How does frost affect different lavender varieties?

Frost and freezing temperatures affect different lavender varieties quite differently, primarily due to their varying levels of cold hardiness. Lavender species originate from diverse climates, leading to distinct tolerances.

Here's a breakdown by common lavender types:

1. English Lavender (Lavandula angustifolia) - The Cold-Hardy Champion

• Hardiness Zones: USDA Zones 5-9. Many cultivars can reliably survive outdoor winters down to -10°F to -20°F (-23°C to -29°C), and some specific ones like 'Munstead' are even noted for Zone 3 with proper protection.

• How Frost Affects Them:

  • Resilience: This is by far the most cold-hardy lavender species. Its woody stems and dense growth habit offer natural insulation.

  • Winter Appearance: In cold climates, English lavender typically remains semi-evergreen. Its foliage might turn a duller grayish-green or brownish, or even take on a slightly purplish tint during the coldest months, but the plant's core structure remains alive.

  • Dieback: In very harsh winters or if not fully established, some top growth may experience dieback (turn brown and brittle), but the woody crown and roots usually survive to re-sprout in spring.

  • Key Cultivars for Cold: 'Munstead', 'Hidcote' (also 'Hidcote Pink'), 'Phenomenal' (a lavandin hybrid, but often marketed for exceptional cold hardiness down to Zone 4), 'Royal Velvet', 'Blue Cushion'.

• Protection in Cold Zones: While hardy, in Zones 3-5, a layer of well-draining mulch (like gravel or pine needles, not moisture-retaining wood chips) around the base can help insulate the roots. Good snow cover acts as excellent natural insulation. Ensuring superb drainage is paramount, as wet, cold soil is more damaging than cold temperatures alone.

2. Lavandin Hybrids (Lavandula x intermedia) - Good Hardiness, Often More Robust

• Hardiness Zones: USDA Zones 5-9, generally hardy to around -10°F (-23°C). They are often slightly less cold-hardy than the most robust English lavenders but more adaptable to various conditions.

• How Frost Affects Them:

  • Vigor: These are vigorous, larger plants. While hardy, their larger size can sometimes make them slightly more susceptible to wind desiccation in very exposed, cold locations.

  • Dieback: Similar to English lavender, they may experience some top dieback in colder zones, but the root crown typically survives.

  • Winter Appearance: Generally semi-evergreen.

  • Key Cultivars: 'Grosso', 'Provence', 'Abrialii', and 'Phenomenal' (though often grouped with English for hardiness, it's technically a lavandin hybrid). 'Phenomenal' is particularly noted for its cold hardiness and disease resistance.

• Protection: Similar protection strategies as English lavender apply.

3. French Lavender (Lavandula dentata) - Tender to Frost

• Hardiness Zones: USDA Zones 8-10. These are much less cold-hardy.

• How Frost Affects Them:

  • Significant Damage: French lavender will quickly suffer frost damage, turn brown, and likely die if exposed to prolonged freezing temperatures below 20-25°F (-4°C to -7°C), especially if not well-established or protected.

  • Winter Appearance: If not killed, foliage will brown and become brittle.

• Protection: In zones colder than 8, French lavender is typically grown as an annual, enjoyed for one season and then replaced. Alternatively, it can be grown in containers and brought indoors to a bright, cool (but frost-free) location for the winter, acting as a tender perennial or houseplant.

4. Spanish Lavender (Lavandula stoechas) - Most Tender

• Hardiness Zones: USDA Zones 7-10. This is generally the least cold-hardy of the commonly grown lavenders.

• How Frost Affects Them:

  • Very Sensitive: Highly susceptible to frost damage. Temperatures consistently below 20°F (-7°C) are often fatal.

  • Damage: Foliage will quickly turn black or brown and die off.

• Protection: Like French lavender, Spanish lavender is best grown as an annual in colder climates or in containers that can be moved indoors for winter protection. Even in Zone 7, it may require significant mulching and a sheltered location to survive.

General Frost Protection Tips for All Lavenders:

Regardless of variety, a few universal principles help lavender survive colder temperatures:

• Excellent Drainage: This is the absolute most critical factor. Wet, soggy soil in winter is a death sentence for any lavender. Amend heavy soils with plenty of grit.

• Full Sun: Ensures the plant is healthy and robust going into winter.

• Good Air Circulation: Helps prevent fungal issues, especially when snow melts or in humid winter conditions.

• No Late-Season Fertilizing: Avoid fertilizing in late summer or fall, as this encourages tender new growth that will be easily damaged by frost.

• Proper Pruning: Prune in spring after the last frost, or lightly after the first flush of blooms. Avoid heavy pruning in late fall (within 6 weeks of the first expected frost), as it can stimulate new growth vulnerable to cold.

• Mulching (Type Matters): For cold-hardy varieties, a 2-3 inch layer of inorganic mulch like pea gravel or small stones around the base can insulate roots while preventing moisture buildup. Avoid organic mulches (wood chips, straw) if they hold too much moisture.

By understanding the specific hardiness of each lavender type and applying appropriate care, gardeners can successfully grow lavender in a wide range of climates.

Lavender Farm in Door County Wisconsin. You can buy lavender products online at islandlavender.com