought indoors. In these very cold climates, the softer, non-woody parts of the plant may die back, but the woody core can re-sprout in spring.
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Frost Sensitivity: Young lavender plants are more sensitive to frost. It's best to plant them outdoors after all danger of frost has passed in spring.
Heat Tolerance:
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Lavender thrives in warm, sunny climates and can generally tolerate summer temperatures up to 95°F (35°C).
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High Heat Stress: When temperatures exceed 95-100°F (35-38°C), especially for prolonged periods or with high humidity, lavender can show signs of stress:
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Leaves may become lighter in color or curl.
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Susceptibility to sunburn.
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In severe cases, wilting or drying.
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Extended bloom periods may stop.
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Heat-Tolerant Varieties: Spanish lavender (Lavandula stoechas), French lavender (Lavandula dentata), and Lavandin hybrids (Lavandula x intermedia such as 'Grosso' or 'Provence', and particularly 'Phenomenal') are generally more heat and drought-tolerant than pure English types. These are often recommended for warmer climates (USDA Zones 9-10).
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Mitigation in Hot Climates: In very hot climates (like Addison, Texas, USDA Zone 8a), providing some afternoon shade, especially during the peak of summer, can help prevent stress and scorching. Ensuring excellent drainage is even more crucial in hot, humid environments to prevent root rot.
Key Factors Beyond Temperature:
While temperature is vital, lavender's overall health and ability to tolerate temperature extremes are heavily influenced by other factors:
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Sunlight: Requires at least 6-8 hours of direct sunlight daily.
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Drainage: Absolutely critical. Lavender hates "wet feet" and will quickly succumb to root rot in poorly drained soil, regardless of temperature. Sandy, gravelly, well-drained soil is ideal.
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Humidity: Prefers low humidity. High humidity, especially combined with heat, can lead to fungal diseases.
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Air Circulation: Good air circulation helps prevent fungal issues.
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Soil pH: Prefers slightly alkaline to neutral soil (pH 6.7 to 7.3).
By selecting the right variety for your climate zone and providing excellent drainage and ample sunlight, lavender can be a remarkably resilient and rewarding plant to grow.
Lavender Farm in Door County Wisconsin. You can buy lavender products online at islandlavender.com