Blackberry Cultivation Methods and Key Technical Points Explained

Blackberry, also known as dewberry, originated in North America and belongs to the Rosaceae family as a perennial vine of the genus Rubus. As far back as more than two thousand years ago in ancient Greece, the local people had already formed the custom of gathering and eating wild thorny blackberries. It is a representative variety of the third-generation fruit that has become popular worldwide in recent years, recognized by the Food and Agriculture Organization of the United Nations as a third-generation new special fruit, and also praised by European and American countries as the "fruit of life" and the "black diamond."

Planting Conditions and Methods

I. Field Planting

Plant along a north-south direction, with a spacing of 1m x 1.5m. Before planting, dig a trench 1 meter wide and 60~70 cm deep. Fill the bottom of the trench with 15~20 cm thick corn stalks, apply a small amount of urea, and calculate the fertilizer amount at a standard of 2500 kg of high-quality chicken manure per 667 sq m. Backfill with topsoil, water, and let it settle. In early April, dig holes in the planting trench 30 cm wide and 30 cm deep. Soak the seedling roots in 50 mg/LABT3 rooting powder for 5 minutes before planting, water, and cover with black mulch.

II. Fertilizer Management

In mid-September each year, apply 2,500 kg of high-quality chicken manure and 50 kg of nitrogen-phosphorus-potassium compound fertilizer per 667 sq m per year. During the rapid growth period of new shoots, apply 50 kg of urea per 667 sq m as a top dressing, and spray 0.2% urea once every 10 days, spraying three times. Spray 0.3% borax 3 to 5 days before flowering, and spray 0.2% to 0.3% zinc sulfate every 1-2 days, which can greatly reduce the proportion of small fruits. During the fruit enlargement period, apply 50 kg of diammonium phosphate. In addition, combined with pesticide spraying, spray 0.3% potassium dihydrogen phosphate or 500 times diluted photosynthetic micro-fertilizer, 800-1000 times diluted vitality solution every 10 days, and spray 3 times to supplement tree nutrition.

III. Training and Pruning 

Blackberry training techniques generally follow the grape trellis training method. When seedlings are planted in the same year, leave 3 to 4 new shoots growing vigorously. When the branches grow to 30-40 cm, tie them upward, and the rest will be cut from the base, and 3 to 4 main branches will form in the future. Cultivate 2 to 3 side branches on each main branch. Main branches are generally pinched at 1.0~1.2m, side branches are generally pinched when they grow to 50cm, and nutrient branches are generally pinched after retaining 5~7 leaves. At the early flowering stage, nutrient branches should be heavily pinched to reduce the consumption of tree nutrients, ensure consistent flowering, and make flowering neat. After harvesting the fruit, remove the fruiting branches from the base and cultivate new main branches and branches for the coming year. When pruning in winter, cut off aging main branches, diseased branches, thin branches, and dense branches. In the following year, retain the main robust branches. Usually, 9 to 12 side branches can be kept strong, and branch length should be controlled between 1.0 and 1.2 meters.

IV. Temperature and Humidity Management

Blackberries require 1000 hours at 7.2°C or lower to pass through natural dormancy. Therefore, in mid-November, the film should be fastened and straw curtains placed on it, so that there is no light in the greenhouse, and all vents are opened at night to regulate the greenhouse temperature to -2 to 7.2°C, which can increase low temperature and protect plants from frost damage. After about 30 days, it will gradually warm up in mid-December. During the day, 1/3 of the straw curtains are raised, and after 5 days, 2/3 of the straw curtains are raised during the day, and after another 5 days they are all lifted during the day.

From warming and sprouting, low-temperature management should be adopted in the first week, maintaining about 20°C during the day and 10 to 15°C at night, then gradually heating until bud break and sprouting, and it can rise to 28-30°C during the day and 15-20°C at night, with the minimum not lower than 5°C. This period is the period of greatest water demand during the blackberry growth period. It requires sufficient watering. Generally irrigate twice with 30mm of water, keep the greenhouse doors and windows closed, and maintain relative air humidity above 80%. If daytime humidity is low, spray water onto the branches to place them under a certain degree of high temperature and high humidity, promoting early bud development.

At the beginning of new shoot growth, implement low-temperature and low-humidity management. Control the daytime temperature at 25-28°C, nighttime at 15°C and at least 10°C. While strictly controlling irrigation, air humidity should also be strictly controlled and maintained at about 60%.

Before and after flowering, a higher temperature is required. During the day, it should be maintained at about 28°C, at night at 16-18°C, at least 15°C, and air humidity should be maintained at about 50%.

During the young fruit enlargement period, the daytime temperature should be maintained at 25-28°C, not exceeding 30°C; the nighttime temperature can be maintained at 18-20°C, but not exceeding 20°C. Humidity management can retain its nature.

When the berries are in the coloring and ripening stage, it is necessary to increase the day-night temperature difference and increase sugar accumulation, with daytime 28 to 30°C and nighttime 16 to 18°C or lower. Supplement light and add carbon dioxide gas fertilizer.

Insufficient light and poor light quality are common problems in winter-warm solar greenhouse cultivation of blackberries, so light must be supplemented. Supplement 1 hour per day before fruit set, and supplement 2h per day after fruit set. Fluorescent lamps can be used for supplemental light, with the lamp about 50cm from the tree body. 

V. Flower and Fruit Management

Two days before blackberry flowering, place bees in the greenhouse for pollination to increase the fruit set rate. Spray 0.5% borax plus 0.2% urea at the initial flowering stage; spray 5-10mg/L gibberellin plus 0.2% phosphoric acid during flowering. Both potassium dihydrogen phosphate treatments can increase the fruit set rate. At the same time, remove excessive flowers during flowering, and thin fruit 1 week after flower drop, with 20 to 30 fruits per cluster and no more than 40. To prevent fruit drop before harvest, 70mg/kg naphthalene acetic acid can be sprayed twice within 30 days before harvest, which can effectively reduce fruit drop.

When the fruit enters the blackening stage, all reflective film is placed on the greenhouse floor, which is beneficial for increasing ground temperature, reducing humidity in the shed, promoting fruit development, enhancing coloring, and making the fruit mature 6 to 8 days earlier. Spraying 0.5% glucose solution during the fruit enlargement period can significantly increase the sugar content of the fruit, reduce acidity, and improve fruit quality. Thin out vigorously growing new shoots in the upper canopy that seriously shade the fruit 10 days before fruit ripening, to facilitate fruit coloring. The treated fruit is large and well colored. The yield per 667 sq m should be controlled within 2000 kg, and the yield should be stable year after year.

VI. Pest and Disease Control 

Blackberries cultivated in greenhouses have relatively mild pests and diseases. Spray 5°Be lime sulfur mixture before sprouting. If there is gray mold and root rot, 1000 times diluted speedling or 50% carbendazim 500~800 times liquid can be used for prevention and control.