How to prevent and control freeze damage in tea plants? Taking active measures is key

Freeze damage is a major weather-related disaster affecting tea plants. After tea plants suffer freeze damage, it can range from affecting tea yield and quality in mild cases to causing severe leaf drop or even the death of the entire plant in severe cases. Freeze damage to tea plants can be divided by growth season into overwintering-period freeze damage and sprouting-period freeze damage, with the latter having the greatest impact on the yield and quality of that year's spring tea.

Prevention of overwintering-period freeze damage

During the growing season, strengthen fertilizer and cultivation management, pay attention to pest and disease prevention, implement a combination of harvesting and nurturing, and promote vigorous growth of tea plants so as to accumulate more organic matter and improve resistance to low temperatures. In autumn and winter, apply heavy base fertilizer, especially organic fertilizer, to help raise soil temperature.

During intervals between tea farming tasks, carry raw soil from the surrounding barren hills and spread it in the tea garden, and rake the soil around the tea plant roots level, promoting the tea plants to root downward. This helps retain fertilizer, water, and heat, both promoting tea plant growth and enhancing cold resistance.

The timing of leaf retention in high-mountain tea gardens is closely related to freeze damage in tea plants. Retaining leaves in the late autumn tea period makes the leaves tender and soft during winter, making them prone to freeze damage. The leaf retention period should be at the end of spring tea or the beginning of summer tea; at this time the leaves have already matured by winter, have strong resistance to low temperatures, and help the tea plants overwinter safely.

Spreading grass between rows in tea gardens can both resist drought and prevent freezing. In grass-covered tea gardens, winter low temperatures can be increased by 1-2°C compared with tea gardens without grass cover, which can reduce the degree and depth of frozen soil and maintain soil moisture.

In autumn, interplant overwintering green manure between tea garden rows to cover the ground, which can raise soil temperature and help reduce freeze damage; in spring these green manures can also serve as fertilizer. Suitable green manures for interplanting include peas, vetch, alfalfa, and others.

Establishing shelterbelts in tea gardens can reduce wind speed within the area, regulate temperature, reduce evaporation, and noticeably improve the microclimate of the tea garden. Planting shelterbelt strips at windward openings in high-mountain tea gardens can effectively resist cold wave attacks.

Prevention of late frost damage

Late frost damage has a major impact on the production of famous and high-quality tea, so actively preventing late frost damage is very important. In addition to adopting the prevention measures for overwintering-period freeze damage, the following measures can also be taken to prevent late frost damage:

Smoke fumigation to drive away frost. The role of smoke fumigation is to form smoke in the tea garden air, prevent the radiative diffusion of heat, and use the "greenhouse effect" to prevent late frost damage, with obvious results. The method is that before late frost damage arrives, set up piles according to wind direction, terrain, and area, and ignite when the temperature drops to about 2°C, both preventing late frost damage and accumulating fertilizer, achieving two goals at once.

Spray water to wash off frost. Tea gardens with water sources and sprinkler irrigation equipment can use this equipment to spray water when late frost damage occurs, washing away the frost covering the tea buds and leaves.

Covering to prevent frost. Before low-temperature cold waves arrive, cover the canopy with rice straw, weeds, shade nets, and the like to protect the tea plants and resist frost damage.

Methods used abroad to prevent late frost damage in tea gardens also include the air-blowing method (installing fans in the field), the water-spraying ice-forming method (maintaining bud and leaf temperature at about 0°C), and the heating method (raising the temperature of the tea plant canopy), among others.

Remedial measures after freeze damage

Pruning and trimming. For tea plants that have suffered severe freeze damage (branches and leaves frozen to death or withered by freezing), after the temperature warms up, immediately prune the frozen branches and leaves to prevent frozen buds and leaves from sprouting. The pruning height should be controlled to cut away the frozen-dead branches and leaves, with light pruning for slight freeze damage. Pruning too heavily will further delay the sprouting and growth of spring shoots, delay the picking time, and affect yield, while pruning too shallowly or too lightly will have poor results. However, for tea gardens with no freeze damage symptoms on the canopy surface, pruning may not be carried out before spring tea, and the light pruning period can be changed to mid-May after spring tea. This can advance the sprouting of spring tea and allow early picking of famous and high-quality tea.

Shallow tillage and fertilization. Freeze damage causes some trauma to tea plants, so shallow tillage and fertilization should be carried out as early as possible. After overwintering-period freeze damage occurs, apply heavy spring bud-promoting fertilizer, with the fertilization amount increased by about 20% over the original, while also applying a certain amount of phosphorus and potassium fertilizer. After sprouting-period freeze damage occurs in tea plants, when the spring buds are at the fish-leaf stage to the 1-leaf unfolding stage, spray foliar fertilizer, which promotes the recovery of tea plant vitality and the sprouting of tea buds and growth of new shoots.

Cultivating the canopy. For tea plants that have been lightly pruned after suffering freeze damage, leave 1 large leaf when picking spring tea, and pick summer and autumn tea according to conventional methods. This both helps cultivate a good canopy and allows picking some high-grade quality tea, reducing losses caused by freeze damage. For frozen tea plants that have undergone heavy pruning or collar pruning, priority should be given to nurturing, with specific requirements referring to the cultivation and management of heavily pruned and collar-pruned tea gardens.

Clearing ditches and draining water. For tea garden plots with poor drainage and waterlogging, promptly take advantage of sunny days to clear ditches and drain water, so that the groundwater level is lowered below the tillage layer.