Fertilizing Blackberry Plants – Learn When To Fertilize Blackberry Bushes

Fertilizing Blackberry Plants – Learn When To Fertilize Blackberry Bushes

By: Amy Grant

If you want to grow your own fruit, a great place to start is by growing blackberries. Fertilizing your blackberry plants will give you the highest yield and the largest juiciest fruit, but how to fertilize your blackberry bushes? Read on to find out when to fertilize blackberry bushes and other specific blackberry feeding requirements.

How to Fertilize Blackberries

Berries, in general, are nutritious, and blackberries have been shown to help fight cancer and cardiovascular disease as well as slow down aging of the brain. Today’s new cultivars can even be found thornless, erasing those memories of torn clothing and scratched skin while harvesting their wild brethren.

Easier to harvest, they may be, but to get that bumper crop, you need a fertilizer for blackberries. First things first, though. Plant your berries in full sun, allowing plenty of room to grow. The soil should be well-draining, sandy loam rich in organic matter. Decide if you want trailing, semi-trailing or erect berries and thorny or thornless. All blackberries benefit from a trellis or support so have that in place as well. How many plants should you get? Well, a single healthy blackberry plant can supply up to 10 pounds (4.5 kg.) of berries per year!

When to Fertilize Blackberries

Now that you have planted your selections, what are the feeding requirements for your new blackberries? You don’t begin fertilizing blackberry plants until 3-4 weeks after the setting of new plants. Fertilize after growth starts. Use a complete fertilizer, like 10-10-10, in the amount of 5 pounds (2.2 kg.) per 100 linear feet (30 m.) or 3-4 ounces (85-113 gr.) around the base of each blackberry.

Use either a complete 10-10-10 food as fertilizer for your blackberries or use compost, manure or another organic fertilizer. Apply 50 pounds (23 kg.) of organic fertilizer per 100 feet (30 m.) in the late fall prior to the first frost.

As growth starts to appear in early spring, spread inorganic fertilizer over the top of the soil in each row in the amount as above of 5 pounds (2.26 kg.) of 10-10-10 per 100 feet (30 m.).

Some folks say to fertilize three times a year and some say once in the spring and once in the late fall before the first frost. The blackberries will let you know if you need a supplemental feeding. Look at their leaves and determine if the plant is fruiting and growing well. If so, no fertilizing the blackberry plants is necessary.

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How to Fertilize Blackberry Bushes

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Blackberries are easy to grow and delicious to eat fresh. Or, maybe you'd like to make your own blackberry jam. Blackberries do best in U.S. Department of Agriculture hardiness zones 4 through 10. According to The American Society for Horticultural Science, blackberries don't require a high level of nutrients compared to some other fruits, but you may still need to offer them a boost as the plant grows. For best results, know when to fertilize, what fertilizer to use and how to fertilize blackberry bushes properly.

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How to Grow the "Kiowa" Blackberry

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The “Kiowa” blackberry (Rubus x "Kiowa") produces large, glossy fruits for up to six weeks in the summer. The canes reach up to 6 feet tall with a spread up to 8 feet. The “Kiowa” blackberry originated at the University of Arkansas in 1983 from a cross of two varieties, the Ark. 791 and Ark. 1058. The species became publicly available in 1996. It gained popularity due to its large berries and erect growing habit that doesn't require trellising. Blackberries (Rubus spp.), native to North America, grow in U.S. Department of Agriculture plant hardiness zones 4 through 9. With care, blackberries produce abundant fruits for years.

Choose a site for growing blackberries. Locate the site at least 300 feet away from raspberry plots. The site needs well-drained, sandy loam and full sun for the best fruit production.

Test the soil pH using a kit. “Kiowa” blackberries need a pH range of 5.5 to 7.0.

Amend the soil as needed. Use sulfur to lower the pH and lime to raise it. Spread it on the soil. Spread a 4-inch layer of compost on the soil to improve drainage. Till or cultivate the amendments to about 12 inches deep.

Plant “Kiowa” blackberries 2 to 4 feet apart in rows spaced 8 feet apart. Place bare-root plants in holes just big enough to accommodate the roots when spread. Place potted blackberries in holes twice as wide as the planter. Keep the planting depth the same as the original plants.

Back-fill the planting holes halfway. Fill the hole with water, and allow it to drain. Finish filling the hole with the dirt, and tamp it down.

