How Do Grapes in Northeast China Survive the Winter? A Detailed Guide to Cold-Protection and Overwintering Methods
The winters in Northeast China are cold. During grape growth, the minimum air temperature required is about 12°C-15°C, and the minimum soil temperature is about 10°C-13°C. So, how do grapes in Northeast China survive the winter?
1. Above-ground soil burial cold-protection method
Suitable for small plants with few canes; while the root system is unaffected, take soil from nearby and mound it over the plant. First, after pruning, lay the canes on the ground in their natural direction. For trellised canes, they can be tied into bundles with straw rope or similar. Then place soil pillows at the base of the canes to prevent them from being crushed and broken, and at the same time to increase cold protection for the root system. Finally, take soil from a distance of 1—1.5 m away from the root zone and mound it over the entire plant until it is well covered. The thickness of the buried soil depends on the local climate and soil conditions, as well as the cold hardiness of the cultivated variety and rootstock. Generally, in North China and similar areas, the buried soil thickness must be no less than 30 cm, and in colder regions it can be appropriately thickened.
2. Underground soil burial cold-protection method
Suitable for plants with more canes or older vines. First, after pruning, tie the canes well in their natural direction. They can also be tied into several groups according to the number of canes, and then a trench is dug in the same direction on the ground. The depth and width of the trench depend on the size of the cane bundles, and it is best if the canes can be fully or half placed into the trench. Generally, the depth is 30—50 cm and the width is 50 cm. Dig shallower near the root area to avoid damaging the roots. After placing the canes into the trench, take soil and cover them firmly; generally, 20—40 cm of soil is sufficient. If conditions permit, the canes can also be placed into the trench, wooden poles laid across above the trench, then a 10 cm thick layer of crop straw, leaves or dry grass added, and finally soil added in 2—3 rounds. Each round of soil covering should not be too thick; gradually increase the thickness of the buried soil as the temperature drops, which gives a better insulation effect.
3. Plastic film protection cold-protection method
Suitable for grapes in courtyards where digging trenches for cold protection is inconvenient. After pruning, the plants are tied and pressed to the ground in their natural direction, then covered with a 40 cm thick layer of sawdust, wheat straw, corn stalks or rice straw, etc. To prevent wind drying and air penetration, the outer layer is wrapped well with agricultural plastic film, and the surroundings are earthed up firmly. Note that during the cold-protection period, the plastic film should not be broken; otherwise, cold air entering can cause freeze damage.
4. Partial soil burial cold-protection method
Suitable for areas where the minimum winter temperature is not lower than -10°C and air humidity is relatively high, and for varieties with strong cold and drought resistance. When the grapes are not pruned in winter and not taken down from the trellis, build a 30—50 cm thick mound of soil at the base of the plant before the soil freezes, and prune in the following spring.
In addition, note that when burying with soil, the soil should be level, the clods fine, the covering firm, and the soil thickness uniform. In winter, check frequently, and if cracks are found, fill them again with soil.