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After tending to your herb garden all spring and summer, it’s sad to think that a rough winter might damage your plants. Luckily, there are several ways you can help your herbs survive the colder months, so that they thrive when spring rolls around again. While annual garden herbs such as dill, cilantro, and basil will die out at the end of the growing season, perennial herbs like rosemary, chives, mint, lavender, and lemon balm may go into dormancy in the winter, but will reemerge when the weather warms up again. With the proper care and attention, you can ensure your perennial plants come back and thrive next year.
Depending on how cold it gets in your region, some plants may need more or less protection and preparation to make it through winter. For example, rosemary is a more delicate perennial that benefits from extra protection from colder temperatures. Other herbs, such as mint, are hardier against winter weather and might only need a little coverage to help them thrive in the spring. Because of this, it’s important to know your herbs and how they’ll handle the winter months in your specific location. Whether you’re growing your herbs in containers or directly in the soil, preparing your garden for winter will allow you to continue harvesting delicious herbs from the same plants next year.
Cover herbs with mulch to provide protection and insulation
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Mulching is one of the simplest ways to shield your herbs from the cold and prepare them for winter. The layer of mulch helps to insulate the ground, keeping the soil temperature more consistent, so that the ground isn’t freezing and thawing repeatedly. This will also help to prevent the roots of your plants from heaving out of the soil. Chopped leaves, straw, pine needles, or bark are all great insulators for the roots of your plants and will keep them from getting too cold.
Depending on how much protection your herbs need and how low the temperatures drop in your area, you may only need 2 to 3 inches of mulch over the base of your plants. For locations that have more severe freezes or with more tender perennials, lay 3 to 6 inches of mulch around your plants following the first hard freeze of the season. Using a darker colored mulch like brown wood chips can also help to hold in a little warmth from the sun to further protect the roots of your plant. The mulch should remain covering your herbs’ roots until your plants start growing again in the spring, and you’ll want to ensure there’s no more threat of frost.
Relocate potted herbs indoors or to your garage to keep them from getting too cold
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If you’re worried about your tender perennials suffering through the cold in your garden, an easy solution is to simply move your plants inside or to a more sheltered area, like your garage or an enclosed porch, for the winter. This is a great way to prepare rosemary plants for winter so they come back thriving next season and would also be beneficial for other potted herbs, especially ones that are more prone to damage from cold weather (such as parsley and cilantro). Depending on how cold it gets in your area, your plants may do better inside your home, rather than in an unheated space like a garage.
To get your plants ready to bring inside, place them in a spot outside that’s more protected and leave them there until temperatures start dropping to around 40 degrees Fahrenheit. Once it starts getting colder, bring your herbs inside the house and set them in a cooler area that doesn’t get drafts from your heat vents. With warmer winters, plants can stay in your garage until spring. Your herbs will need to be near windows that provide a lot of natural sunlight in order to survive, and if that’s not possible, you may need to use artificial grow lights. While it’s best for your plants to get four to six hours of sun every day, this can be substituted for 12 to 16 hours of artificial light.
Stop fertilizing your herbs early to prepare them for winter
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Giving your herbs extra nutrients with a little fertilizer might seem like a good idea to prepare them for winter, but it turns out late summer or fall is when you should stop fertilizing your garden. Fertilizing your herbs at the end of summer or beginning of fall will cause the plants to start producing new growth, though these young stems and leaves likely won’t be strong enough to make it through the winter. Having to allocate their limited winter resources to new growth makes your herbs more susceptible to damage from the cold and could kill your plants.
To start preparing your garden herbs for winter, stop your fertilization routine sometime in August to help signal to the plants that winter is coming. In some cases, you may be able to fertilize until temperatures start to drop in the fall. Though you won’t want to promote new growth in your herbs before winter, you may want to consider testing your soil, so that you know what you’ll need to fertilize with in the spring.
