Part 2 of 4
by Halton Master Gardener, Liza Drozdov
What’s better than harvesting your own fresh berries for dessert or breakfast every day? It’s easy to do and won’t require much space in your garden. Blueberries are very hardy plants, and they grow easily and fruit prolifically in the wild, so you know they can produce well in the home garden, with little fuss. They’ll accept poor quality soil with low fertility, and some are hardy to zone 3. They all have lovely pinkish white flowers in the spring and they provide beautiful autumn colour, so even if they didn’t have delicious fruit they’d be worth growing. There are two main types of blueberries grown in gardens:
- Highbush (Vaccinium corymbosum)
- Lowbush (Vaccinium angustifolium).
They are quite different in their growth habit and management, but produce essentially the same delicious blueberry. There are many cultivars and crosses and named selections of blueberries, all with different growth habits and sizes. Regardless of what cultivar or named variety of blueberry you decide to grow, one thing is non-negotiable: Acidic Soil
A soil with a pH of 4.5 to 5.5 is essential for growing blueberries or other acid loving plants like rhododendrons or azaleas. Without it, these plants can’t absorb nutrients in the soil. Easy to use soil test kits are available in many stores to test your soil’s pH. Since most soils in Ontario are not acidic, you will likely need to amend your soil. Blueberries prefer lots of organic matter, ideally made from peat moss and leaf mould. Since very few areas in Ontario have suitable soil, one solution is to grow blueberries in special raised beds, filled with appropriate ericaceous soil. Elemental sulphur can be added the year before planting to bring the soil pH down, and an annual mulch of pine needles, peat moss and fallen leaves will help the plants thrive. They are sensitive to many fertilizers and fertilizing them at all might do more harm than good. If you feel you must feed them, use one for ericaceous plants, like rhododendrons.
Blueberries will die in alkaline soil, so containers–providing they are large enough–are another solution. Also, it’s better to water them with rainwater if possible, as tap water in some areas is also quite limy and unsuitable for blueberry cultivation. Blueberry plants are naturally resistant to diseases and usually don’t seem to suffer much insect damage in the garden. What causes them the most problem is the wrong soil or watering the plants with alkaline water. Blueberries are technically self-fertile, but to ensure good pollination you should plant several plants, as well as a few different varieties, together. That will help you get a larger crop, and if you plant early, mid and late-fruiting varieties you can extend your harvest season. This works because the plants flower at more or less the same time, even though the ripening season is staggered. As with all berry crops, birds are the competition. Your plants need to be netted to keep them from stealing your fruit. All will crop better in consistently moist, but not waterlogged soil. A good layer of mulch will help them retain moisture. A natural woodland plant, they will tolerate partial shade but will fruit much better in full sun.
Highbush Blueberries
Highbush blueberries seem to be the most readily available plants in the garden centers, and there are several cultivars commonly on sale. These shrubs can get up to ten feet or more in height, so it’s worth looking out for lower-growing and more compact cultivars for the home garden.
Highbush blueberries have shallow fibrous roots that are very close to the surface, so you need to be very careful when cultivating around the base of the plants. Spread a thick layer of mulch to help keep the roots fed and cool during the hot summer. They don’t need much pruning or managing in the way of raspberries or strawberries. They do not require an annual pruning; just let them grow and remove dead and damaged branches as you see them. Blueberries will only flower and produce fruit on two and three year old growth–so you need to let the plant grow to allow for fruit to form. But, once the branches get older and stop producing, prune out a third of the older growth every year to keep the bush producing.
Lowbush Blueberries
Lowbush blueberries are what we loosely call “wild blueberries” and they are the plants that are cultivated commercially. They are very low-growing plants, only around 12″ tall, and they naturally grow in rocky, sandy barrens, and peat bogs and are very tolerant of extreme cold. Unlike the Highbush blueberry with its shallow fibrous root system, the Lowbush blueberry has a taproot and a deep underground system of rhizomes and roots that help it tolerate drought and dry soil, acidic low-fertility soil, and even fire. For decades commercial Lowbush blueberry fields have been maintained by periodic burning. However, they are intolerant of urban pollution, so shouldn’t be planted next to streets or in inner city areas.
Lowbush blueberries spread by stolons or rhizomes under the soil, and are easily grown from a seed or a cutting taken from an existing plant. Not generally as available as Highbush blueberries in nurseries, but it is well worth the effort to find and grow them. While there aren’t many different Lowbush cultivars available, their genes have been bred into many Highbush blueberry cultivars. That adds soil tolerance, winter hardiness, sweetness of fruit and lower height. Lowbush blueberry fruits are smaller in size than Highbush, but have more intense flavour, and they may have a higher anti-oxidant content than Highbush varieties.These plants require specific maintenance to grow them successfully. Lowbush blueberries bear fruit only on second year wood so need to be grown on a two-year crop rotation cycle. The first year they are allowed to produce vegetative growth. In the second summer, plants will produce a crop from the flower bud developed the previous fall. Then after harvest they are burned or mowed to the ground to start again. If allowed to keep growing, the plant will become dense with vegetation which will shade the following year’s flower and reduce bud development and berry production, so growers cut them back to the ground every second year. To make sure you get an annual crop from your home garden, divide your planting in half, allowing one half to bear fruit every other year and alternating between the two.
Blackberries
Blackberries, or brambles, are closely related to raspberries, and their care is very similar. These plants provide lots of spring blossom and are very attractive to pollinators. Birds also enjoy the fruit, so they are an excellent choice for a wildlife garden. Brambles are native to woodland sites so they prefer a rich woodland soil –one that is full of organic matter. They dislike heavy, wet, waterlogged soil. Blackberries grow and fruit well in part shade so if you don’t have a lot of sun in your garden this is one of the best choices for berries. Blackberries will sucker and spread vigorously throughout the garden and quickly take it over if you aren’t vigilant. They need a good root run and are definitely too vigorous to thrive in a container. Blackberry canes will grow longer and taller than raspberries, and the clusters of fruit are larger and heavier, so they will need to be well supported and tied in carefully. They can bear fruit on canes that are up to two or three years old. However, the older the cane, the less productive it will be, so it makes sense to treat them as a raspberry and cut the canes down after their second year. Be sure to tie in the new canes as they grow in the spring, or they will quickly become a tangled mess.There are several cultivated varieties available. Blackberries are tough, reliable plants with few pest issues. Mulch the plants with manure or compost to reduce weeds and fertilize in spring with a balanced organic fertilizer like fish, blood and bone meal, topped with a thick layer of compost.
Did you know?
Vaccinium corymbosum, known as Highbush Blueberry, is native to eastern North America where it typically grows in moist woods, bogs, swamps and low areas. It makes an excellent addition to a native garden with its pretty flowers, summer foliage and brilliant fall colour. It also makes an excellent hedge with the added benefits of fruit which can be harvested or left for the birds
Halton Region Master Gardeners 