The days are growing shorter, and frost approaches. If you’re new to growing blueberries, you may wonder how to prepare them for the winter chill. Here, I’ll provide essential tips to help your blueberries return vigorous and healthy year after year.
I didn’t have much experience growing blueberries until I accepted an organic farming apprenticeship in 2017 in North Carolina. The farm featured about 150 mature and stunningly productive blueberry bushes of several different varieties. When the other apprentices and I arrived in March, the ground was still frozen. Our first major task was pruning and cleaning up the blueberry acre.
I remember those days of picking bucket after bucket of sun-warmed blueberries with such joy, recalling my purple-stained fingers. I can still remember the smell of sweet blueberry air when we made homemade blueberry jam. We added blueberry bushes to our farm in New Hampshire almost immediately after arriving, and we have future plans to add many more.
Preparing our blueberry bushes for winter is just one of the ways we show our love for them. Prep your blueberry for winter following these 7 easy steps.
Step 1: Remove Fallen Fruit
Clearing fallen blueberries under your bushes is crucial to prevent overwintering pests.
No doubt there are blueberries on the ground near your blueberry bushes. Whether they fell off over-ripened, blown off by the wind, or simply missed during harvest, cleaning up the area beneath the bushes in the fall is important. Various fungi, bacteria, and pest larvae can overwinter here, so you want to clear all the debris.
Sweet, fallen fruit will also attract critters passing through, which could lead to damage to other crops. The rotting blueberries may also attract yellow jackets that nobody wants in their garden or yard, so remove any fallen fruit to avoid these headaches or, if you’re unlucky, stings.
Step 2: Soil Test
Monitor and test soil fertility and pH annually to ensure optimal plant nutrient levels.
Monitor soil fertility and pH every year because amendments wash out of the soil, and nutrients decrease as your bushes access them. Soil test in the fall during garden cleanup, but don’t apply fertilizer until the following spring before leaves have formed. When the ground begins to thaw and perennials wake up, take this as your signal to feed anything that calls for it.
Best Fertilizers for Blueberry Bushes
For rhododendrons and azaleas, use Holly-Tone fertilizer at a rate of 1 cup per foot of branch spread.
If you grow rhododendrons, azaleas, or anything in the hydrangea family, you may be familiar with Holly-Tone fertilizer by Espoma. It’s one of the best foods for blueberries and a favorite among professional gardeners. While you don’t have to fertilize in the early winter, applying this in the late winter or early spring sets the stage for good growth!
Feed one cup of Holly-Tone for every foot of branch spread, and double that amount if your established bush has branches 3 feet or wider. At this time, you can also adjust the pH level, which we’ll discuss next.
Step 3: Check the pH
Blueberry bushes require an ongoing soil pH of 4.0 to 5.3 for optimal growth.
If you planted your blueberry bushes, you may remember they like the soil pH between 4.0 and 5.3. Any adjustments you made for this initial planting are not a one-time application.
Soil acidifiers contain elemental sulfur and gypsum and are used to grow many acid-loving shrubs and berry bushes.
To decrease pH levels:
You can decrease pH with sulfur, which comes in granular, pelletized, or liquid form. While liquid options are easier to apply, they may also wash away easier if you receive a lot of rainfall after applying them. Work granular and pelletized versions into the soil during your springtime fertilizer session. Apply soil acidifiers every 60 days until you have achieved the desired pH adjustment. At-home pH test strip kits provide instant results and are good to have on hand.
If pH levels remain too high, you run the risk of iron chlorosis. Symptoms include overall poor growth, yellowing leaves, and early defoliation. If you notice yellowing leaves in the spring, check pH levels right away because this is a sign of too high alkaline levels, usually over 6.0. You can apply chelated iron to the soil to provide an immediately plant-accessible source of iron, but most soils already contain ample iron, so this is only a temporary measure; preventing soil alkalinity is the long-term solution to ensure iron accessibility.
To increase pH levels:
Apply limestone according to the application instructions of the product you choose. The finer the limestone, the quicker it incorporates and increases the pH, and the more the pH needs to increase, the longer it may take. However, most soils are not acidic enough to cause problems for blueberries; it’s far more common to see extremely alkaline or neutral soil profiles in residential soils.
Should pH levels remain too low (below 4 pH), manganese toxicity could occur. Symptoms include crinkling and discoloration of leaves and chlorosis of young leaves. However, this is extremely uncommon in blueberries.
Pro tip: Avoid using aluminum sulfate, which can build up in your soil over time.
Step 4: Water Through First Frost
Properly water blueberry bushes using drip irrigation to maintain soil moisture.
Although blueberries don’t react well to being over-watered, it’s important to water your bushes consistently and thoroughly up until the ground freezes. The best option is using drip irrigation or soaker hoses to allow moisture to trickle down to the deep roots.
Watering well before a frost ensures your bushes are hydrated before the ground freezes, at which point, water will be inaccessible. A water gauge and soil moisture meter are simple tools that can help determine if you’re watering enough. Bushes should receive at least an inch per week all season and up to four inches when fruiting. The top inch of soil should be moist at all times.
Step 5: Protect from Snow and Ice
Protect blueberry bushes in cold winters with DIY low tunnels.
