If you’re looking for me in August, there’s a good chance you’ll find me beside our highbush blueberry hedge, picking a big bowl of juicy berries. Once relegated to an out-of-the-way spot near the vegetable garden, fruiting perennial shrubs like highbush blueberries are now being recognized for their ornamental value, and being invited to take centre stage in gardens and landscapes.
Highbush blueberries are perhaps the best example of an “edimental,” a term coined by Norwegian author Stephen Barstow to describe plants that are both ornamental and edible. They offer four seasons of interest, which begins in spring, when the charming bell-shaped, white to pink blooms unfurl. These are followed in midsummer by the large, deep purple-blue fruit, giving us weeks of sweet-tart berries. With the arrival of autumn, the foliage morphs from green to fiery red, lighting up the landscape for about a month with a brightness that rivals that of burning bush (Euonymus alatus). Finally, as the leaves drop and winter closes in, the reddish colour of the new stems becomes visible, as does the peeling bark of the older branches.
Highbush blueberries are related to other North American native berries, including cranberries, huckleberries and, of course, wild (lowbush) blueberries. However, highbush and half-high varieties, which are a cross between highbush and lowbush blueberries, are bred to be bigger and more productive than their wild ancestors, forming multi-stemmed shrubs that grow from 18 inches to 7½ feet (45 cm to 2.4 m) tall, depending on the variety.
In the home garden, you’ll appreciate their good pest and disease resistance, when compared to other types of fruiting trees and shrubs, and their long harvest season, which can be extended even further by growing a mix of early, mid-season and late-producing varieties. And it’s not just gardeners who find highbush blueberries to be exceptional garden plants; they’re also attractive to native bees, and when the flowers are in full bloom, there’s no mistaking the distinct “buzz” coming from the garden.
Because highbush blueberry plants can live — and produce — for half a century, or even longer, it’s important to start with the right site. Don’t be afraid to think outside the vegetable garden; highbush blueberries make excellent hedging or screening plants, but also add interest to shrub and perennial gardens, entranceways and foundation plantings.
Look for a spot with plenty of sunshine, at least six hours per day, and decent, well-drained soil. Blueberries have shallow, fibrous roots systems and cannot tolerate wet feet or heavy, clay soil. If the soil is poor or not well drained, consider planting in raised beds. Blueberries also need slightly acidic soil, with a pH in the 4.5 to 5.2 range. If you don’t know your soil pH, it pays to get a soil test and make any necessary corrections before you plant. Applying elemental sulphur to the soil is the most common way to lower pH, but it’s a biological process and will take several months to take effect. If possible, acidify your soil the autumn before you intend to plant.
Early spring is the best time to plant; it gives the shrubs a chance to settle in and start putting out new root growth before the summer heat. Blueberries are shallow rooted, so there’s no need to dig deep. Instead, make the planting hole only slightly deeper than the container they were purchased in, but three times as wide. This gives the roots plenty of room to spread out. Add several inches (8 cm) of compost or leaf mould to the planting hole. Space plants five to six feet (1.5 to 1.8 m) apart, or four feet (1.2 m) apart if you’re planting a hedgerow. Space half-high varieties three to four feet (90 cm to 1.2 m) apart.
After planting, water well and protect the shallow root system with a four-inch (10-cm) layer of bark mulch or woodchips. Newly planted shrubs will need a weekly watering if there has been no reliable rain. Next comes the hard part: rub off (remove) any blossoms that appear that first year; this will send all the energy back to the plant and stimulate vegetative growth. In subsequent years, feed your plants a balanced organic fertilizer, such as 4-4-4, each spring.
Established highbush blueberry plants will yield, on average, about six pounds (3 kg) of berries each summer. To keep the birds from enjoying your homegrown harvest, drape a length of bird netting overtop the bushes, weighing down the bottom so the birds can’t sneak beneath.
Blueberries are bothered by few pests, but you should keep an eye out for issues like mummy berry and blueberry maggot. Mummy berry is a common fungal disease that causes fruit to shrivel. Pick off infested fruits when they appear. The fungus overwinters on dropped berries; reduce by removing the mulch and replacing with fresh materials. Blueberry maggot is the most common blueberry pest, but doesn’t harm the plant; instead it affects fruit quality. The adult form is a small fly that lays its eggs in the developing fruits. Once hatched, each berry will have a tiny white worm inside. Not so appetizing! To discourage blueberry maggot, plant dill or cilantro, or place pots of mint near your blueberry shrubs. These will entice parasitic wasps, a major predator of blueberry maggots. As well, certain varieties, like ‘Northland’, show resistance to blueberry maggot.
Good pruning will encourage healthy plants, high production and large berries. For the first three years, pruning will be minimal; remove only dead, damaged or diseased wood. Once the plants are well established, in about year four, the annual haircut can begin. In year four and five, the pruning will be relatively light, but once the plants are six years old, heavier pruning can begin. Expect to remove at least one-third of the wood at each annual pruning. The prime time to prune is late winter or very early spring, when the foliage is absent and it’s easy to get a sense of the structure of the plant and what should be removed.
