Growing fruits reliably can be tricky for gardeners in colder climates. There is a balance required— some plants need a certain amount of cold exposure to fruit successfully, but too much frigid weather can damage some species.
Blueberry lovers in colder regions won’t need to worry when growing the ‘Duke’ variety. This northern highbush is one of the hardiest blueberries available, suitable for frosty regions around the United States.
They are also easy to grow when following these simple guidelines.
‘Duke’ Blueberry
‘Duke’ Blueberries:
- are cold-hardy
- thrive in USDA hardiness zones 4-7
- boast high yields
- ripen in early summer
- have a compact growth habit
buy at Epic Gardening Shop
Overview
Vaccinium ‘Duke’, prefers acidic soil, moderate maintenance.
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What Is It?
This variety is a prolific producer, yielding early and abundant blueberries.
‘Duke’ is a northern highbush blueberry variety known for its cold-hardy nature. These shrubs don’t mind a little chill, growing in USDA Zones 4-7. They produce flowers a little later in the season, avoiding issues with frost and ensuring cold-region gardeners don’t have to worry about frost protection.
Although flowering is later, this variety is also one of the earlier producers. You can typically start harvesting berries at the beginning of summer, unlike other varieties like ‘Pink Lemonade’, which only start ripening in the middle of the season.
The bush not only has berries that ripen early, but it also produces mountains of them – agricultural researchers assert it is one of the most prolific producers you can grow. You won’t have a shortage of delicious purple-blue berries to snack on if you choose ‘Duke.’
Planting
Ensure ideal planting conditions for maximum blueberry yields.
Once you’ve purchased your blueberry bush, you’re bound to be excited to get it in the ground. However, it’s best to give it a little time to adjust before you plant. Changing environments are stressful for any plant, especially when they’ve been growing in optimal conditions at the nursery.
For the first few days, keep your ‘Duke’ blueberry in a partially shaded area in its container. Avoid areas with high winds, as this can increase stress. Keep the soil lightly moist but not waterlogged until you’re ready to start the planting process. Don’t wait too long either – they only need a few days to adapt and limit shock. Plant within the first week in the shrub’s final home.
Once your blueberry bush is acclimated, choose an ideal location for planting. Full sun is best for the highest possible yield, but these plants can also grow in partial sun.
Soil is an important consideration, as blueberries are acid-loving plants. They won’t be happy in soil with a pH above 5.5 and prefer an even lower pH around 4.5 for the best possible growth. Test your soil and amend it until you achieve the right pH before planting.
With your location identified, start digging the hole. It should be around twice as wide as the container and only slightly deeper, encouraging the roots to grow outwards into the soil. Lower the bush into the hole and plant at the same level it was at in the container, filling in the gaps with rich soil mix.
Press down around the base of the plant to settle the roots in place and remove any large air pockets that may require a soil top-up. Water immediately after planting to prevent any further stress and encourage the roots to stretch deep into the soil.
If you’re planting another blueberry bush simultaneously, leave at least 5 feet of space between each plant. Overcrowding can increase your risk of disease in both plants and increase competition for resources. However, growing multiple blueberries will improve pollination and overall yields.
Planting in Containers
Opt for an acidic potting mix to meet blueberries’ pH needs.
If you’re short on space or you don’t have a backyard to plant in, you can also grow in containers. The bushes may not grow as large or produce as much, but you can still get to harvest fresh blueberries season after season without a massive garden.
The most important factor to consider is soil. It needs to be well-draining to prevent waterlogging but rich enough to retain moisture and feed the plants. It’s best to choose a potting mix for acid-loving plants to provide the pH that blueberries need to grow successfully.
The bushes can grow quite large, so choose a container that can accommodate their mature size. A 60 gallon grow bag should do the trick. You can keep the plants compact with regular pruning, but you’ll get to harvest far more berries if you let them grow to their full potential (or as close to full potential as you can get in a pot).
Planting your ‘Duke’ blueberry in a container means you will need to give them more attention throughout the season. Water more often, as the soil dries out quickly in containers, and feed regularly during the growing season to combat nutrients lost in the soil.
How to Grow
Blueberries aren’t too fussy, as long as they are planted in the right location. Follow these guidelines to ensure you get the biggest harvest out of your plants.
Light
Consider sun exposure when planting, and avoid shade from trees or buildings.
Blueberries are full sun plants. They grow best when given at least six hours of direct sunlight per day. In cooler regions, aim for around eight hours per day for the highest possible yield. These bushes can grow in partial sun, but this will negatively impact flowering and berry production.
When planted in the wrong position (with too little light), the branches will become leggy, and you’ll notice a lack of flowers. Unless you’re growing them for foliage only, I wouldn’t recommend giving them anything less than 4.5 hours of direct sun per day.
When choosing your planting location, take the position of the sun into account throughout the day and the seasons. You don’t want to plant in a spot that’s shaded by a nearby tree or your home at some point during the day. This could cause the plant to miss out on sunlight during crucial seasons like spring and summer.
Water
Inconsistent watering affects flowering and fruiting.
Immediately after planting, your blueberries will need frequent and consistent watering. This is usually around twice per week for the first season, depending on rainfall. In wetter regions, you won’t need to worry about watering as long as the soil remains lightly moist.
