Growing across the Northern Hemisphere, civilizations have been farming blackberries for food and medicine for thousands of years. They’ve been found in the stomach of the infamous bog woman known as Haraldskær Woman, whose remains were found in Denmark and date back 2,500 years. London distillers were known to have used blackberries in liqueurs during the Renaissance. And people all over the world today benefit from growing blackberries to enjoy in jams, pies and other delicious treats.
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Blackberries are a wonderful addition to any culinary garden. Able to grow in both containers and in the ground, once established these hardy perennials produce a sweet and tart fruit year after year. Growing blackberries is fairly easy once you know just a few key details about their life cycles.
Due to their short shelf life and delicately formed fruit, many blackberries found in grocery stores can be developing mold or are disappointing in the flavor department. This makes them all the more desirable in the culinary garden. But take care, as blackberry vines can become invasive.
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Quick Care Guide
All About Blackberries
The blackberry, Rubus fruticosus, is a shrub native to many regions of the Northern Hemisphere. Due to its delicious taste and generally easy to grow nature, they can now be found growing throughout the world, in the United States in zones 5-10.
Each blackberry plant is made up of several components. Shallow perennial rootstock forms the base from which long biennial stems called canes grow.
New canes (called primocanes) grow every year up to 6 meters in length but do not initially produce fruit. During their second year, canes (now called floricanes) produce lateral growth which then provides fruit. This fruit is actually a collection of 75-85 little individual fruits called drupelets clustered together to comprise the whole blackberry.
Types of Blackberries
There are four basic types of blackberries: trailing, erect, semi-erect, and primocane.
Trailing blackberries are preferred by many gardeners to work with, with thornless varieties often preferred. It’s recommended to use blackberry trellises to train the blackberry bush for easier access to fruit. These varieties are better for warmer southern climates.
A few popular varieties of trailing blackberries include Evergreen and Thornless Evergreen, a cold hardy variety that is popular for farming; Chester, another cold-hardy thornless variety with resistance to cane blight; and Columbia Star, a plant that produces lots of large, high-quality uniform fruit on thornless trailing canes.
Erect blackberry varieties are similar to their trailing cousins but do not need a trellis.These sturdy, thick canes are self-supporting.
Popular varieties of the erect blackberry include Arapaho, a midseason fruiter grown in zones 6-8 with good disease resistance; Kiowa, a variety with huge 3” fruit that produces early in the year; and Ouachita, a thornless cultivar that’s resistant to florette disease and produces heavily.
Semi-erect blackberries should still be grown with a trellis, but can partially support themselves. It’s only once these get fairly long that the extra support proves necessary.
Varieties that are popular include Triple Crown, a vigorous thornless grower in zones 5-9; and Hull, a thornless variety with medium to large fruit and good winter survival.
All of the above are biennial caning plants; they produce fruit on their canes during the second year of the canes’ lifecycle. The first year canes harden off.
But hybridization has produced the primocane blackberry. These are a hybridized plant that fruits on first-year canes, and in fact can sometimes produce two crops in a year in the right climate.
Popular types of primocane berries include Prime-Ark Traveler, a thornless early-season variety with heavy yields; Prime-Ark 45, the thorn-bearing companion to Traveler; and Black Gem, a thornless low-acidity primocane variety that can bear up to 15 pounds of fruit per plant per year.
Planting Blackberries
For first time growers wanting to learn how to grow blackberries, first assess your growing area. If planting in-ground, be aware that roots rapidly spread sideways enabling the plant to take over. If planting in containers, you can opt for a wide but shallow pot, as long as there’s at least 6-8” of soil depth. A 5-gallon shallow-but-wide pot will work well for most blackberries.
Grow your blackberry plant in well-drained soil. Blackberries thrive in full sun, but can tolerate partial sun as well. Heavily mulch 2-3 inches at the base of the plant to help conserve water.
When purchasing bare-root stock, find blackberry varieties specifically for your region. Blackberries can be grown in zones 5-10 but each type has its own requirements. In colder zones, be sure to plant after the last hard freeze. In zones with mild winters, gardeners have more leeway and can plant bare-root stock in late winter or early spring. Soak the roots in water for one hour before planting and place the roots one inch deeper than they were potted previously.
