Can a Rosemary Plant Survive Winter? Tips for Protecting Your Herbs

Rosemary is a popular herb grown in many home gardens. With its pine-like fragrance and flavor rosemary has culinary and ornamental uses. However this Mediterranean native can be particular about its growing conditions, especially when it comes to winter temperatures. So can a rosemary plant survive winter in your garden?

The answer depends on your winter conditions and the variety of rosemary you are growing. With some cold protection methods, you can help rosemary make it through the winter in colder climates. Let’s look at how hardy rosemary plants are and what you can do to improve their winter survival odds.

How Cold Hardy is Rosemary?

Rosemary plants are not very cold tolerant, Most varieties start to suffer damage when temperatures drop below 20°F (-7°C) Prolonged freezing temperatures below 15°F (-9°C) may kill the plants entirely

There are a few rosemary varieties bred to be more cold hardy, surviving temps down to -10°F (-23°C) in USDA zones 6 or 7. But in general, rosemary does best in zones 8-10 where winter lows stay above 10°F (-12°C).

Freezing damage shows up first on the thin leaf tips and edges. Entire leaves or branches may turn brown and crispy under extreme cold. Frost-burned plants are more prone to disease and decline in the following season.

Rosemary grown as an annual plant in colder zones rarely survives the winter. You’ll have the best success overwintering rosemary in zones 7 or warmer. Further north, you’ll need to bring potted rosemary plants indoors before winter.

site:gardeningknowhow.com Winter Protection for Rosemary

Protecting rosemary for winter depends on your climate conditions. Here are tips to improve rosemary’s cold tolerance in different situations:

In Zone 8 or Warmer

• Plant rosemary in a sheltered spot, protected from winter winds. Near a south-facing wall is ideal.

• Prune plants back by a third after the first fall frost.

• Mound mulch, chopped leaves, or compost around the base to insulate roots. 4-6 inches is sufficient.

• Surround plants with landscape blocks or bundles of twigs to hold mulch in place.

• Drape plants with frost blanket or burlap if hard freeze is forecast. Remove coverings during the day.

In Zone 7 or Colder

• Grow rosemary in containers that can be moved indoors for winter.

• Before first frost, prune plants by half and bring inside to a sunny window.

• Water sparingly over winter, just enough to prevent leaves from shriveling.

• Move plants outside after the last spring frost date. Harden off in shade for a week before full sun exposure.

With a Cold Hardy Variety

• Choose a rosemary variety rated for zone 6 or colder, like ‘Arp’ or ‘Madeline Hill’.

• Plant in spring to establish roots before winter. Mulch well in fall.

• Try overwintering in a cold frame or unheated greenhouse if possible.

• Expect some winter dieback. Prune out dead sections in spring.

site:greenupside.com Ideal Temperature Range for Rosemary

While rosemary can survive brief light frosts, extended cold below its preferred temperature range will damage the plants. Here are the effects of various temperatures on rosemary:

• Below 10°F (-12°C) – Most varieties killed.

• 10-20°F (-12° to -7°C) – Damage likely unless hardened off.

• 20-30°F (-7° to -1°C) – Tolerable for short periods.

• 30-40°F (-1° to 4°C) – Chilly but safe for mature plants.

• 40-50°F (4° to 10°C) – Preferred nighttime winter minimum.

• 50-60°F (10° to 16°C) – Cool end of preferred daytime range.

• 60-65°F (16° to 18°C) – Ideal daytime temperature for winter.

• 65-75°F (18° to 24°C) – Perfect for seed starting.

• 75-80°F (24° to 27°C) – Upper limit for active growth.

Rosemary does best where winter lows remain above 20°F (-7°C), and daytime highs reach 60-65°F (16-18°C) even in the coldest months. Morning frosts are tolerable if day length warming follows.

How to Help Rosemary Survive Winter

If winter temperatures in your area drop below rosemary’s comfort zone, you can take steps to improve the odds your plants will make it through the cold season:

Choose a Sheltered Site

A warm microclimate is key to overwintering tender herbs like rosemary. Plant it in a south-facing spot, protected from wind. Near a heat-radiating wall or rock retaining wall is ideal.

Provide Winter Insulation

Mulch heavily around the base with shredded leaves, pine straw, or chopped bark. Mounding the mulch up the stems provides even more insulation.

Try Season Extenders

Cloches, cold frames, mini-hoop tunnels, and other covers trap heat while protecting from frost. Ventilate on sunny days to prevent overheating.

Grow in Containers

Potted rosemary is easier to shelter in a garage or unheated entryway when hard freezes strike. Move the plants indoors for the winter season.

Choose Cold Hardy Varieties

Select rosemary varieties rated for colder zones like ‘Madeline Hill’ and ‘Arp’. While not bulletproof, they have better odds than less hardy types.

Prune Conservatively

Avoid severe pruning in fall. Leave more top growth to protect the crown. Prune back dead sections in spring as needed.

Overwintering Potted Rosemary

If you grow rosemary in containers, you can move the plants to shelter for winter once nighttime temperatures drop into the 30s Fahrenheit. A sunny window indoors is a good spot. Here are tips for overwintering potted rosemary:

• Bring plants inside before the first fall frost.

• Prune lightly to reduce top growth and water needs.

• Water just enough to keep soil slightly moist, not soggy wet.

• Provide as much sunlight as possible. Supplement with grow lights.

• Watch for pests like aphids, scale, and spider mites. Treat promptly.

• Move rosemary back outside after the last spring frost.

• Harden off plants in shade for 7-10 days before placing in full sun.

The keys to happy indoor rosemary are bright light, minimal watering, and good air circulation. A heated garage or enclosed porch also works if sunlight is abundant. With attention to its needs, potted rosemary should sail through winter and regrow vigorously in spring.

Is Rosemary Worth Overwintering?

For many gardeners, deciding whether to overwinter rosemary will depend on how readily available and affordable plants are in your area.

If rosemary is cheap and easy to find locally, it may be easier to treat it as an annual and replant each spring. But if rosemary is expensive or hard to find, overwintering makes more economic sense.

Overwintering also helps develop fuller, more robust rosemary plants over years. Older plants have more developed flavors and oil concentrations in the leaves.

If you use rosemary frequently for cooking or herb crafts, keeping plants alive through winter is worthwhile. You’ll have a handy source of fresh rosemary year-round.

While rosemary prefers warm conditions, the plants can successfully overwinter in colder climates given proper care. Key factors for winter survival include:

• Selecting sheltered garden sites with warmer microclimates.

• Securing winter mulch to insulate plant crowns from hard freezes.

• Using season extending structures to trap additional daytime heat.

• Growing rosemary in containers that can be moved indoors as needed.

• Choosing rosemary varieties rated for colder winter zones.

• Avoiding late fall pruning that limits the plant’s own cold protection.

With one or more of these strategies in place, your rosemary should be ready for old man winter when he comes knocking. The reward will be fresh rosemary all season long to flavor your cooking.