A healthy shrub will have six to 12 canes that emerge from the base and support the fruit-bearing branches and shoots. Canes that are three to six years old are the most productive, so your first cuts should remove those that are older than six years. These will be thick at the base and often have lichens growing on the bark. Removing old canes will also open up the plant, allowing more light and air to penetrate the canopy, minimizing the risk of disease.
Once you’ve cleaned up the old canes, move up to the canopy of the plant with the aim of eliminating weak, twiggy growth. Blueberries are produced on one-year-old wood — the shoots that grow laterally off the branches. You can tell fruit buds from leaf buds by their size and shape: fruit buds are swollen and tear-shaped; leaf buds are small and pointed. Prune out dense, twiggy shoots that only have one or two fruiting buds, leaving lateral shoots that are at least four inches (10 cm) long with a good number of fruiting buds. This will result in larger, better-quality berries.
I’m not sure who is more impatient for that first harvest: me or the kids. Probably me! But I’ve learned that you can’t rush ripening. Wait until the berries have turned from green to reddish purple to deep blue, and then wait an extra two or three days for the sweetness to fully develop. For unusual varieties like ‘Pink Lemonade’, a taste test is the quickest indicator of ripeness.
The best blueberries for a season-long bounty
Certain varieties are described as “self-fruitful,” but all highbush blueberries will produce significantly more berries when two or more different varieties are grown. To ensure good pollination, plant them no farther than 100 feet (30 m) apart. Highbush blueberries are hardy in Zones 4 through 7, but ‘Northblue’ is very cold tolerant and can be grown in Zone 3 with winter protection.
‘Patriot’ is among the best of the early-season varieties and has been a garden favourite for 40 years! The compact shrubs grow up to four feet (1.2 m) tall and are cold hardy, reliable and tolerant of various soil conditions. As for the fruit, expect medium- to large-sized berries with a juicy sweetness.
In our Zone 6 garden, ‘Bluecrop’ is a superstar, bearing heavy clusters of medium-sized berries with the classic sweet-tart blueberry flavour. It’s considered a mid-season variety, cropping in July, and is one of the most widely grown highbush blueberries in the world. The four- to six-foot (1.2- to 1.8-m)-tall shrubs are disease resistant, cold tolerant and very productive.
This is an early- to mid-season variety that does well in regions with cold winters. The blooms are very attractive, opening pink but maturing to white. The medium-large berries that follow are deep blue and very sweet — dessert quality. The plants will grow up to six feet (1.8 m) tall, but have a slightly spreading form that needs annual pruning to keep it tidy and productive.
This is a called a half-high, which is a cross between highbush and lowbush blueberries. It’s ideal for small gardens or container growing, as it only reaches two to three feet (60 to 90 cm) tall. ‘Northblue’ is very cold tolerant, growing to Zone 3 with protection. The plants aren’t large, but the mid-season berries certainly are, growing quarter-sized, with a deep blue colour and sweet flavour.
‘Northland’ is a great choice for a small garden or a medium-sized hedge. It forms compact four-foot (1.2-m)-tall shrubs with sturdy branches that resist breaking, even under heavy snow load. The medium-sized berries ripen in midsummer and have a flavour similar to that of wild blueberries. It offers some resistance to blueberry maggot.
One of the oldest cultivars, ‘Jersey’ is still extremely popular. It’s also very cold hardy, tolerating temperatures down to -35°C. The plants will grow up to 7½ feet (2.4 m) tall and produce a mid- to late-season crop of small- to medium-sized blueberries.
Unlike most blueberries, the fruit produced on ‘Pink Lemonade’ is bright pink, and is packed with sweetness. The plants are also pretty, growing up to five feet (1.5 m) tall and having showy pink flowers in spring. Fruit ripens mid to late season.
Growing just 18 to 24 inches (45 to 60 cm) tall, this compact plant is surprisingly productive, yielding a good crop of mid-season large, sweet berries. ‘Peach Sorbet’ is a true edible ornamental, with attractive peachy-pink new foliage that matures to a rich green. Plant it as a low edging or in pots on a sunny deck.
Ideal for containers, ‘Jelly Bean’ is a mid-season dwarf blueberry that grows only 12 to 24 inches (30 to 60 cm) tall. The fruits are sweet with a flavour that’s often compared to homemade blueberry jelly, and they make a convenient snack on decks and patios.
5 simple steps to growing blueberries in containers
Cultivars of dwarf and half-high blueberries adapt well to container culture and can be grown on sunny decks and patios. The fruits add edible interest, but the foliage is also decorative. As with garden-grown blueberries, you’ll need to grow at least two different varieties to ensure good pollination.
- Start with two (or more) big pots (at least 18 in./45 cm in diameter) with drainage holes and fill with bark-based acidic soil.
- Pick compact, dwarf cultivars like ‘Jelly Bean’ or ‘Peach Sorbet’.
- Place the pots in full sun, watering often. A two-inch (5-cm) layer of bark mulch applied to the soil surface helps conserve moisture.
- From spring until midsummer, feed monthly with a half dose of an organic water-soluble, balanced fertilizer, such as 4-4-4. Late feeding can encourage soft growth late in the season, so stop fertilizing by August 1.
- Overwinter by sinking the pots into the ground and mulching with straw or shredded leaves.