Last Updated on October 8, 2026
How to Overwinter Rosemary (Indoors or Outside)
Rosemary stays hardy outdoors only where winter temperatures stay above about 5°F, per University of Maryland Extension. Where it is not hardy, Penn State Extension says to grow it in a pot and take it indoors 2 to 3 weeks before your first fall frost. Indoors, give it a cool room, the brightest window you have, and water only when the pot is dry. Outside, give it a sheltered, well-drained spot and heavy mulch, and know that single-digit cold often kills it.
Two lines matter. The first is a frost night. My vegetable frost tolerance chart rates rosemary semi-hardy, the same class the Plan My Garden planner gives it: it takes a light freeze, and you cover it when the low will be below 28°F. The second is the winter low. That 5°F line decides whether the plant can stay out at all.
To know when your first fall frost usually comes, look up your frost dates on Plan My Garden by zip code.
Indoors or outside: the two paths
| Leave it outside | Bring it indoors | |
|---|---|---|
| When it fits | Winter lows stay above about 5°F (UMD), or you grow a hardier cultivar and accept the risk | Your winters reach the single digits or colder, which Illinois Extension says is often fatal |
| Where | Full sun, well-drained soil, sheltered from extremes, such as along a sunny south-facing wall of the house (Illinois) | A south-facing window in full sun, or supplemental light, with good air circulation (Penn State) |
| Protection | A heavy layer of mulch at the first frost, plus a small portable cold frame if you have one (Illinois) | A cool room, 45 to 55°F, which UNH Extension has found improves survival |
| Water | Drainage is the job: rosemary does poorly in wet or poorly drained clay soil (Penn State) | Wait until the potting soil is very dry, then water until it drains into the saucer (UNH) |
| Main risk | A cold snap with no snow cover | Low light and the wrong amount of water, which Penn State calls the reasons indoor overwintering can be difficult |
| Best plant | A hardier cultivar such as ‘Arp’ or ‘Madalene Hill’ (Penn State, Illinois) | A plant grown in a pot all season, not one dug from the garden (UNH) |
How to bring rosemary indoors, step by step
- Start with a potted plant. My fall gardening checklist lists rosemary among the herbs you can pot up and bring in. A plant grown in a pot all season is one of the main keys to success. Plants dug out of the garden often do not survive the stress of repotting (UNH Extension), so grow next year’s indoor plant in a pot from the start.
- Use a clay pot. Clay lets the soil dry quickly, which is what rosemary wants.
- Bring it in 2 to 3 weeks before your first fall frost. Until then, cover the pot or carry it in on any night below 28°F, the semi-hardy line on my frost tolerance chart.
- Find a cool, bright spot. Aim for 45 to 55°F in front of a south-facing window. Most homes run too warm and too dry for rosemary, so a sunny basement window is ideal if you have one.
- Add light if the window is not enough. Iowa State University Extension says rosemary may need a full-spectrum LED or fluorescent grow light, on a timer for 12 to 16 hours a day. Long, lanky growth means it needs more light.
- Water only when the pot is very dry. Then water until it drains into the saucer. A plant in a cool room needs water less often.
- Keep air moving. North Carolina State Extension says poor air circulation and high humidity can cause powdery mildew, so do not crowd the pot in with other plants.
- Check the leaves for pests. Thrips, aphids, whiteflies, mealybugs and spider mites can be a problem indoors (Penn State). A heavy stream of water every day or so knocks spider mites off the leaves.
Do not expect much new growth. Rosemary does not do a lot of growing in the low light and cool days of winter, says the Illinois Extension herb guide. The goal is a live plant in spring. My guide to overwintering pepper plants uses the same indoor basics, a sunny south window and careful watering, for peppers.
How to leave rosemary outside over winter
- Know your winter low. About 5°F is the line. Single-digit temperatures are often fatal.
- Pick the warmest spot you have. Illinois Extension suggests a site protected from weather extremes, like a sunny, south-facing wall of your home, with well-drained soil and more than 6 hours of direct sun.
- Mulch at the first frost. Add a heavy layer of mulch then, and a temporary extra layer when extreme lows arrive with no snow on the ground. Snow cover itself insulates the plant.
- Use a cold frame on the worst nights. A small portable cold frame may trap enough solar heat to keep the plant above that critical low. My cold frame tips cover where to put one and venting it on warm days.
- Choose a hardier cultivar. Penn State Extension lists ‘Arp’, ‘Athens Blue Spire’, ‘Madalene Hill’ and ‘Miss Jessop’s Upright’ as hardier, with protection. ‘Hills Hardy’ is another name for ‘Madalene Hill’. Hardier is not a guarantee.
For a fall frost night before the real cold, my guide on how to protect plants from frost walks through covering plants step by step and what to do the morning after.
Root rot, mildew and brown tips
Water is what usually kills overwintered rosemary. NC State calls overwatering the common cause of decline or death, and the root rot it causes can be deadly, especially in pots kept indoors over winter. Rosemary also dries out fast indoors, which browns the leaf tips, but that is not a reason to water more. Browning tips can also be a sign of root rot. So feel the soil first. If it is very dry, water until it drains. If it is not, wait. For powdery mildew, the fix is air, not a spray: give the plant room.
Moving rosemary back outside
Move the pot back outside in spring once the danger of frost has passed. The Plan My Garden planner sets rosemary out 1 to 2 weeks after your last frost. Plant it with room to grow: my rosemary spacing page starts it at 1 per square foot, but Penn State lists a mature plant at 2 to 6 feet tall and wide. If you plan to bring it in again next fall, keep it in its pot. My raised bed herb garden layout shows where it fits with the other herbs.
Quick questions
What temperature is too cold for rosemary?
University of Maryland Extension says rosemary is hardy outdoors only where winter temperatures stay above about 5°F, and Illinois Extension says single-digit temperatures are often fatal. On a fall frost night, my vegetable frost tolerance chart says to cover it when the low will be below 28°F.
Can I dig up rosemary from the garden and bring it inside?
You can try, but UNH Extension says plants dug out of the garden often do not survive the stress of repotting. A plant grown in a pot all season has better odds, so grow next year’s indoor plant in a pot from spring.
How often should I water rosemary indoors in winter?
Only when the potting soil is very dry, and then until water drains into the saucer, as UNH Extension advises. A plant in a cool room needs water less often. North Carolina State Extension calls overwatering the common cause of decline or death.
Does rosemary need a grow light indoors?
Often. Iowa State University Extension says rosemary may need a full-spectrum LED or fluorescent grow light, on a timer for 12 to 16 hours a day, and that long, lanky growth means it needs more light.
What is the most cold-hardy rosemary?
Penn State Extension lists ‘Arp’, ‘Athens Blue Spire’, ‘Madalene Hill’ and ‘Miss Jessop’s Upright’ as hardier cultivars, with protection. Hardier is not a guarantee, so give one a sheltered, well-drained spot and mulch it at the first frost.
Plan where rosemary goes next spring
Decide now where your rosemary goes when it comes back out. Plan My Garden is free to start: enter your zip code and it finds your frost dates, draw your beds, pick rosemary and everything else you want to grow, and it places each plant at square-foot spacing and builds a planting schedule from your frost dates.
Related: Vegetable Frost Tolerance Chart · Overwinter Pepper Plants · How Many Rosemary Plants per Square Foot? · Raised Bed Herb Garden Layout