Spread a 4-inch layer of mulch, such as bark mulch or compost, in the blackberry bed. The mulch prevents weeds, an important factor in growing “Kiowa” blackberries, because weeding around the thorny canes proves difficult. Mulch also preserves soil moisture levels. Renew the mulch every spring.

Tip first-year canes at about 3 to 4 feet tall in the spring to encourage bushier growth. Blackberries produce fruit on floricanes, or 2-year-old canes. Cut the canes to ground level after fruit production.

Provide 1 to 2 inches of water every week during the growing season from May through October. Water two times a week, or more during drought. Water at the base of the plants, or use a drip irrigation system to prevent disease and fruit rot.

Broadcast 5 pounds of 20-20-20 fertilizer for every 100 feet of row yearly in early spring. Alternatively, apply 50 pounds of compost or manure per 100 feet of row in early winter.

Insect problems on blackberries are minimal. Pests like aphids, Japanese beetles and spider mites can be controlled on an as-needed basis with general pesticides. Crown borers can be a serious pest. Chemical controls are not available. Diseases include rusts, fruit rot and “double blossom.” Control fruit rots with a sound fungicide program. Rosette, or “double blossom,” is a disease that causes the shoots to have a bushy, broom-shaped appearance on the tips. These shoots produce abnormal blossoms that will not mature to fruit but will produce spores that infect the new primocanes. Again, fungicides can be used in a preventive spray program. If severe infection occurs, summer mowing of all canes down to the ground will reduce infection of later emerging primocanes. Leaf and cane diseases are controlled by the use of copper, lime sulfur or Bordeaux. Apply all chemicals according to directions on the label.

Many varieties of blackberries are available to the homeowner. Some of these are listed in the table below.

Blackberry Varieties for South Carolina

Variety Area¹ Cane Type Comments
Choctaw All Erect Thorny early blooming early ripening cultivar with good flavor smaller seeds than other varieties rosette resistance unknown.
Brazos SR,CP Erect Thorny soft fruit yields well in the lower part of SC very susceptible to rosette disease.
Rosborough P,SR,CP Erect Thorny productive release from Texas slightly acid fruit moderately susceptible to rosette disease.
Cheyenne All Erect Thorny slightly tart very good producer (especially in the lower part of the state) susceptible to rosette disease.
Cherokee All Erect Thorny fairly sweet good producer (especially in the upper part of the state) very susceptible to rosette disease.
Arapaho All Erect Thornless ripening begins 11 days before Navaho medium sizefruit better primocane production than Navaho disease resistance unknown.
Shawnee All Erect Thorny late blooming and heavy producer ripens later than most thorny erect types and over a long period of time very susceptible to rosette disease.
Navaho All Erect Thornless late ripening for erect blackberry medium size fruit primocane production may be poor leaf spot problems very susceptible to orange rust rosette resistance is good.
Kiowa All Erect Thorny very large and sweet berry long ripening period moderately resistant to anthracnose and rust unknown reaction to rosette.
Gem P,SR,CP Semi-trailing Thorny excellent quality good producer resistant to rosette disease.
Thornless Boysenberry P,SR,CP Semi-trailing Very good quality production only fair.Boysenberry
Black Satin All Semi-trailing Thornless fair quality good producer.
Hull All Semi-trailing Thornless better quality than Black Satin ripens late June to early July vigorous and relatively disease-free.
¹Area: M=Mountains P=Piedmont SR=Sandhills and Ridge CP=Coastal Plains All=Entire State

Excerpted from the South Carolina Master Gardener Training Manual, EC 678.

If this document didn’t answer your questions, please contact HGIC at [email protected] or 1-888-656-9988.


David Parker, Retired Clemson Extension Agent, Clemson University
Greg Reighard, PhD, Extension Fruit Specialist, Clemson University

This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.

Blackberries are produced on the canes of a perennial shrub. 'Arapaho' is a thornless, self-supporting blackberry and the following instructions are for this upright kind of blackberry. The roots live for more than two years and the canes take two years to finish their lifecycle. During the first year, the canes sprout and grow to their full height. Canes are produced from both the roots and the crown. They go dormant for the winter. In the second year the canes leaf, flower, and fruit. At the same time the roots are producing new first-year canes. After fruiting, the second-year canes die and must be be removed.

