Can Rosemary Survive a Freeze? | Hardiness, Protection & Overwintering

Rosemary can survive a light frost or mild freeze, but a hard freeze below 20°F typically damages or kills the plant unless it’s a cold-hardy cultivar, well-mulched, or moved to shelter.

The question isn’t whether rosemary might survive freezing weather—it’s what kind of freeze and where you’re growing it. A 28°F frost that hits overnight and melts by morning is different from a week-long deep freeze in single digits. The difference between life and death comes down to your USDA zone, the cultivar you planted, and whether you’re willing to take a few simple steps before winter arrives.

How Cold Can Rosemary Tolerate?

Rosemary is generally considered hardy in USDA Zones 7 through 10, according to Michigan State University Extension. In those warmer zones, the plant routinely survives winter outdoors without special treatment. The trouble starts south of Zone 7—Illinois Extension notes that rosemary is “not reliably hardy” in Zone 6 or colder and recommends bringing it indoors for winter. The approximate survival floor for most common rosemary varieties is around 10°F, though some cold-hardy cultivars like ‘Arp’ may briefly survive temperatures as low as 0°F in a protected microclimate.

What Freezing Temperatures Actually Do to Rosemary

When temperatures drop below freezing, the water inside rosemary’s leaves and stems freezes, expanding and rupturing the cell walls. A light frost might only damage the most exposed leaves—those turn brown and drop—while the main plant survives. A hard freeze, especially when it’s paired with wet soil and repeated thaw-and-refreeze cycles, often kills the entire root system. The single worst combination is frozen ground that heaves the roots upward, exposing them to drying air, a problem A Way To Garden identifies as frost heaving. Rosemary in wet soil during winter is especially vulnerable because waterlogged roots freeze solid and rot when they thaw.

Can Rosemary Survive a Freeze Outdoors?

The honest answer depends on three factors: your USDA zone, the specific cultivar, and the severity of the freeze.

• Zones 7–10: Rosemary survives outdoor winter freezes with only moderate protection or none at all.
• Zone 6: The odds are low without a cold-hardy cultivar plus heavy mulching and a sheltered location. Expect losses most winters.
• Zone 5 and colder: Outdoor survival is rare even with protection. Plan to overwinter indoors or take cuttings.

Colorado State Extension notes that some rosemary cultivars are described as “Zone 6 hardy,” meaning they may survive near 0°F in a good year. But for most common supermarket rosemary plants, anything below 20°F is life-threatening.

How to Protect Rosemary Through Winter (Step by Step)

The key to overwintering rosemary is preventing root damage and avoiding the wet-cold combination that kills more plants than the cold alone. These steps from extension services and experienced gardeners cover both in-ground and container plants.

In-Ground Plants: Zones 6–7 (Borderline Climates)

• Choose a well-drained spot with at least six hours of daily sun. Southern exposure near a wall that radiates heat at night is ideal.
• After the first frost, apply a 3- to 6-inch layer of organic mulch—straw, shredded leaves, or pine bark—around the base. Do not bury the crown.
• Cover the plant with a frost blanket, row cover, or an overturned cardboard box when temperatures are expected to dip below 20°F. Remove it during the day if temperatures rise above freezing.
• Do not let plastic sheeting touch the foliage. A YouTube gardening demonstration from the You Can Grow It group warns that plastic in direct contact with leaves can freeze them on contact.
• Brush snow off the branches during heavy storms to reduce breakage and cold stress, as Plant Addicts advises.

Container Plants: Move to Shelter When Temperatures Hit the Low 20s

A Way To Garden recommends moving potted rosemary to a garage, shed, or cool porch when nighttime temperatures settle into the low 20s°F. The plant needs light but does not need to be in a warm room. A cool window in an unheated room is better than a warm living room. Water sparingly—let the soil dry out between waterings. Rosemary is prone to root rot in wet winter soil, and that risk is higher in a pot than in the ground.

What to Do If a Freeze Is Coming Tonight

A quick freeze warning doesn’t give you time to dig or re-pot, but you can still take immediate action.

How to Bring Rosemary Indoors for Winter

For gardeners in Zone 6 and colder, the most dependable method is to move rosemary indoors before the first hard frost. Southern Living advises doing this while temperatures are still above freezing and disturbing the roots as little as possible.

• Place rosemary in a south-facing window or under a grow light for at least six hours daily.
• Keep the plant in a cool location—around 50–60°F if possible—rather than a warm room. Warm, dry indoor air stresses rosemary more than cool indoor air.
• Water sparingly. Let the top inch of soil dry before watering again. Overwatering indoors during winter is the most common way to kill a rosemary plant.

Propagating Cuttings as a Backup Plan

If your rosemary plant is too large to move, or if you simply want insurance against a hard winter, take cuttings before the ground freezes. Southern Living recommends cutting 4- to 6-inch lengths from green, not woody, growth. Strip the lower leaves and place the cuttings in water or moist potting mix. Roots typically form in four to six weeks. A few rooted cuttings in small pots on a cool windowsill cost almost nothing and can replace a full-size plant in spring.

Common Mistakes That Kill Rosemary in Winter

• Overwatering: Wet roots in cold soil is a death sentence. Rosemary prefers dry feet in winter.
• Planting in a low spot: Cold air sinks, and frost settles in low ground. Raised beds or slopes drain better and stay warmer.
• Assuming all rosemary is the same hardy: A supermarket rosemary plant bought in summer is usually a tender variety that will not survive a freeze. If you want perennial rosemary outdoors in a borderline zone, buy ‘Arp’ or another named cold-hardy cultivar.
• Bringing rosemary straight into a warm house: The shock of moving from 30°F outdoors to 70°F indoors can kill leaves within days. Acclimate the plant in a cool room or unheated porch for a week first.

How to Tell If Rosemary Survived a Freeze

Wait until the weather warms above freezing for several days. Then check for these signs.