Insulating your herbs with frost blankets or other coverings helps keep the cold out
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If mulching alone doesn’t seem to provide enough insulation to overwinter your herbs, or if strong winds are hurting them, another tip for protecting your plants from frost is to utilize a thermal blanket or other coverings. Frost blankets or thermal blankets come in different weights, allowing you to choose the right amount of protection for your winter conditions. When your winter weather holds temperatures that are consistently below freezing, frost blankets are an easy way to protect your herbs, whether they’re potted or in the ground, and they’ll also help your plants retain moisture. Other insulating materials, such as plastic sheeting or bubble wrap, can aid in preventing frost damage as well.
When covering your plants, you’ll want to ensure that air is able to flow in and out of the blanket, otherwise the herbs beneath could end up getting too warm on sunnier days. If thinner frost blankets aren’t doing the trick, heavier ones could be helpful, though they sometimes need structural support. Potted plants can be placed side by side and covered with the thermal blanket.
Some herbs will grow stronger in the spring if they’re cut back once the weather gets cold
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Though pruning too late in the fall can cause unwanted new growth, some herbs actually benefit from being cut back as winter arrives. In fact, cutting back certain herbs like thyme, oregano, lemon balm, and chives, will help them to become even stronger next season and thrive in the spring. Removing all those stems and leaves helps your plant to focus its limited water and light on keeping the roots and crown of your herb strong.
Since pruning your plants too early in winter could cause new growth that takes attention away from the roots of your herbs, it’s crucial to wait until after the first hard frost to cut back your herbs. Once that initial frost has passed, trim your herbs back so that they’re a few inches above the ground, or the soil line in your pot. For plants with woody stems, you may want to be a bit more conservative with how much you prune. Cover the remainder of your herbs with some soil before adding layers of mulch to keep your plants safe throughout winter.
Be careful not to overwater your plants as the seasons change
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As your herbs enter dormancy and prepare themselves for cold winter weather, they’ll drink less water than during their growing season. Because of this, you won’t need to water your garden herbs as frequently once the seasons change. An overabundance of moisture in frigid weather can lead to diseases such as root rot that’ll harm your plants, so it’s important not to overwater if you want your herbs to succeed next year.
Generally, it’s best to wait until the soil has dried out to water your overwintering herbs. If your herbs are kept outside and you’re having dry weather, watering them a little before a deep freeze can be beneficial. Depending on how you’re protecting your plants, they may need even less water. Herbs that are kept under frost blanket may not need to be watered at all, as they’ll retain more moisture, while other plants may need to be watered once every couple of weeks. Keep an eye on how dry the soil is to know if your plants need a drink or not.
Treat your garden herbs for insects before moving them inside
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Checking and treating your potted herbs for issues with insects is an important step you’ll want to take before bringing your plants inside for the winter. Certain herbs like sage, lemon balm, rosemary, bay laurel, and marjoram are prone to problems with spider mites and other pests when kept indoors over the winter. Inspecting your herbs for signs of pests and treating them before bringing the plants indoors can help your plants thrive and keep bugs out of your house, preventing your houseplants from becoming infested as well.
If you find that your herbs are suffering from a pest infestation, insecticidal soap and water are super helpful for killing the insects. Try rinsing the leaves and lightly washing them with the soap to remove the bugs and their eggs, or you can spray to combat the problem. Since indoor herbs can still struggle with aphids and spider mites, it’s a good idea to continue checking your plants throughout winter.
Avoid pruning near the end of summer and fall for better winter hardiness
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While there may seem to be no harm in harvesting herbs from your plants throughout the end of summer and fall, continuing to prune during this time leaves your plant less prepared for winter. Trimming your plants often promotes new growth, but in late summer and fall these new leaves and stems may not have enough time to become strong. This leaves your plant more susceptible to damage from the cold temperatures. Additionally, pruning in the autumn season doesn’t give the stems enough time to heal the cuts and decreases the herbs’ winter hardiness.
To ensure your herbs are as winter hardy as possible and will flourish next spring, you’ll want to stop pruning in late August. Making sure that you don’t harvest anything from your plants starting about one month before the first frost will also help to keep them strong throughout the bitter season. Taking these steps allows the stems on your herbs to mature fully before winter weather sets in and ensures they’re ready for the cold months ahead. Otherwise, wait until after the first frost to cut back your plants.
