Beyond Hardiness Zones - List of Minimum Cold Tolerances for Herbs

Gardeners often rely on the USDA hardiness zone map to determine which plants will thrive in their climate. While this map offers a valuable starting point, it focuses primarily on a plant's ability to survive winter temperatures. However, for many herbs, both annual and perennial, success hinges not just on surviving winter, but also on their tolerance for cool spring and fall weather.

This list details the minimum cold tolerance of various herbs, both annual and perennial. Understanding these specific needs goes beyond the broad strokes of hardiness zones and can help you create a successful herb garden throughout the growing season. Knowing an herb's cool tolerance allows you to:

Plan your planting schedule: Some herbs prefer cooler temperatures and can be sown earlier in spring or planted for a fall harvest.

Provide winter protection: For herbs that are borderline cold tolerant in your zone, understanding their minimum tolerance can help you decide if winter protection is necessary.

Choose the right varieties: Many herbs offer varieties with improved cold tolerance.

By considering both the USDA hardiness zone and the specific cool tolerance and frost resistance of your chosen herbs, you can create a flourishing and productive herb garden year-round.  

Take a look at this listing of what temperature is too cold for an herb.

Annuals:

• Basil (Ocimum basilicum) & Sweet basil (Ocimum basilicum var. dulce): < 32°F (0°C) - Very sensitive to cold. Best grown as an annual.
• Borage (Borago officinalis): 20°F (-6°C) - Can tolerate light frosts.
• Chamomile (Matricaria recutita): 10°F (-12°C) - Prefers cool weather but won't survive hard freezes.
• Chervil (Anthriscus cerefolium): 20°F (-6°C) - Can tolerate light frosts. May bolt (go to seed) in hot weather.
• Cilantro (Coriandrum sativum): 20°F (-6°C) - Prefers cool weather but won't survive hard freezes.
• Dill (Anethum graveolens): 20°F (-6°C) - Prefers cool weather but won't survive hard freezes.
• Epazote (Dysphania ambrosioides): 25°F (-3°C) - Somewhat cold tolerant.
• Fennel (Foeniculum vulgare): 20°F (-6°C) - Can be grown as a biennial in mild climates.
• Sweet fennel (Foeniculum vulgare var. dulce): Same as fennel (20°F/-6°C).
• Lovage (Levisticum officinale): 0°F (-18°C) - Very cold tolerant. (Biennial)
• Nasturtium (Tropaeolum majus): 20°F (-6°C) - Sensitive to frost, but tolerates light freezes.
• Parsley (Petroselinum crispum): 20°F (-6°C) - Can tolerate light frosts, may need winter protection.  (Biennial)
• Purslane (Portulaca oleracea): Not frost tolerant. Best grown in warm weather.
• Salad burnet (Sanguisorba minor): -5°F (-20°C) - Very cold tolerant.
• Stevia (Stevia rebaudiana): 25°F (-3°C) - Somewhat cold tolerant, best grown as an annual in colder climates.
• Summer savory (Satureja hortensis): 20°F (-6°C) - Somewhat cold tolerant.

Perennials:

• Agrimony (Agrimonia eupatoria): 0°F (-18°C) - Very cold tolerant.
• Angelica (Angelica archangelica): -20°F (-29°C) - Extremely cold tolerant.
• Anise Hyssop (Agastache foeniculum): -10°F (-23°C) - Moderately cold tolerant.
• Arnica (Arnica montana): -30°F (-34°C) - Extremely cold tolerant.
• Bay Laurel (Laurus nobilis): 15°F (-9°C) - Somewhat cold tolerant, may need winter protection in colder zones.
• Bergamot (Monarda didyma): -4°F (-20°C) - Moderately cold tolerant.
• Betony (Stachys officinalis): -4°F (-20°C) - Moderately cold tolerant.
• Borage (Borago officinalis): 20°F (-6°C) - Can tolerate light frosts, but may die back in colder winters. (Tender perennial)
• Catnip (Nepeta cataria): 3°F (-16°C) - Somewhat cold tolerant.
• Chamomile (Roman) (Chamaemelum nobile): 5°F (-15°C) - Somewhat cold tolerant.
• Chives (Allium schoenoprasum): 0°F (-18°C) - Very cold tolerant.
• Comfrey (Symphytum officinale): -20°F (-29°C) - Extremely cold tolerant.
• Dandelion (Taraxacum officinale): -5°F (-20°C) - Very cold tolerant.
• Echinacea (Echinacea purpurea): -30°F (-34°C) - Extremely cold tolerant.
• Fennel (Foeniculum vulgare): 20°F (-6°C) - Often grown as a biennial in colder climates, may not survive harsh winters.
• Feverfew (Tanacetum parthenium): 0°F (-18°C) - Very cold tolerant.
• Figwort (Chinese) (Scrophularia buergeriana): -15°F (-9°C) - Somewhat cold tolerant.
• Ginseng (American) (Panax quinquefolius): -40°F (-40°C) - Extremely cold tolerant.
• Hops (Humulus lupulus): -30°F (-34°C) - Extremely cold tolerant.
• Hyssop (Hyssopus officinalis): -4°F (-20°C) - Moderately cold tolerant.
• Ironweed (Vernonia noveboracensis): -10°F (-23°C) - Moderately cold tolerant.
• Laserwort (Saposhnikovia divaricata): -4°F (-20°C) - Moderately cold tolerant.
• Lavender (Lavandula angustifolia): 5°F (-15°C) - Somewhat cold tolerant, may benefit from winter protection in very cold zones.
• Lemon Balm (Melissa officinalis): 5°F (-15°C) - Somewhat cold tolerant, may die back in colder winters.
• Lovage (Levisticum officinale): 0°F (-18°C) - Very cold tolerant.
• Marjoram (Origanum majorana): 20°F (-6°C) - Less cold tolerant, may need winter protection in colder climates.
• Meadowsweet (Filipendula ulmaria): -40°F (-40°C) - Extremely cold tolerant.
• Mint (Mentha spp.): 4°F (-20°C) - Prefers cool weather but won't survive hard freezes. Consider mulching or bringing indoors in cold climates.
• Motherwort (Leonurus cardiaca): -30°F (-34°C) - Extremely cold tolerant.
• Mugwort (Artemisia vulgaris): -40°F (-40°C) - Extremely cold tolerant.
• Oregano (Greek) (Origanum syriacum): 7°F (-23°C) - Somewhat cold tolerant.
• Oregano (Italian) (Origanum vulgare): 5°F (-15°C) - Somewhat cold tolerant.
• Pennyroyal (Mentha pulegium): 20°F (-6°C) - Less cold tolerant, may not survive harsh winters. Consider winter protection or growing as an annual in colder climates.
• Rosemary (Rosmarinus officinalis): 5°F (-15°C) - Somewhat cold tolerant, can survive mild winters with protection. May need to be brought indoors or heavily mulched in colder zones.
• Rue (Ruta graveolens): 5°F (-15°C) - Somewhat cold tolerant, may require winter protection in very cold climates.
• Saffron Crocus (Crocus sativus): 15°F (-9°C) - Somewhat cold tolerant, but may benefit from winter mulch in colder zones.
• Sage (Salvia officinalis): 5°F (-15°C) - Somewhat cold tolerant, may require winter protection in very cold climates.
• Santolina (Santolina chamaecyparissus): 15°F (-9°C) - Somewhat cold tolerant, may need winter protection in colder zones.
• Scullcap (Scutellaria lateriflora): -4°F (-20°C) - Moderately cold tolerant.
• Soapwort (Saponaria officinalis): -4°F (-20°C) - Moderately cold tolerant.
• Sorrel (garden) (Rumex acetosa): -20°F (-29°C) - Very cold tolerant.
• Tansy (Tanacetum vulgare): -30°F (-34°C) - Extremely cold tolerant.
• Tarragon (Artemisia dracunculus): -4°F (-20°C) - Moderately cold tolerant, may benefit from winter mulch in very cold zones.
• Thyme (common), Thymus vulgaris: 5°F (-15°C) - Somewhat cold tolerant, generally survives winters well.
• Valerian (Valeriana officinalis): 0°F (-18°C) - Very cold tolerant.
• Wooly Lamb's Ear (Stachys byzantina): 4°F (-20°C) - Moderately cold tolerant.
• Wormwood (Artemisia absinthium): 3°F (-16°C) - Moderately cold tolerant.
• Yarrow (Achillea millefolium): 3°F (-16°C) - Very cold tolerant.
• Zaatar (Origanum syriacum): 7°F (-23°C) - Somewhat cold tolerant.

Remember, these are just minimum cold tolerances. Factors like microclimates within your garden, winter wetness, and snow cover can all influence how well an herb actually performs. It's always a good idea to research the specific needs of each herb and consider additional winter protection measures if necessary to improve cold and frost resistance. With a little planning and this handy reference guide, you can choose herbs that will flourish throughout the year. 

Ways to Extend the Growing Season and Protect Plants from Frost & Snow:

There are a couple of things that you can do to help protect your herbs in spring and fall. Check the first and last frost dates for your area, and keep them in mind when restarting your garden in spring or putting it to bed at season's end.  The Old Farmer's Almanac has an interactive page where you can get this information. To use it, all you need is your zip code. 

If you're putting your seedlings out early, use protective measures like cold frames.

Mulching with a 3 to 6 inch layer of organic matter like shredded garden leaves, straw, or wood chips helps insulate the soil, too. *This traps heat, retaining warmth that will protect plant roots if temperatures plummet. When frost or snow is expected, adding a frost cloth or landscaping fabric directly over a mulched bed can provide up to 5°F more frost protection than mulching alone. 

A garden weather station is also a handy tool that can provides real-time data on temperature, humidity, and wind, allowing you to proactively protect your plants from unexpected frost or harsh weather above and beyond what's available in your local weather report. You can set frost alerts and adjust watering schedules based on accurate weather information. Some weather stations even have multiple sensors that can monitor the most vulnerable areas in your landscape.

Understanding your herbs' cold tolerances and taking the right steps early in the spring and fall to protect them can help you conquer your fear of frost.

Happy gardening!