Blackberry

Blackberries (Rubus fruticosus) are incredibly productive when managed properly.
Rob Last, ©2023, Clemson Extension

Blackberries (Rubus fruticosus) are native to the Southeastern United States and can be found growing wild in many areas throughout South Carolina. They are highly valued by wildlife and humans alike. Cultivated blackberries have been bred for desirable traits that make them less thorny, bigger, sweeter, and more productive.

Blackberries are divided into classes by their growth habit and are described as trailing, semi-trailing, or erect. Blackberries produce biennial shoots from their crown. The first-year shoot is the primocane, and the second-year shoot is known as the floricane. Many blackberry varieties are considered floricane producing, producing fruit only on the second season’s growth.

In recent years, breeding efforts have yielded varieties of blackberries that produce fruit on both primocane and floricane shoots. These varieties are commonly called primocane varieties. In most areas of the state, gardeners can enjoy fruit in the spring from the floricanes and fruit in the late summer or fall from the primocanes, yielding two crops yearly. Primocanes will have five leaflets, and floricanes will have three leaflets.

Site Selection & Planting

Blackberries should be planted in well-drained soils with a pH in the 6.0-6.5 range. Soil testing should be performed four to six months before establishing blackberries to ensure ample time for soil amendments, such as lime or sulfur, to work. Amend each planting hole with a mix of compost and native soil. Blackberries should be planted in full sun for optimal plant health and production. Blackberries should not be planted in part-shade to shaded areas as they will harbor more diseases and never produce good yields. If possible, rows should be oriented north to south so that both sides of the blackberry plant will receive even sunlight, ensuring maximum production and ripening of the fruit.

Semi-trailing varieties should be planted 6 to 8 feet apart in the row, with rows 10 feet apart. Erect varieties should be planted 2 to 4 feet apart in the row and 10 feet between rows. Plant blackberries in early spring, about 4 to 6 weeks before the last frost. When planting, ensure the crown is about 2 inches below the soil line and carefully spread the roots. When planting root cuttings, place the cuttings in a horizontal position and cover 4 to 6 inches deep in sandy soils or 3 to 4 inches deep in clay soils.

A V-trellis system trains canes to get maximum sunlight and good airflow.
Zack Snipes, ©2020, Clemson Extension

Trellising 

Blackberries benefit greatly from trellising. Trellising helps to prevent disease, keeps fruit from rotting, and gives a tidy appearance to the garden. The most common type of trellis system is the V-trellis system. This system uses 8-foot T-posts driven into the ground at 20-to-30-degree angles. The posts are driven into the ground in pairs every 20 to 25 feet. At the end of the row, a wooden post or another T-post is used as the anchor of the trellis. Two rows of 14 gauge, high-tensile wire are used at two- and five-foot heights, respectively. The wire will help hold up and stabilize the canes as they grow. The V-trellis system allows maximum airflow and sunlight capture for the blackberries.

Other trellising systems, such as the hedge row (I-trellis) and T-trellis, are also options for gardeners. These trellis systems are built on the same basic principle of the V-trellis but resemble an “I” or “T” shape in their design rather than the “V.”

Mulching & Watering

Commonly used mulches for blackberries can include landscape fabric, polyethylene mulch, wood chips, or pine straw. Mulch aids in water retention and can provide some weed control. Though blackberries are drought-tolerant, they require considerable water during the establishment and fruiting period. Apply about 1 inch of water per week by irrigation if rainfall does not meet the need.

Fertilization

Fertilize blackberries in early spring when growth starts and again just after harvest. A soil test will provide recommendations for fertilization at the planting site. Apply the fertilizer in a 12-inch circle around the plant during the first year or two of growth. On older plants, broadcast the fertilizer down the row. A tissue analysis may need to be collected during the season to determine if blackberry plants have proper nutrition.

Blackberries should be tip-pruned periodically throughout the year to increase production.
Zack Snipes, ©2023, Clemson Extension

Pruning & Training

The first step in pruning blackberries is to understand their growth cycle. Blackberries have crowns that produce biennial shoots, meaning they live for two years and then die. During the first year of growth, the shoots are called primocanes. These primocanes develop flower buds in the first year of growth. In the second year, the shoots are called floricanes. These floricanes produce flowers that mature into fruit. After fruiting, these floricanes die and should be removed.

