*Editor's note: Growing Blackberries in Your Home Garden is being revised. This text is taken from a similar publication, Growing Berries on the Oregon Coast: Raspberries and Blackberries by Cassie Bouska, Emily Dixon and Bernadine Strik. The information here applies to Western Oregon.
If you are reading this publication for the first time, we recommend you first read Growing Berries on the Oregon Coast: An Overview (EM 9177). It includes general information on site selection, soils, irrigation, mulching, nutrient management, and considerations specific to the coastal environment.
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Oregon is known around the world for its blackberries. We have an ideal climate, with warm, clear, summer days and cool nights, so our berries reach peak flavor and quality.
Blackberries include types with a trailing, erect, and semierect growth habit. The raspberry-blackberry hybrids (e.g., ‘Boysen’ and ‘Logan’, also known as “boysenberry” and “loganberry”) are trailing blackberries.
Blackberries have an unusual growth habit. The plants have a perennial crown (plant base) and root system, and biennial aboveground canes. There are two types of fruiting habits:
Blackberries can be distinguished by their fruit. Both raspberries and blackberries produce an aggregate fruit of many drupelets (the individual sections of the berry, each of which encloses a seed). However, when raspberries are picked, the fruit comes off the receptacle (white central core that stays on the plant) and the berry is hollow inside. In blackberries, the receptacle stays attached to the fruit when picked. It is part of the fruit that we eat; thus, blackberries are not hollow.
There are three main blackberry types; they are differentiated by their cane growth habit — trailing, erect, and semierect.
Some blackberry plantings can produce for over a decade, so you should carefully select an ideal location for planting. Direct, full sun is best for good fruit production. Blackberry plants can tolerate partial shade, but yield and fruit quality may be lower. Blackberries prefer well-drained, fertile, loam soil with moderate water-holding capacity. Blackberry plants are tolerant of wet, heavy soils.
Wind can damage blackberries. Windbreaks (such as a row of trees or shrubs) can provide protection, but be careful where you establish them to avoid competition with the berry crop. See Windbreaks for Fruit and Vegetable Crops listed in “For more information.”
Blackberry plants require soils with a pH range of 5.6 to 6.5. Test the soil six months to a year before you plant to give yourself enough time to modify the soil pH or add nutrients, if required. For more information about soil testing, see Laboratories Serving Oregon: Soil, Water, Plant Tissue, and Feed Analysis (EM 8677), Soil Sampling for Home Gardens and Small Acreages (EC 628), and Soil Test Interpretation Guide (EM8713). If the soil is too acidic (the pH is too low), add lime to the soil as recommended by the soil analysis to raise the soil pH to the upper end of the ideal range for the berry crop. See Applying Lime to Raise Soil pH for Crop Production—Western Oregon (EM 9057) for more information. In general, if your soil pH is too low for berry production, incorporate finely ground dolomitic limestone at a rate of approximately 5 to 10 pounds per 100 square feet (1.1 to 2.1 ton per acre). You may also use high pH composts to add organic matter and increase soil pH (see Growing Berries on the Oregon Coast: An Overview (EM 9177). These amendments should be incorporated about a year prior to planting as it takes time for the soil pH to adjust after the addition of lime. See Table 1 for soil nutrient ranges for blackberries.
Raspberries are very sensitive to poor drainage. Because of their large root system, raspberries benefit when planted in well-drained soil that is at least 2 (and ideally 3) feet above the water table. Usually, raised beds are required to grow raspberries to ensure adequate drainage. Blackberries, on the other hand, are more tolerant of heavier soils and usually don’t need to be planted in raised beds. Ideally, provide a well-drained, fertile, loam soil with some water-holding capacity. This will ensure your raspberry and blackberry plants will be more vigorous and produce more fruit, regardless of type or cultivar. More detailed information on drainage and options for improvement is available in Growing Berries on the Oregon Coast: An Overview (EM 9177).
All blackberry cultivars are self-fruitful, so only one cultivar is necessary for pollination and fruit production. Trailing types have berries that are oblong with small seeds and intense, aromatic flavor. Erect types produce firmer fruit with larger seeds and less flavor and aroma. Semierect types produce high yields of late-season fruit with similar qualities to the erect types. Blackberry-raspberry hybrids are managed like trailing types. Many of these cultivars, however, need a warmer or more protected site for consistent fruit production. See Table 2 for recommended cultivars for each type of blackberry. For cultivar descriptions, see Blackberry Cultivars for Oregon (EC 1617).
