How to Overwinter Strawberries in 6 Easy Steps
Are you trying to overwinter strawberries in your garden, but aren't quite sure where to start? In this article, organic gardening expert Logan Hailey walks through the entire process to overwinter strawberries to keep them alive and productive into next growing season.
Strawberries are one of the most popular and easy-to-grow garden fruits. They are widely adaptable in USDA zones 3 through 10 and are even native to North America. Strawberries are natural perennial fruits that actually enjoy (or even require) a certain amount of chilling to optimize fruit production.
However, temperatures below 15°F can fatally damage strawberry crowns if they aren’t protected. That’s why it’s important to ensure you take the proper steps to keep your strawberries productive into next growing season.
If you want to grow perennial strawberries in zones 7 or colder, use these simple steps to prepare your plants for a cozy winter so they can come back with prolific fruit in the spring. Let’s dig into everything you need to know about winterizing your strawberry patch.
Do Strawberries Need Protection From Frost?
Though strawberries are naturally adapted to freezing temperatures, the crowns can freeze and die in temperatures below 15°F if they don’t have winter protection. Their roots are fairly shallow and are sensitive to ultra-cold weather in northern zones. Strawberries usually only need frost protection in zones 7 and colder.
Fortunately, winterizing strawberries from frigid winter weather is as simple as pruning, mulching, and optionally using an insulating blanket or low tunnel. This process begins in the late fall just before the plants go dormant. The steps you take in the fall and winter will ultimately determine the amount of flowers and fruit your plants grow in the following year.
Note: Day neutral strawberries are bred to put a huge flush of energy into their first year of growth. Due to the affordability and wide availability of these varieties, it is often recommended to grow them as annuals.
Instead of winterizing day neutrals, many farmers simply mow them down or yank them up and re-plant the following spring for a more vigorous, disease-free crop. These overwintering practices work best for June-bearing and everbearing varieties.
Overwintering Strawberries in 6 Steps
If you don’t want to go through the whole process of replanting next year, you can easily winterize your plants to come back with a bang. Remember, the steps you take in the late fall are the major determinants of your berry yields in the spring.
In spite of their small size, strawberry plants are remarkably hardy. They can handle some major cold and are especially resilient when protected under a layer of mulch. However, the green shoots and flowers are very tender.
These winterization strategies only work for dormant plants with foliage that has died back to the ground. This “hibernation” period allows the plant to focus on root and bud growth while slowing its cellular processes until spring.
Step 1: Renovate Beds & Prune Plants
Strawberry bed renovation is a fancy term for pruning and cleaning up your strawberry patch. After the final berries have been picked and the weather starts to chill, it’s time to give your plants a little TLC. This usually overlaps with the late fall prunings of other perennials like lavender, bee balm, catmint, daylily, and some fruit trees.
To begin bed renovation, you need to remove any overgrown areas to ensure proper airflow and spacing. Most varieties do best with an 10-18” spacing, depending on your maintenance. Pull out any runners that may have rooted and started encroaching on the space of their mother plants.
Thoroughly weed the patch and make sure no weedy competitors are stealing resources from your crop. If you have any large weeds, take care not to pull up your plants with them.
Next, it’s time to prune back dead leaves and foliage. At this phase, most of the above-ground parts of the plant should look dead. The weather has triggered for the plant to drop its leaves (just like the trees) and prepare for a winter of hibernation. The leaves will turn red, brown, and start to fall. Pruning and removing these dead leaves is vital for preventing disease and encouraging new growth in the spring.
For small plantings, you can use hedge trimmers or hand pruners. For larger patches, use your lawn mower with the blade set at least 4” above the ground. This ensures that you don’t mow too low and damage the crowns or rip up the plants.
Cut back the plants about 1-2” above the soil line. You can hold the base with one hand to ensure you don’t pull them up. Check that the central crown is still intact. Each crown will look like a bundle of short, fleshy brown stems sticking up from the ground.
Any plant debris left in the bed can overwinter harmful strawberry diseases like botrytis, powdery mildew, and leaf spot. Removing plant debris is the number one best way to prevent diseases in your garden!
Step 2: Optionally, Fertilize in Late Fall
Adding a generous dose of fertilizer to fall strawberries will result in bountiful berries the next spring. Many people don’t realize that their plants actually form the fruit buds for next season’s crop during the previous autumn.
Fall fertilizer encourages more bud and root growth for stronger plants. On the other hand, spring fertilizer can cause an overgrowth of foliage and soft or mushy berries. It is especially important that you don’t provide nitrogen too close to the spring flowering period.
In the autumn, apply an all purpose fertilizer blend or a rich compost to your beds after you have pruned the plants. A balanced blend at a rate of 1.5 pounds per 100 feet is best.
I often just sprinkle a handful of Down to Earth 4-8-4 Rose and Flower blend around the base of each plant (not on the crown). In general, organic fertilizers are better for strawberries because they provide a slow release of nitrogen that ensures the plants won’t over-produce foliage in the following year.
Step 3: Apply Mulch
Once you’ve renovated and fertilized, mulching is the easiest (and most fun) part of the process. It is quite a joy to see children flinging straw around the garden to give plants a “cozy jacket” for the winter.
Pine needs or weed-free straw are the best mulch options for strawberries. You can also use dried deciduous leaves as long as there are no signs of pathogens.