Prune out and discard dead, diseased, or weak floricanes during the dormant season. It will be obvious which canes are the dead floricanes. Thin primocanes to 3 to 6 vigorous shoots.

The lower 14-gauge wire in the trellis system will shape the blackberry plant, while the top wire will support the canes. Loosely tie shoots and older canes to the top wire.

Erect varieties do not need support if the primocanes are pruned during the summer to keep the canes from growing more than 3 to 4 feet tall. When the new shoots are 30 to 36 inches tall, cut off the tips to promote branching. Following harvest, cut and remove all floricanes. Continue to tip primocanes at this time. During the winter, prune the laterals to 12 to 14 inches for easier harvesting and larger berries.

Blackberries are ripe and at peak flavor when they lose their glossy shine and turn slightly dull.
Rob Last, ©2023, Clemson Extension

Harvesting

Blackberries are ripe and at peak flavor when they lose their glossy shine and turn slightly dull. Trailing and semi-trailing varieties begin to ripen in late June in the Piedmont, one to two weeks earlier in coastal areas and one to two weeks later in mountainous areas. Erect varieties are about two weeks earlier than trailing or semi-trailing varieties. Harvest should cover two to three weeks. If a more extended harvest is desired, select several varieties with different fruiting windows and try including at least one primocane fruiting variety.

For a longer shelf-life, harvest blackberries during the cooler part of the day. Harvest in dry weather when the plants and berries have dried from the morning dew. Once harvested, refrigerate berries to remove field heat. The faster the field heat is removed, the longer shelf-life the berry will have. Store berries in a breathable container with no more than a 2 to 3 berry depth. While harvesting, remove all soft or rotten berries from the plant and discard them. When the plant is kept picked and free of soft berries, it will return better and higher quality yields.

Stippling of the leaves is a classic symptom of spider mite damage on blackberry foliage.
Zack Snipes, ©2017, Clemson Extension

Problems

Pests that are commonly problematic on blackberries include aphids, Japanese beetles, stink bugs, spotted-wing drosophila, and spider mites. These pests can be managed as needed depending on the severity of their damage. Biological control and mechanical removal of these pests are often enough to minimize damage. Another insect management tool is removing fruit as they ripen and not leaving overripe fruit on the plant. Crown borers can be a serious pest and difficult to manage.

Blackberry diseases can be found on the crown, canes, foliage, or fruit. Crown diseases include crown gall and fusarium wilt. Cane diseases include Anthracnose cane spot, cane blight, cane rust, and orange cane blotch. Foliage diseases include blackberry yellow vein disease, leaf rust, downy mildew, orange rust, powdery mildew, Pseudocercospora leaf spot, rosette (double blossom), and Septoria leaf spot. Botrytis is the most common fruit rot.

Disease occurrence and severity can be reduced using sound cultural practices, such as proper site selection, cultivar selection, irrigation, fertilizer, applying fungicide, pruning, and periodic sanitation of diseased tissue and fruit. Preventative fungicides, such as copper and potassium phosphite products, can help prevent infections when used before the disease develops. If using pesticides, apply all chemicals according to the directions on the label. Once a disease develops, remove infected tissue from the garden and throw it away, reducing the spread of the disease.

Weeds need to be managed in and around blackberries. A weed-free strip 2 to 3 feet wide on either side of the blackberry row can reduce competition for water and nutrients. This weed-free strip can be achieved with a combination of methods. Mulches, flame weeders, and pre and post-emergent herbicides are all great options when maintaining a weed-free strip.

Variety Selection

Many varieties of blackberries are available for planting in home gardens (see table below). Older varieties with poor trellising habits, thorns, low disease and insect resistance, or less appealing taste are being replaced with newer varieties with more desirable qualities. Some examples of older varieties still available include Choctaw, Cherokee, Shawnee, Navaho, and Gem.

Recommended Blackberry Varieties for South Carolina

Revised by Zack Snipes 11/23

Originally published 09/99