Tea plant frost damage refers to the freezing injury that occurs when tea plants are exposed to temperatures below 0°C during the winter dormancy period. The parts of the tea plant most susceptible to frost damage are often the current year's shoots, flower buds, young fruits, and root necks. When a young shoot is slightly damaged by frost, only the pith of the branch may change color. With moderate frost damage, the xylem changes color, and severe frost damage can result in damage to the phloem. When the cambium layer changes color, the branch loses its ability to recover. Damage to the root neck can lead to weakened or complete death of the tea plant.
1. How is tea plant frost damage classified? What are the main symptoms?
Frost damage can be categorized based on the cause into snow frost, wind frost, and frost.
(1) Snow Frost. Snow damage is a common form of frost damage to tea plants, particularly in high-latitude and high-altitude tea gardens. Tea plants suffering from snow damage show branches broken under the weight of accumulated snow, as well as freezing injury due to alternating freeze-thaw cycles during melting periods, causing uneven temperature changes. In severe cases, this can lead to withering and leaf loss. Continuous sub-zero temperatures with unthawed snow accumulation and increasing depth can cause prolonged snow pressure, leading to leaf loss, broken branches, and lodging. During the melting process, if the temperature drops again, it can cause the Tree body and soil to freeze, resulting in cell death in the root system and shoots and buds. Initially, leaves turn reddish-brown before Drying up and falling off, and in severe cases, the main branches die.
(2) Wind Frost. In the severe winter, cold air passages and low-lying areas where cold air accumulates, accompanied by dry and cold northwest winds and “return winds,” can cause the tea plant leaves to be blown off. Excessive evaporation within the tea plant leads to red and scorched buds and leaves, which curl and then fall off, while the branches become dry and cracked. In severe cases, productive branches and main branches die.
(3) Frost. Depending on the time of occurrence, frost can be divided into early frost and late frost. Early frost typically occurs at the end of autumn, while late frost generally appears in March-April. Late frost (often referred to as “spring cold snap”) has the greatest impact on premium teas, as it occurs when the earth warms up, and tea buds begin to sprout. Some early varieties may even reach the harvest season. If affected by late frost, minor damage can cause the tips of the buds and leaves to turn red, while severe damage can cause entire batches of buds and leaves to wither, significantly affecting the yield and quality of premium teas.
2. What are the main protective measures against frost damage in tea gardens?
(1) Scientifically Select Garden Locations. When developing new tea gardens in mountainous areas, prioritize sunny slopes sheltered from the wind and avoid cold air passages and low-lying areas prone to accumulation. This prevents “return winds” and “gully winds” from causing frost damage to the tea plants.
(2) Choose Frost-Resistant Tea Plant Varieties. Frost resistance in tea plants is determined by genetic factors and long-term natural selection, forming biological characteristics. Enhancing the tea plant's innate ability to withstand low temperatures is the fundamental approach to preventing frost damage.
(3) Mulching Between Rows in the Tea Garden. Suitable materials include rice straw, crop stalks, turf, leaves, sawdust, manure, and rice/wheat hulls. Mulching in the tea garden helps retain soil moisture and improve the organic content of the garden soil, promoting soil aggregation and enhancing soil resilience. Applying mulch before the soil freezes in winter can increase ground temperature by 1-2°C, reduce the depth of frozen soil, and maintain soil moisture. When applying mulch, place thicker layers closer to the roots of the tea plants, and around 10 centimeters between rows.
(4) Covering the Canopy of Tea Plants. In high-altitude tea gardens facing northwest, which are vulnerable to cold winds or snow and ice, covering the canopy with rice straw, miscellaneous grass, or plastic film can be effective. Covering the canopy can prevent direct exposure to dry cold winds and mitigate the harm caused by snow and ice thawing. In spring, remove the coverings appropriately and use them locally for composting.
(5) Timely Deep Plowing and Appropriate Fertilization. Timely deep plowing and drainage can promote the extension of fine roots into deeper soil layers, enhancing frost resistance. While deep plowing, mound 5-10 centimeters of soil around the root neck of the tea plants (for bush planting) or along both sides (for row planting). The internal nutrients of the tea plant serve as the material basis for successful overwintering. Fertilization can increase the content of Glucose, sucrose, and starch in the leaves or branches of the tea plant, thereby improving its frost resistance. Typically, fertilization is combined with deep plowing, usually carried out in late October to early November.
(6) Installing Blowers. Blower frost protection involves installing blowers 6.5 meters above the ground. When the blowers run, they alter the structure of cold air settling above the tea garden, blowing warm air from the inversion layer down to the tea picking surface, thus raising the surrounding temperature of the tea plants and achieving frost prevention.
3. What are the remedial measures after tea plant frost damage?
After a tea plant experiences frost damage, if effective rescue measures are not promptly taken, there will be a noticeable reduction in yield. However, if specific measures are implemented according to the degree of frost damage in different tea gardens, severely damaged tea plants can recover their vigor, and those with less severe damage can achieve stable yields.
(1) Pruning Frozen Branches and Leaves. After frost damage, some branches and leaves lose their vitality and must be pruned to encourage new shoots, cultivate the canopy, and expand the picking surface. The depth of pruning should be determined based on the severity of the frost damage, with the cut made about 1-2 centimeters deeper than the dead part to prevent further downward dieback. For tea plants where only the edges of the leaves have changed color and the frost damage is relatively mild, pruning is unnecessary. Pruning should be performed after local spring temperatures stabilize and rise.
(2) Strengthening Fertilizer and Water Management. After pruning frost-damaged tea plants, fertilizer and water management should be strengthened to help the tea plants quickly regain their vitality and rebuild the canopy. After temperatures rise and pruning is performed, apply quick-release fertilizers such as ammonium sulfate and urea, along with a certain amount of phosphorus and potassium fertilizers. Fertilization should be done in small amounts and multiple times. The timing of fertilization should vary based on the extent of pruning.
(3) Cultivating an Effective Canopy. After pruning, frost-damaged tea plants should be allowed to grow to restore the canopy. For lightly pruned tea plants, pick high-quality teas early in the spring season and later leave more leaves on the plant. For heavily pruned tea plants, leave one leaf during the spring tea harvest and also leave more leaves during the summer harvest. For severely pruned tea plants, where the plant height is less than 50 centimeters, appropriate top-pruning is recommended. For plants reaching 50 centimeters in height, two leaves should be left during the spring harvest and one leaf during the summer harvest to quickly restore the canopy. For tea plants that have undergone stump cutting, focus on nurturing the summer and autumn teas, picking the higher parts while allowing the lower parts to grow, inhibiting the growth of the main branches, and increasing branching density. In the second year, combine harvesting with pruning. When the plant width reaches 50-70 centimeters, it can enter full-scale production, combining harvesting with light pruning to shape the tree and develop the picking surface.
(4) Promptly Clearing Accumulated Snow. After heavy snowfall, when the snow layer has not yet frozen, organize personnel to promptly clear the snow from the canopy to prevent the tea plants from being damaged by the weight of thick snow. This also prevents the tea plants from freezing due to sudden temperature drops during the melting process.
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