Site Selection for Blackberry Bushes

Light: Full Sun

Soil: Prefer acidic to slightly basic (6.0-7.0), well-drained, organic soil. However, they adapt to most soil types except alkaline and wet. If you have clay soil, you will need to amend with organic matter. To increase the soil's organic content, amend with organic mulch-wet peat moss, well-aged sawdust, straw or leaf litter.

Pollination: Blackberries are self pollinating.

Hardiness Zone: 4-9

Minimum Chill Hours Needed: 400-500

Where to Plant: Blackberries tend to form thickets and are vigorously rooted. Locate the plants where you can control "volunteers. " Blackberries have long roots and send up suckers many feet from the parent plant. Leave room to mow around the beds.

Do Not Plant: In established garden areas where you have previously planted vegetables or fruit plants. Plant blackberries 300 feet away from raspberries.

Trellis Support Not Needed: 'Arapaho' blackberries do not need a trellis for support. However, they can be trained to a trellis no higher than 6'-8'.

How to Plant Blackberry Bushes

For best results, plant your blackberry bushes in early spring. Once your plants arrive, plant them immediately. If you cannot plant immediately, keep new arrivals cool and roots moist. To keep cool, it is recommended that you store in refrigerator or cool place.

  1. Unpack and Soak: Unpack blackberry and soak in water for 3 to 6 hours just before planting.
  2. Cut Broken Roots.
  3. Cover Roots: Cover roots from sunlight when planting. Blackberries have a high mortality rate when roots are exposed to sunlight while planting.
  4. Dig Hole(s): The width of the hole should allow you to spread roots. If you are planting multiple blackberries dig holes 2'-4' apart. If you are creating several rows, dig holes 6'12' apart.
  5. Spread Roots in Hole.
  6. Shovel Dirt Back in Hole and Add Amend Soil.
  7. Water: Give each plant 1"-2" of water. The plants are rather shallow rooted, so moisture needs to be at the surface. Do not let soil become dry to a depth of 6".
  8. Add Fertilizer: A weak liquid nitrogen fertilizer may be applied at planting. Keep fertilizer 3"-4" away from the base of the plant to avoid burning the roots.
  9. Mulch: Mulch the first year to keep the weeds down and increase the crop yield, but do not mulch after that unless the soil is very sandy.

How to Water Blackberries

First three weeks watering schedule: Water blackberries plants during the day. Water more frequently for 2-3 weeks after planting. As a rule of thumb, the top inch of soil is moist during the first 2-3 weeks.

Watering after first three weeks: Water blackberries plants during the day. Then, give them about 1"-2" per week during growing season and up to 4" per week during harvest. The plants are rather shallow rooted, so moisture needs to be at the surface. Do not let soil become dry to a depth of 6".

How to Prune Blackberries

First Year Pruning: First year erect canes should be left unpruned.

Annual Pruning after First Year: Hand-held clippers are necessary when pruning. First year erect canes should be left unpruned. Second year canes should be pruned back to 40"-48". Pruning encourages lateral branching and increases cane strength, so they don't fall over in snow and wind. Pruning should be done early in the growing season to decrease wounds that cause cane blight. Lateral branches should be cut back to 12"-18".

During the second year, remove damaged, weak and rubbing canes. You should thin out healthy canes closer than 6" apart. Any pruned or removed canes should be disposed to eliminate the spread of disease and insects.

How to Fertilize Blackberry Bushes

1st Year Fertilizing: After the soil has settled, add 10-10-10 nitrogen fertilizer. You can purchase 10-10-10 nitrogen fertilizer at your local garden store.

Fertilizing after 1st year: Add actual nitrogen or a 10-10-10 nitrogen fertilizer, a higher amount added in the second year. When spreading the fertilizer, keep it several feet away from the base of the plant to avoid burning the roots.

How to Pick Blackberries

Harvest: It takes about three years to achieve a full crop of berries. After the berries turn shiny black, wait a few days to let them soften and lose their shine. Now they will be at the peak of sweetness for picking, When ripe, the berry will detach easily. Harvesting in the morning on cool, dry days will result in a longer shelf-life. Put in shallow containers to avoid crushing and move out of the sun. In very warm areas, blackberries may turn red and become bitter if exposed to excessive sunlight. Avoid extra handling of the berries and refrigerate. Do not wash the berries until ready to use them. Blackberries have a longer shelf life than raspberries about 4-5 days. Blackberries will stain clothing, so wear old or dark clothing when picking.

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