Use a shelter to insulate and protect your herb garden outdoors
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For those that live in colder areas and need more protection for their outdoor herbs, you can support heavier thermal blankets by utilizing a frame and creating a shelter to overwinter your plants. This helps to keep a steadier, warmer temperature for your herbs and stops frost from harming them. While you can buy a cold frame, floating row covers, or grow tunnels for an easier option, you might build a structure instead for a clever DIY idea that’ll protect your plants from frost. You’ll need to make sure that whatever kind of shelter you use has airflow to keep heat from getting trapped inside on warmer winter days.
Once your herbs have gone dormant, place your shelter over them. This should be done before the ground is totally frozen, and potted herbs should be grouped close together under the structure. The frame for your shelter can be built from PVC pipes, wood, or rebar to ensure it’s sturdy and will be able to hold your covering over your garden herbs. If you don’t have frost blankets, plastic sheeting and bubblewrap are great for insulating your plants and blocking wind. As spring starts to arrive, partially open your shelter to begin slowly acclimating your herbs before fully taking down the shelter. Depending on what kind of shelter you build or buy, it may be expensive initially, but will likely last for several years.
Transplant herbs in your garden into pots several weeks before winter starts
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If you have herbs in your garden bed that you’d prefer to keep inside or in a more protected place during the bitter months, many perennial herbs can be transplanted into containers and relocated. Whether you’re planning to bring your plants into your home or group them together inside a shelter, it’s important to dig up your herbs and replant them into your pots a few weeks before you’ll actually need to move them. By moving your plants into containers and allowing them to sit outside for a while, you’ll give them time to get established in the pot and prepared for winter.
Approximately two to three weeks before the temperatures are predicted to start dropping, begin uprooting your herbs from your garden and planting them in pots. If the weather has already started to get a little colder, try moving your herbs to a spot with better protection, like beside a wall that’ll block wind. Certain herbs like rosemary will need to be brought indoors ahead of the first frost, but others, such as mint, chives, and tarragon, don’t mind a slight frost before coming inside. When the weather starts to warm up again, set your potted herbs outside on warmer days to get some indirect sunlight and bring them back inside during chilly nighttime temperatures.
Get rid of weeds before winter fully sets in
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Unfortunately, some pesky weeds in your herb garden could come back in the spring, even if they seem to die out during the winter. If the weeds are perennials and had time to establish before winter, they may even come back with a vengeance, fighting with your herbs for resources when spring returns. Whether you’re planning to keep your herbs in your garden throughout winter or move their pots inside, you’ll want to get rid of any weeds to prepare your plants for the colder months and ensure they’re not competing for water and nutrients come spring.
With herbs like sage, rosemary, bay, and thyme that have woody stems, you’ll want to check around the bases of your plants and pull any weeds you spot before mulching. Potted plants should be weeded by October to make sure they’re ready to be insulated or come inside when the temperatures drop. After pulling any troublesome weeds, be sure to mulch your plants. This can help to stop weeds from reemerging and their seeds from growing as well next season, because it’s harder for the seeds to get sunlight. By removing weeds from around your plants, you can prepare your garden for winter and help your herbs to thrive again in the spring.
Heel in potted woody herbs for extra protection
For those who want to keep their containerized herbs outdoors during winter, but are worried about the roots getting too cold, burying the pots in your garden is extremely beneficial and a great way to insulate. While digging plants up every fall and replanting them in the garden each spring is a fine method, keeping your herbs potted all year, and then burying the pots in winter, will avoid any damage to the roots from being transplanted. Burying or heeling in your potted herbs will block the cold air from their roots, and in the spring you can easily remove the container from the ground.
It’s best to heel in your potted herbs in a somewhat protected area that isn’t overly wet. This could be a raised garden bed or a spot that has some coverage from wind. Simply dig a hole in the ground that’s slightly larger than your pot, making it easy to set inside, and place your herb so that the top of its container is level with the dirt. Pack in the soil so that your containers are firmly in place. You’ll want the pots to be buried close together for further insulation. By heeling in your herbs for the winter, you can keep their roots protected from freezing weather and ensure they’re healthy for next year.
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