Care
Overall blackberries are fairly easy to care for. The most important factors are location, regular watering, and understanding blackberry pH and the biennial nature of the blackberry canes.
Sun and Temperature
Blackberries need at least 5-6 hours in full sun for a good harvest, but will still grow in shady conditions with a smaller harvest. Depending on the variety, blackberries can tolerate cold weather but generally need their canes protected from frost when temperatures drop below 28 degrees.
Water and Humidity
It’s best to grow blackberries in conditions that remain consistently moist.
For plants in the ground, try to water 1-2 inches a week at the base of the canes. Drip irrigation hoses are ideal for this. If in containers, you may need to water more frequently to keep the roots from drying out.
Try to avoid getting leaves or canes wet or watering late in the day as that can attract pests and disease. Spread 2-3 inches of mulch around the plant to help with water retention. While dormant, water about twice a month but not if temps drop below freezing.
Soil
Blackberries thrive in rich, sandy or loamy, well-draining soils. Adding lots of organic material to the soil will help with moisture retention, plus will break down and help feed your blackberry plants. They prefer a slightly acidic soil pH between 5.5 and 6.2. If you’re not sure of your soil pH, you can use a home test kit to get a good estimate.
Fertilizing
Fertilizing blackberries correctly helps to increase crop size. It’s important to fertilize twice a year, early in spring and again right after the berries have been harvested and old canes are cut back. If you’ve just planted bare roots, wait a month while the roots establish themselves before fertilizing. 2-3 inches of organic compost around the base of the plant should be enough to get your blackberry bushes started off right.
Try using an NPK fertilizer with equal parts (10-10-10) in early spring. This balanced ratio encourages even root and cane growth as well as leafing out. If you notice the bush isn’t fruiting, fertilize again using an NPK mixture that has less nitrogen in it such as a 1-2-1 ratio.
If blackberry plants appear to be struggling after two applications of fertilizer, instead of applying more, test the pH of the soil. Too alkaline soils often aren’t ideal for blackberry farming, and you may need to amend with agricultural lime or sulfur.
Pruning & Training
Blackberry planting requires two types of pruning at different times of the year.
Tip pruning is needed at the start of spring, when tips of new canes are cut back to 2-3 feet to encourage lateral fruiting growth.
Clean up pruning happens at the end of the harvest. Completely remove old year 2 canes that have fruited, but leave the new canes in place. Do this immediately after the harvest to prevent the spread of disease from the old canes to your new canes.
When pruning, use sterilized pruning shears to prevent disease spread.
For varieties that need trellising, let three to five canes grow per plant per year, trimming back excess and training the canes up a trellis or wire support. Using plastic plant ties, strips of fabric cut from old T-shirts, or other methods of securing your canes, you can provide extra support.
Propagation
Propagation is an easy and inexpensive way to plant blackberries in your garden. You can root a cutting by clipping a leafy stem about 4 to 6 inches in length and placing it one inch deep in rich soil. Keep the cutting damp but not wet in a shady location. Roots will form in a month or so.
If you find a blackberry shoot next to the blackberry parent, you can uproot it and relocate to a place of your choosing. This is the easiest method of propagation.
You can also propagate by way of tip propagation, where a portion of an existing cane is bent down to the ground and held in place by a metal stake. Over time roots develop from the tip of the cane touching the ground and create a new plant.
Harvesting and Storing
Blackberries provide a burst of flavor when homegrown. However, they don’t last long or transport well, so it’s important how you pick and store them.
Harvesting
Blackberries can take several weeks to ripen. Once ripe, place your fingertips gently around the point where the berry attaches to its stem and gently pull, trying not to squeeze the fruit. Ripe fruit will come easily off the plant. Unripe fruit may have some resistance and should be allowed to remain on the plant longer.
Storing
Store fresh, unwashed berries in an open container in the refrigerator. Place a paper towel overtop to absorb excess moisture. Wash them right before eating.
