Key management points for cold-frame peaches in the Beijing-Tianjin region around the Spring Festival

1. Frame-covering period

Because cold-frame peaches have no cold-protection facilities and rely solely on sunlight for warming and the frame film for insulation, the day-night temperature difference is large. The frame-covering period should preferably be around February 20, so that the flowering period is March 25-31 and the peach ripening period is early June, 10-15 days earlier than open-field peaches.

For heated cold-frame peach sheds, install 1 heater per 350-450 sq m at the center of the cold frame, burning wood or coal; the gas is discharged outside the frame through the chimney in the middle of the stove, and the air is preheated through the stove's interlayer and then blown as hot air to the north and south through the chimneys on both sides. Alternatively, install 3 stoves on each side of the frame, each stove with 6 sections of chimney, with the gas discharged outside the frame on both sides. For heated cold-frame peaches, the frame-covering period should preferably be February 2-4, the flowering period is March 15-31, and the ripening period is May 25-31, about 20 days earlier than open-field peaches.

2. Management after covering the frame

Temperature regulation before flowering. After covering the frame, pay attention to ventilation during the day; when the temperature is below 20°C, no ventilation is needed. Always pay attention to patching frame cracks and holes. A 3 m high windbreak must be built on the north side of the frame to help with wind protection and insulation. The period from frame covering to flowering should preferably be 35 days. The frame temperature must be raised gradually: in the first week after covering the frame, maintain 10-18°C during the day, with a maximum not exceeding 20°C; in the middle period, maintain 12-20°C during the day, with a maximum not exceeding 22°C; and 15 days before flowering, maintain 14-23°C during the day, with a maximum not exceeding 25°C.

Film mulching and watering. 3-5 days after covering the frame, lay 1.5 m wide plastic film between the peach trees. About 10 days after covering the frame, when the soil is about to thaw, water appropriately; too much water can lower the soil temperature excessively.

Pest and disease control. During the flower bud swelling stage, spray 3 degrees Baume lime sulfur mixture once. This spray must be applied finely and evenly.

Re-pruning before flowering. Flower buds are easy to identify during the swelling stage. First, cut out large and vigorous branches with no flowers or few flowers on the upper and outer parts of the canopy; second, thin out overly dense branches and thin weak branches in the middle and lower parts; third, lightly cut back moderately the long spurs left unpruned, while leaving all other fruiting branches unpruned without heading back, and after fruit set, moderately cut back to improve ventilation and light penetration, balance tree vigor, and increase the fruit-setting rate.

3. Flowering period management

Aphid control. At the bud stage, when individual flower buds show red, spray imidacloprid 3000-fold solution + mancozeb 800-fold solution once. Spray evenly and thoroughly to kill green peach aphids and pathogens.

Temperature regulation during the flowering period. The frame temperature during flowering must not be too high; maintain 14-22°C during the day, and do not exceed 25°C at most. Cool down by opening the central seam, both shoulders, and the north and south doors for ventilation. At 3-4 p.m., when the frame temperature reaches 20°C, the vents should be closed. At 12 p.m. at night, if the frame temperature is below 5°C, light the stove immediately to raise the temperature until 7 a.m. to prevent flower and fruit freezing.

Pollination during the flowering period. From the early flowering stage to the full flowering stage of frame peaches, manually hand-pollinate only individual trees with few flowers twice, then around 11 a.m. when there is no dew, pollinate by blowing air 4 times. Practice has shown that artificial air-blow pollination gives good fruit set, is simple, fast, and labor-saving. If there are few pollinizer varieties for frame peaches or the pollinizer varieties are too concentrated, collect pollen first and then hand-pollinate to prevent low fruit set and reduced yield. At the full flowering stage, spray 20 ml/L gibberellin + 0.3% urea solution + 0.3% borax solution once, and at the end of the full flowering stage spray 0.3% monopotassium phosphate solution once more, which can significantly increase the fruit-setting rate.

Control excessive new shoot growth. As the frame temperature rises, 15 days after flowering, except for weak peach trees, all should undergo trunk girdling, and after an interval of 8-10 days, girdle the trunk once more to retain nutrients in the tree and promote fruit set. For peach trees that still grow vigorously after two trunk girdlings, spray paclobutrazol 150-fold solution once more.

4. Strict fruit thinning

Fruit thinning should be carried out in 2 rounds. The first fruit thinning should be 1 week after flower drop, first removing diseased and damaged fruit, small fruit, and twin fruit; the second should be about 25 days after flowering for final fruit set. When thinning, vigorous trees and vigorous branches can retain appropriately more fruit, while weak trees and weak branches should retain less fruit. In specific fruit retention, the guideline is to retain 3-5 fruit on long fruiting branches, 2-3 fruit on medium fruiting branches, and 1 fruit on short fruiting branches. In addition, the upper and outer parts of the canopy have good light, large fruit, and good coloration, so appropriately more fruit can be retained there, while fewer fruit should be retained in the inner canopy and lower parts.