In areas with particularly cold and long winters, extra protection may be necessary. If your bushes are young and small enough to fit under a DIY low tunnel, make one by bending PVC pipes and covering them with greenhouse plastic. Don’t forget to weigh it down properly. To protect from harsh winds and heavy snow, stake the centers of your blueberry bushes to avoid breakage.
Consider growing later-season blueberry varieties like Elliott, Bluegold, and Coville to decrease the risk of early spring damage.
Frost Protection In the Spring
Protect your bushes from late spring frost to prevent damage to the flowers or buds.
As weather patterns change and spring temperatures fluctuate unpredictably, you should be prepared to protect your bushes in the unfortunate event of a hard late spring frost. An early spring frost can be extremely damaging to flowering peach and apple trees, strawberry plants, blueberry bushes, and many other crops.
Once bushes have begun to come out of dormancy, bud formation is encouraged. Spring and early-summer fruiting varieties will be the first to flower, so they are at a higher risk of frost loss in colder growing zones. Damage occurs when early spring temperatures spike, buds emerge, and then a late frost hits. If an extended hard frost hits while plants are flowering, there will be a significant loss across orchards and backyards.
If a late spring frost is imminent, you can help prevent late spring damage and loss by:
- Water overhead on a night you may experience a frost. This constant movement will help keep any buds present from freezing.
- Running fans as this can also assist in keeping frost from sticking to your buds.
- Use row cover to provide your bushes with a few additional degrees of warmth.
The length of the frost, the time of year, wind, and other external factors such as the dew point will determine how bad or if any damage occurs. Unopened buds have been known to withstand temperatures of 25°, but opened flowers and immature fruits will suffer damage and possible loss at 29-30°.
Cutting open the buds and inspecting the internal tissues is how you can determine the damage. If tissues are brown, dark brown, or black, there is likely damage or loss. Other times, damage may show itself in misshapen fruit or fungal diseases.
Step 6: Protect Against Critters
Use methods like fencing to deter animals from your garden.
Raccoons, deer, and mice love blueberries. Here are some options to keep them away over the winter and in seasons to come.
Scent Repellents
- Human or pet hair: Toss some hair or fur in and around your blueberry bushes. The scent of dogs and humans should deter most animals. Refresh the supply after a rainfall or once a week to keep the scent fresh.
- DIY essential oil solution: Mix about two tbsp of strongly scented essential oils such as peppermint, geranium, or lavender with 250 ml of water. Adjust the amounts if you need to make a larger batch. Shake it up thoroughly and spray around your blueberry bushes as needed. This will only last for a couple of days, so it will need to be regularly reapplied.
- Coyote urine: This gives animals the false sense that predators are nearby. Sprinkle out granular versions of it or store it in containers with holes poked through the lid. Rainfall dilutes this, so replace it as needed. Pro tip: Wear gloves or a face shield if you’re sensitive to strong odors. Coyote urine is strongly scented!
- Dog urine: Just like coyotes, dog urine warns some animals away. Helpfully, your pet dogs will handle this application on their own!
Sound and Visual Repellents
- AM/FM Radio: The constant sound of voices will also give animals the sense that humans are nearby, and typically, this will cause them to keep walking. Store it in a plastic bag if it’s during the rainy season, and change up the station every now and then. For a modernized version of this, you could place a waterproof Bluetooth speaker in the garden and control the music from inside.
- Pie tins on a string: Grab a few pie tins at the dollar store, poke a hole in them, and put them on strings. Then, tie them at sporadic heights on a t-post or sturdy garden stake. They’ll bounce around in the wind and scare off any skunks, deer, or mice who might have naughty blueberry bush ideas.
- Scare tape: This specialized tape shines and shimmers as it blows around in the wind. It’s effective during the day against birds and at night against skunks, deer, and groundhogs. Follow instructions on how and where to hang it properly so wildlife remains safe.
- Wrap with a burlap sack: This not only protects your bush against critters, but it adds an extra layer of warmth to boot!
- Motion-activated lights or sprinklers: Animals that wander through at night can often be deterred by a light suddenly turning on or a blast of water shooting at them. This is more effective against larger animals like raccoons or deer than against smaller ones like mice or squirrels.
- Fencing: If you’re able to install a fence to protect your plants, this is the most surefire way to ensure they are safe from damage.
Step 7: Mulch
Mulching with organic materials like pine needles and woodchips helps soil pH and moisture.
Mulching will help maintain the pH of the soil and retain moisture. Any organic mulch can be left in the garden and will naturally break down, like raked-up pine needles, straw, woodchips, or bark mulch.
Four to eight inches of mulch can be applied around your bushes. Pack it snugly but not so tight that the roots can’t breathe. Remember to pull back the mulch in the spring before fertilizing and adjusting pH. It can be put back over the base of the bush afterward if temperatures stay low.
Key Takeaways
- Clean up spent berries.
- Test every year and adjust pH as needed.
- Protect from the cold and mulch bushes.
- Keep critters at bay.
- Fertilize and prune in late winter or early spring when bushes have broken their dormancy.
Final Thoughts
There you have it: seven easy steps to prepare your blueberry bushes for winter. Just remember that blueberries need a specific pH level to thrive. They love organic matter and need extra protection if you live in an area where winters are particularly harsh. And don’t forget to prune them in late winter or early spring!