Mulching your strawberry bed has so many benefits, including:
- Insulating the plants against temperature extremes.
- Preventing continuous freeze/thaw cycles by moderating soil temperature.
- Conserving soil moisture through the winter.
- Suppressing weeds.
- Preventing disease.
- Providing a dry surface for berries to rest in the spring.
- Improves the soil quality with more organic matter.
Spread mulch 2-4 inches thick over the entire surface of the strawberry beds. It is okay to cover the crowns because you can rake back the mulch in the spring.
While dormant plants can handle light frosts, you need to make sure you have applied your mulch before the temperature drops below 20°F.
Keep an eye on the weather and, when in doubt, apply sooner than later. I like to put the straw on as soon as the plants have gone dormant and I have finished pruning.
Step 4: Use a Row Cover if Needed
In the extreme cold of zones 5 and colder, you may need another layer of protection. Row cover is the most common winter protection used for commercial strawberries. This woven fabric allows some light transmission in (for early spring growth) while adding 2-8°F of warmth.
Some gardeners use low tunnel hoops for their row cover, but I recommend laying it directly over the plants and securing the edges with sandbags every few feet. This is especially important in areas prone to high winds or snowpack that may rip the fabric.
Thermal blankets or frost protection blankets are another popular option for maintaining strawberry plantings outdoors in the coldest regions. These fabric garden blankets prevent freezing air from directly hitting the plant while also capturing radiant heat from the soil.
They are often opaque (some people even use comforters), which means they need to be removed as soon as warm weather appears in the spring.
Plants cannot photosynthesize through these coverings. So, it’s vital that you only use them during your strawberry plant’s dormant phase (no green foliage left above ground). Again, lay it flat on the bed and secure the sides with sandbags, bricks, or something heavy.
Plastic Row Cover
Plastic is another option, but you need to be careful that you don’t confuse your strawberry plants. Clear plastic can be used to create a mini greenhouse over your plants. This can lead to earlier berries, but it can also cause them to break dormancy too early in the spring. That sets them up to die from an early frost.
This plastic is laid directly over the bed or over low hoops. It should not be confused with plastic mulch, which is usually black plastic that is laid over the ground and has holes punched in it for the strawberries to grow through.
In extreme northern climates, some growers use all three options: Black plastic mulch with plants growing through spaced holes, then a dense layer of straw over the crowns, and then plastic low tunnels to promote early spring growth.
Step 5: Move Potted Strawberries
If you grow strawberries in containers, you still want to prune, renovate, and fertilize them in the fall. You can apply a 4-6” dense layer of straw mulch over the top of the pot to add some extra protection.
However, the most important step for winterizing container strawberries is protecting the root zone. Unlike strawberries grown in the ground, container strawberries don’t have the insulating power of the soil. They are lifted above the surface (especially if in hanging pots) and need to be thoroughly warmed to prevent the roots and crowns from frost damage.
The most common way to do this is simple bubble wrap. You can tape it around the base of the pot and then move the plants to a covered area like an unheated garage. You can also use burlap, a blanket, or place the pot into a larger container filled with soil.
Because the plants don’t need any sunlight during their dormant phase, it’s also very easy to move them indoors until spring comes. Whatever you do, just be sure that the potting soil does not freeze, or your strawberries won’t come back.
Step 6: Keep Frost Protection Around
Once you’ve put your strawberries to sleep for the winter, it’s simply a waiting game. You need to be sure that the weather is reliably frost-free. The soil temperature is above 40°F before you uncover the plants.
Use a soil probe to check the temperature. Then remove any frost blankets or row covers gradually to allow the plants to adjust. If there is still a risk of cold weather, you don’t want your plants to start producing tender new leaves and flowers that could be killed by a sudden cold snap.
It’s best to wait until the expected last frost date to remove your strawberry frost protection. Then, you can lightly use your hands or a rake to brush aside the mulch from the center crowns of the plants.
When the weather is reliably warm and the plants are flowering, it is especially important to remove row cover or plastic so that bees can get in to pollinate your berries.
For containers, the same rules apply. Remove the mulch and bring the plants outdoors around the time of the last frost date. You can keep the bottom of the pot insulated until the weather has thoroughly settled.
Frequently Asked Questions
Should I cut strawberries back before winter?
Cutting back strawberry plants is highly recommended because it prevents disease and encourages a new flush of growth in the spring. Once the weather cools in the fall, the plants receive a signal to go dormant and drop their foliage. The dead or dying leaves need to be removed to keep the bed clean and disease-free. Cut back your plants to 1-2” above the ground and avoid damaging the center crown.
Can strawberries be left out over winter?
In zones 8 and warmer, strawberry plants can be reliably overwintered outdoors and will remain perennial. In zones 7 and colder, a deep mulch or other form of protection (row cover, frost blanket, or plastic) are helpful for encouraging more survivability. Temperatures below 15°F will kill strawberry crowns.
Should I put my garden strawberries in pots for winter?
Generally speaking, your plants are best left in the ground if that’s where they started. If you transplant them from garden beds into containers, you’ll run the risk of the plant enduring transplant shock, which can be even more detrimental during colder seasons.
Now that you know how to overwinter your garden grown strawberries, the next step is to take action to protect your plants. Strawberries are perennial fruits that will bring you plenty of fruit back each harvest if they are properly cared for. By following these steps, you’ll ensure you have plenty of fruit for the next several growing seasons!