Purchase certified disease-free plants from a reputable nursery. Blackberry plants are most commonly sold as potted plants propagated using tissue culture. Begin planting as soon as you can work the soil in the spring. Plant to a similar depth as the potting medium. Cover the planting hole with soil and firm the soil to remove air pockets. Small, tissue-cultured plants need to be cared for in the same way as a tender vegetable transplant (Figure 1). Water them frequently until the plants are established. Larger, potted plants are a little less tender, but good water management is still important.
Trailing and semierect blackberry plants should be grown as individual plants because they do not produce new primocanes from the roots. Space trailing plants 3 to 5 feet apart in the row and semierect plants 5 feet apart. Rows should be 10 feet (trailing types) to 12 feet (semierect types) apart. Erect blackberry plants are most commonly grown in a hedgerow. Space plants 2.5 to 3 feet apart in the row with 10 feet between rows. Keep any primocanes that emerge in the row area between plants. Maintain the row width to about 12 inches by pruning or rototilling to remove any primocanes that emerge outside this area. If you allow wider hedgerows, management tasks such as weeding, pruning, and harvest can be difficult, and disease can become more of a problem due to the dense canopy.
Only primocane-fruiting types of blackberries will produce a small crop in the planting year. All types will produce a “baby” crop the next year, and the third year they will be in mature production.
Although you can grow erect blackberries without support, trellising is beneficial to all types because it helps prevent cane breakage from wind, keeps the planting neater, and simplifies cultivation and harvesting.
Blackberries are extremely vigorous and most cultivars are floricane-fruiting. For these reasons, blackberries are less easily grown in containers.
Blackberry plants, like all berry crops, need adequate water to thrive. You can irrigate your crop by hand, or with sprinklers or drip systems — whatever works best for you. The important thing is to make sure that adequate moisture is getting to the root zone. For more information on irrigation, see Growing Berries on the Oregon Coast: An Overview (EM 9177).
In all berry cropping systems, drip irrigation is ideal. Blackberries can be irrigated with a single line of drip irrigation per row with half-gallon emitters placed every 18 inches. Established blackberry plants typically need from 1 to 1.5 inches of water per week during the growing season.
A mulch can help control annual weeds, conserve soil moisture, and depending on the type of mulch, provide a source of nutrients. Be careful to not bury the blackberry crowns as this can lead to crown rot or plant death. Deep straw is not recommended as it can bury the crown and lead to increased vole or rodent activity, which can damage the plants. For more detailed information on mulches, refer to Growing Berries on the Oregon Coast: An Overview (EM 9177).
When fertilizing new plantings, plan to divide the total required nitrogen (N) into three equal portions, the first starting two weeks after planting, the next one a month later, and the last a month after that. Spread the fertilizer evenly down the row area. Fertigation can also be used in blackberries. See the Caneberry Nutrient Management Guide (EM 8903) for more information.
In erect blackberries, fertilize with 2 ounces N per 10 feet of row (60 pounds N per acre). For semierect and trailing blackberries, apply 1 to 1.4 ounces N per plant, depending on soil type and plant vigor.
Well-balanced fertilizers, such as 16–16–16, some similar types of inorganic fertilizer, and some organic products, work well for blackberries. See Growing Berries on the Oregon Coast: An Overview (EM 9177) for more information on fertilizing berry plants.
Fertilize floricane-fruiting blackberries with 1.5 ounces N per plant or 3 ounces per 10 feet of row (80 pounds N per acre) per year. Fertilize primocane-fruiting blackberries with 3 ounces N per 10 feet of row (80 pounds N per acre).
Divide the fertilizer into two applications, applying the first in late March to early April, just as the new primocanes start to grow, and the other in late May to early June. Semierect and primocane-fruiting blackberries may require an additional 0.5 ounce N per plant or about 1 ounce per 10 feet of row (25 pounds N per acre) in mid- to late July to ensure there is adequate nutrition to accommodate the late- fruiting period.
Broadcast the fertilizer over the soil surface in the row area (about 2 to 3 feet wide, centered on the row). Irrigate immediately after fertilization. If you use manure applications (generally in autumn or early winter to a depth of about 2 inches), try reducing the fertilizer N by half and monitor plant growth to see if additional fertilizer N is needed. Fresh manure is not recommended as it is high in salt content and can burn plants.