Once the roots grow deeper into the soil, they can handle less frequent watering. You can limit watering to around once per week when there is no rainfall. You may need to water slightly more often during warmer weather, so monitor the soil to ensure it doesn’t dry out completely and become compacted.
Watering inconsistently can lead to issues with flowering and fruit development. Too much water can lead to deadly problems like root rot. Too little will lead to stress that affects flowering and fruiting. Monitor both the bush and the soil regularly to look for signs that you need to adjust your watering plan.
Also remember to water you bushes more often in containers, particularly in summer. The soil can dry out daily in the summer sun, requiring additional watering every morning to support fruiting.
Soil
Amend your soil with peat moss or pine bark for optimal growth.
‘Duke’ blueberries are quite particular about their soil. It needs to be well-draining (as it does for most plants) to allow air to flow around the roots and prevent fungal growth. But they also have strong preferences for acidic soils, growing best in soils with a pH of around 4.5.
The range to aim for is between 4 and 5.5. If your soil has a pH higher than 5.5, you will need to amend it before planting. Incorrect pH levels will negatively impact growth, flowering, and fruiting, so this is not a step to skip if you want a strong harvest.
First, test your soil. You need to know the pH level to understand how best to amend it. If the pH is above 5.5, amend the soil with peat moss or pine bark to slowly adjust the pH levels to what your blueberries prefer.
Temperature & Humidity
Plants benefit from proper spacing and pruning for airflow.
As mentioned, one of the major benefits of growing the ‘Duke’ blueberry is its tolerance of cold. These plants grow best in USDA Zones 4-7 and require 800-1000 chill hours to produce an abundance of berries. You won’t have to worry much about frost damage or extra protection – these bushes are tough.
They don’t have any specific humidity requirements. However, it’s important to remember that higher humidity levels lead to more moisture around the plants, increasing the risk of fungal disease. Powdery mildew is possible and more common in areas with high humidity. Regular pruning and planting with the correct spacing can improve airflow around the branches to manage these issues.
Fertilizing
Opt for acid-loving plant fertilizer and mulch replenishment for soil health.
Blueberries are not typically considered heavy feeders. However, that doesn’t mean you should skip feeding altogether. Your ‘Duke’ bush will appreciate an annual feeding to replenish nutrients in the soil and avoid any possible nutrient imbalances that may impact fruiting.
While it’s important to feed, blueberries don’t require much additional fertilizer. One annual feeding in spring will provide everything they need to thrive in the upcoming season. Only apply the amount recommended on the packaging, never more, as this can stunt growth.
Look for a fertilizer specially formulated for acid-loving plants. To slowly replenish soil structure over time, replenish your mulch layer after planting.
Maintenance
Share berries cautiously with wildlife to preserve your own supply.
In the third year of growth, your blueberries may start looking a little leggy. To reinvigorate growth and improve production, prune from the third season onwards in winter when the plant is dormant. Never remove more than one-third of the plant at a time, and only trim what you need to (crossing branches or diseased sections) to boost health.
To protect your harvest from birds and small animals, install netting around the bush. You can share the berries with local wildlife if you have enough, but you will be risking the amount of fruits you get to eat yourself if you don’t protect them.
Harvesting
Frequent watering is needed for container bushes in summer.
The best part of growing the ‘Duke’ blueberry variety is harvesting time. Even though the flowers develop relatively late in spring, the berries are one of the first to ripen. You can usually pick the first few berries when they change color at the start of summer, continuing throughout the season.
Pick early in the morning before the summer heat lowers moisture levels in the branches. Also, pick gently, as the fruits bruise easily. Once picked, eat them fresh or place them in the refrigerator for storage rather than leaving them out. You can also freeze them if you want the berries to last a little longer.
Propagation
Transplanting cuttings promotes growth in larger pots.
To expand your ‘Duke’ blueberry collection, propagate from cuttings. Softwood cuttings are ideal as they generally root quicker, but you can also take hardwood cuttings in winter to propagate if you prefer.
Take softwood cuttings in late spring. Your cutting should be about 6 inches long, or slightly shorter depending on the growth on the branches so far. Dip the cut end in rooting hormone and plant into a mix of peat moss and perlite. Cover the container with a clear plastic bag to trap humidity and keep the soil lightly moist until new growth appears. Follow the same process for hardwood cuttings in the winter, ensuring you’re using the right rooting hormone to stimulate root growth.
Once the cuttings have started growing and are beginning to fill out their containers, transplant them to a larger pot with a potting mix for acid-loving plants.
Common Problems
Leggy growth may result from insufficient sunlight or improper pruning.
Blueberries are not difficult plants to grow, but they aren’t without potential problems either. Look out for these issues and adjust the environment accordingly:
- Lack of flowers: Limited sunlight or issues with soil pH.
- Lack of berries or poor-quality berries: The same causes as above, along with inconsistent watering, small animals and birds, or inadequate pollination.
- Leggy growth: Lack of sunlight or incorrect pruning.
- Pests and diseases: Not particularly common, but common garden problems like aphids, beetles, or fungal diseases like powdery mildew can negatively impact growth.
Final Thoughts
For gardeners in colder climates, there is no better choice than ‘Duke’ blueberries. Plant several if you’re looking to maximize your harvest.