For long-term storage, you can freeze berries by spacing them out on a sheet pan in the freezer. Once frozen, move the berries to a sealed container or freezer bag. Making jams or jellies from your berries is another great way to store them, as long as you’re using a safe, tested recipe.
Troubleshooting
Blackberries are hardy plants but do succumb to pests and diseases that are common in their region. Let’s cover some of the most likely issues that might appear.
Growing Problems
When blackberries don’t grow to full size or form white drupelets, it is due to poor weather at the time of pollination and will most likely pass as the season continues. If drupelets are red, harvest berries when temperatures are cooler.
Pests
Leaf rollers, the larvae of tortrix moths, bore into canes and cause leaves to roll or yellow. During the growing season you can kill these pests by an application of neem oil, Bacillus thuringiensis (BT), spinosad or pyrethrin.
Spotted wing drosophila are an invasive bug similar to a fruit fly, and cause damage to the berries. Prevent these by setting sticky traps around your plants.
Blackberry aphids are a greenish-yellow aphid species. Use a hard spray of water to knock these off plants. Neem oil or insecticidal soap will kill their eggs. For large infestations, pyrethrin works well.
Raspberry beetles eat and lay eggs on the flowers or leaflets of blackberries. Their larvae tunnel into and destroy the fruit. Pyrethrin is effective against these pests.
The raspberry crown borer moth resembles a wasp. Their larvae dig into the crown and root system, and can cause entire canes to wilt. Beneficial nematodes may help kill off larvae, but infected plants should be removed.
Japanese beetles can skeletonize your plant’s leaves, and their larvae are off-white grubs that feed on roots in the soil. Spinosad works to keep these large, shiny green beetles away.
Strawberry weevils are small black or brown bugs whose larvae will kill the bud of an unopened flower. To combat, remove infected buds and spray with pyrethrin.
The strawberry root weevil is a different pest than normal strawberry weevils. These larvae feast on the roots of your plant, doing damage similar to raspberry crown borers. Apply beneficial nematodes to your soil to deal with these.
Finally, mites are possible annoyances around your blackberries. For these, neem oil can prevent their eggs from hatching on your plant, but for severe infections, use either spinosad or pyrethrin.
Diseases
Anthracnose causes sunken, reddish-brown lesions on young canes between leaves. As it progresses, these can become cankers and overwinter on the older canes. Leaves can drop early, and the fruit may dry up. Regular applications of neem oil can prevent this, but large outbreaks may require copper fungicide.
Botrytis in blackberries appears as a grey and hairy-looking mold on flowers and fruit. As with anthracnose, neem oil can act as a preventative, but copper-based fungicides are better for killing off the grey mold.
Powdery mildew causes a whitish powder to form on the leaves of plants, hence its name. These powdery fungi can reduce the plant’s ability to absorb sunlight properly. Neem oil is an effective treatment for powdery mildew.
Cane blight is caused by a fungi that creates large, brown cankers on the canes. Leaves may also wilt, a common first symptom that helps gardeners to discover the cankers. Horticultural oils act as a preventative measure, but copper fungicide kills the fungal source of the blight.
Orange rust is caused by a fungi, Arthuriomyces peckianus. It can overwinter in infected canes. Yellowish-orange spores coat the underside of leaves, and the cane growth can be stunted or spindly. Little to no fruit will form. There is no reliable treatment for orange rust, and plants that are infected with it should be removed and destroyed, not composted.
Frequently Asked Questions
Q: Do blackberries need a trellis?
A: Trailing or semi-erect varieties need to be trellised, either with a wood or wire trellis for support. It can be easier to install a wire trellis system at the time of planting to manage growth.
Q: Can blackberries be grown in pots?
A: Yes. Blackberries do very well in wide pots. While they do not need a lot of root depth, they do need space to move sideways to produce more canes. They may also need a trellis for support.
Q: Are blackberry bushes invasive?
A: Blackberries can be quite invasive. Be mindful of where you plant them and keep them contained so your garden is not impacted by runaway roots and canes.
Q: How many times a year do blackberries bloom?
A: Most varieties of blackberries bloom once in a season at the end of a two year growth process. However, primocane varieties may be able to continue to bloom and produce two or more harvests a year, depending on the type.