If N is fertigated, divide the total recommended rate into equal amounts and make weekly or bi-weekly applications from early April through July, depending on the type of blackberries grown.
A well-managed plant should have healthy green leaves with good primocane growth (a good number per plant and a normal length for the cultivar being grown). Pale green or yellow primocane leaves could indicate N deficiency. Primocanes that are too tall (e.g., 10 feet for raspberry), thin (less than 0.37 inch), or with long internodes (distance between leaves) indicate an excess of N fertilizer.
Monitor soil pH every few years and add lime in autumn to maintain the soil pH within the desired range for raspberries and blackberries.
Blackberries are self-fruitful, so only one cultivar is necessary for fruit production. In many home gardens and on small farms, there are often sufficient native honey and bumble bees to ensure good pollination. However, for good fruit set in larger plantings, place two to four hives per acre in a location that will ensure good bee activity. Keep in mind that pollination is affected by wind. Place hives in the field no earlier than when, on average, 5 to 10 percent of each plant is in bloom. For more information, see Nurturing Mason Bees in Your Backyard in Western Oregon (EM9130) and Evaluating Honey Bee Colonies for Pollination (PNW 623).
Pick regularly. This not only helps ensure you collect berries at their optimal ripeness but also reduces insect pests and diseases that are more prevalent on overripe fruit. During periods of hot or rainy weather, you may need to pick more frequently. Try to avoid picking when fruit are wet from dew, fog, or rain and don’t wash it before storage. Wet fruit will decay faster. Refrigerate fruit immediately for optimal length of storage and quality.
Blackberries are easy to pick when they are fully ripe. Use a gentle breaking motion, by moving fruit up or down (Figure 2). Most cultivars change from a full shiny, black color to a dull, black color when fully ripe. Shiny black fruit are high in acid with comparatively less flavor and sweetness than dull black fruit. In general, harvest blackberries every 4 to 7 days, depending on the cultivar and weather. Pick into shallow containers so fruit does not crush.
Trailing cultivars will yield 10 to 13 pounds per plant (4.5 to 5.5 tons per acre), erect types will yield 18 to 28 pounds per 10 feet of row (4 to 6 tons per acre), and semierect types will yield 25 to 35 pounds per plant (10 to 15 tons per acre).
In the first growing season of trailing blackberries, primocanes should be trained to the trellis as they grow. Bundle them together and use twine to attach them straight up to the top wire; wrap them around the two wires, spreading out the canes, if they grow taller. These are the canes that will produce fruit the next year. In all subsequent years, plants will have fruiting canes (floricanes) trained on the wire that flower in the spring, and new primocanes will begin growing. In most trailing cultivars, the primocanes will “flop” over once they are about 3 feet long and will continue to grow along the ground through the season. Train these primocanes in a narrow bundle underneath the floricanes (Figure 3A) so they are out of the way and are not damaged as they grow. You may use wire hoops or stakes to keep the primocanes from being damaged between rows. Training will be easier if all of the primocanes from each plant are trained in the same direction so they are less tangled with those from the adjacent plants. Tipping trailing blackberry primocanes during the growing season will encourage branching and will not result in an increase in yield.
Remove the dying floricanes by the end of August and train the new primocanes onto the trellis. Train by dividing the primocanes from each plant into two bundles. Loop half the canes in one direction from the upper to lower trellis wires, bringing them back towards the plant with one or two twists; loop the other half in the opposite direction (Figure 3B). It is nearly impossible to train the long primocanes without damaging or kinking some canes during the process; however, taking care during training will improve yield. Secure the canes to the trellis using bailer’s twine or ties, if needed. Remove canes that are too short. In colder, higher-elevation sites or in areas with high wind, leaving the canes on the ground and training in February, well before bud break, may be of advantage so that canes are not exposed to colder temperatures or high winds during winter.
For summer-bearing erect blackberries, canes may trail along the ground the first year. Don’t worry; this is normal, and the canes will become stiffer as the plants age. Once plants are in their second growing season, prune primocanes and floricanes as described below.
The primocanes of erect blackberries require summer pruning for good yield. Tip the primocanes in late spring or early summer by removing the top 3 to 4 inches. Top them to a height of about 3 to 3.5 feet. You will need to go over the planting multiple times throughout early summer to catch all of the primocanes. These types produce productive lateral branches when they are topped. These cultivars will send up primocanes (suckers) outside of the hedgerow. The suckers should be treated as weeds and removed as they emerge, keeping the hedgerow no wider than about 12 inches.
