Rosemary is a fragrant, perennial, evergreen herb that adds delicious flavor to many recipes. It’s also one of the easiest herbs to grow, and growing herbs like rosemary is a simple way to start saving on your grocery bill (pound for pound, fresh herbs are very expensive). The only downsides of growing rosemary are that it’s a fairly slow grower at first, and it’s not as frost tolerant as other herbs like mint. That means you’ll have to take extra steps to overwinter your rosemary if you live in USDA Plant Hardiness Zone 5 or 6 and colder.
Rosemary will live for years with proper care. Plant this versatile herb and use these tips to overwinter rosemary and keep it thriving.
How to Overwinter Rosemary Outdoors
Before You Start
- If you haven’t bought your outdoor rosemary yet, start by choosing a cold-hardy variety, like ‘Arp’ and ‘Alcalde’ rosemary. These varieties have been bred to withstand colder outdoor temperatures, but will still require some protection if grown in Zone 5.
- Select a planting spot that will provide the herb full sun, meaning at least 6 hours of direct sunlight daily. Next to a south-facing wall is ideal, since not only will it get full sun and shield your rosemary from blistering cold winds, but during winter, heat will radiate off your house wall in the evening, creating a microclimate a few degrees warmer than farther away in your yard.
- Amend the soil before planting rosemary with compost and bonemeal. This will create loose, fertile soil that promotes good drainage and prevents soil compaction. Rosemary is hardy and will tolerate most environmental conditions except soggy soil, so good drainage is vital for the plant to thrive.
Overwintering Rosemary Plants
- Prune the plant lightly to give it an overall shape-up near the end of fall. Tender shoots will likely die back. Follow the pruning with a light application of bonemeal sprinkled around the plant base and thorough watering.
- Apply a 2-inch layer of organic mulch, such as wood chips, around the plant to help the soil remain at a consistent temperature and prevent the plant from being uprooted by soil heaving. Soil heaving occurs when the soil goes through freezing and thawing cycles during the winter. As the soil expands and contracts, plant roots (and bulbs) often are heaved up and out of the ground. A layer of mulch acts as a blanket for the soil and prevents this from occurring.
- For extra protection, you can wrap your rosemary plant in garden fleece. Garden fleece, or horticultural fleece, is a fabric used to cover plants and give added insulation and protection from the wind. You may have seen some shrubs wrapped in burlap during winter. Garden fleece is a lighter material that will allow some light and more air exchange. If you live in Zone 4 or 5, or if you’ve had problems with rosemary dying over the winter, this is another tool to give your rosemary a better chance of survival.
Rosemary is an evergreen shrub, so if it’s not too cold, new growth could still appear throughout the winter. It will be minimal but should be observed for signs of dehydration. If the new leaf growth begins to look droopy it should be watered. Be careful to water at the soil level only so the leaves will not get wet and potentially freeze if the temperature dips below freezing soon after watering the herb.
If rosemary is being grown outdoors in a container and you want to keep it outdoors in the winter, move the container to a sheltered location next to a south-facing wall before the winter temperature dips below freezing. Go through the same steps of pruning, feeding, watering, and mulching just like an in-ground growing plant before moving the container. Any time during the winter when the temperature is above freezing and the sun is shining, move the container of rosemary in full sun for a few hours. This will help keep the plant healthy and thriving. Don’t forget to bring it back to the sheltered location before nightfall so frost won’t fall on it.
As a general rule, rosemary can survive some frost on the leaves, but frozen roots can kill the whole plant.
How to Overwinter Rosemary Indoors
For gardeners who live in zone 6 and colder, you’re better off bringing potted rosemary plants indoors. Fortunately, a container of rosemary is very easy to overwinter indoors – simply move the plant to a room that is not too cold and has a south-facing window. If you don’t have an indoor location with southern sun exposure, a grow light can be used. Rosemary, like other Mediterranean herbs, loves full sun, but can survive with even a fluorescent grow light or cheaper LED grow light.
Lightly prune, feed, and water the plant before moving the plant, especially if you’re transplanting from the ground into a pot before bringing it indoors. A teaspoon of bonemeal and a cup of compost sprinkled on top of the soil doubles as a winter feeding and mulch. You can also apply a light feeding of liquid fertilizer once or twice during the winter.
Rosemary overwintered indoors needs less water and much less fertilizer, but you will still need to water it if the top inch or so of soil feels dry. Rosemary tolerates dry conditions, but don’t allow the soil to completely dry out or your rosemary plant will die. Just as with rosemary overwintered outdoors, you can expect to see new growth, especially with adequate light. You can pick and harvest a few sprigs of rosemary throughout the winter as you would during the summer.
When spring arrives, move the rosemary plant to a warmer indoor location or outdoors for a few hours during the day. Gradual exposure to full sun over the course of a few days to a couple weeks will reduce the chance of your rosemary leaves bleaching in the sun. Prune, water, and feed it and the herb may reward you with some small purple blossoms. Expect new spurts of growth once your rosemary is re-established outside. Fertilizers with higher nitrogen, like bloodmeal, alfalfa meal, or a liquid fertilizer with a higher first NPK number will promote more leaf and branch growth in the spring.
Pro-Tip: What to Do with Extra Rosemary Cuttings
So, you’ve pruned your rosemary plant before overwintering, and now have extra sprigs of rosemary. If you don’t intend to cook them, don’t throw them away!
- Dry them. This is the most common thing to do with extra rosemary. Hang them up to dry and . Avoid a food dehydrator unless you have a very low temperature setting, as heat will make your rosemary lose a lot more flavor. After they’re dried, store them in an airtight container or grind up the leaves to make your own herb mix.
- Freeze them. If you love fresh rosemary, you can freeze rosemary sprigs in a resealable bag or airtight container and use them as you would fresh rosemary, with minimal loss of aroma.
- Remove the lower leaves and root your rosemary sprigs in water or soil, multiplying your rosemary. Rosemary is a bit finicky to root, but you will know if the cuttings have rooted after 4 to 6 weeks. Make sure your cuttings don’t dry out, and only the bottom inch or so of the cuttings are submerged in water. Changing your water every few days can reduce the chance of rot.