In winter, prune out the dead floricanes and shorten the lateral branches on the primocanes to about 1.5 to 2.5 feet long (Figure 4). In larger plantings, this can be done by mechanically hedging the rows using sickle bars.
If you have the space, it is best to grow primocane-fruiting blackberry cultivars only for the primocane crop and other types for the floricane crop. Producing a floricane crop on these cultivars reduces and delays the primocane crop, making it too late for much of the fruit to be harvested prior to autumn rains or frost. To produce a primocane-only crop, remove all canes by cutting them just above ground level in late winter. Remove the top 6 to 12 inches of the tip of each new primocane when they are 3.5 feet tall. The lateral branches will flower and fruit in the fall (Figure 4). These benefit from a temporary or permanent T-trellis in most regions to prevent the canes from breaking in the wind.
Semierect blackberry cultivars are summer-pruned, similar to erect blackberry cultivars. Remove the top 2 to 6 inches of the primocane tip when the cane is just over 4 to 5 feet tall. This will encourage lateral branches and increase yield the following year. You will need to check the planting several times to ensure you have tipped all of the primocanes.
In winter, remove the dead floricanes. Train the primocanes to the wires of the trellis being used. You can shorten the lateral branches if they are too vigorous and if training the longer branches is difficult; this often leads to increased berry size.
Weeds compete with the berry plants for water, nutrients, and light, so it is important to keep weeds out of the row. A mulch layer of sawdust or bark can help control weeds, particularly annual ones.
In trailing and semierect blackberries, you can use a perforated, polyethylene ground cover (“weed mat”) as a mulch for weed control in the row (Figure 5). This type of mulch doesn’t work well in erect blackberries that produce primocanes from the roots because the weed mat inhibits new primocane growth. Install the weed mat prior to or just after planting by placing it over the row or raised bed and overlapping the edges. Stake down the edges or use soil to hold them down. Cut an “X” or a 6–inch-diameter circle in the plastic where each plant will be set, and plant through the holes. You can also lay down the weed mat just after you plant, feel for the plants under the plastic, and then to carefully cut the holes. Even though weed mat is perforated, it is best to use drip irrigation underneath it to ensure plants get enough irrigation water, particularly when grown on raised beds.
For chemical weed control, check with your county office of the OSU Extension Service or a garden or farm supply store for herbicides registered for use on blackberry plantings. Not all herbicides are registered for all crops.
You will also want to manage weeds between the rows (the aisles) so that they do not spread into the area with your berry plants. The aisles can be cultivated and kept as bare soil or seeded with grass or another cover crop. If you are growing relatively few berry plants in your home garden, you may find it more practical to use other materials between your rows, such as bark mulch, wood chips, or straw. See Commercial Red Raspberry Production in the Pacific Northwest (PNW 598) for more detailed information on using cover crops in berry production systems.
Refer to the PNW Plant Disease Management Handbook for more detailed information on weed control and specific weeds.
The most important insect pest in berry production is the spotted wing drosophila (SWD; Drosophila suzukii). It was introduced to the mainland United States in 2008 and has rapidly become a major problem in all berry crop production areas. This vinegar fly looks like a commonly seen fruit fly. However, the female lays eggs in developing fruit (generally after it first develops some color). The resultant larvae feed inside the berry while the fruit are ripening. Populations of SWD build up during the season, so late-fruiting cultivars (erect and semierect blackberry and primocane-fruiting cultivars) are more prone to this pest. For more information on how to control and manage this insect, refer to the SWD publications listed under “For more information.”
Check with your local office of the OSU Extension Service for control recommendations if insects become a problem. Control methods are also outlined in the PNW Insect Management Handbook. Control options vary for commercial small-acreage farmers (with commercial pesticide applicator’s license) and home gardeners.
The most important insect problems for blackberries are leaf roller larvae, raspberry crown borer, and red berry mite (late-fruiting cultivars).
Control methods are outlined in the PNW Plant Disease Management Handbook. Control options vary for commercial small-acreage farmers (with commercial pesticide applicator’s license) and home gardeners. Check with your local office of the OSU Extension Service for control recommendations if diseases become a problem.
Common blackberry disease problems include cane and leaf spot, yellow rust, anthracnose, and fruit rot.
To learn more about growing individual berry crops on the Oregon Coast, see these other publications in the series: