Not only was February 22, 2022 a Tuesday, but it was also the 22nd day of the first month in the Year of the Tiger. On this day filled with love, everything around us was covered in white. Has your social media been flooded with snow pictures?
(Leishan Tea garden, photo by Wu Xianhai)
According to the provincial meteorological bureau, from 08:00 on February 21 to 08:00 on February 22, 2022, light snow or sleet occurred in 77 counties (cities and districts) across the province, with snow accumulation observed in 72 county districts, the deepest being 12 cm in Wanshan. Ice build-up on power lines was recorded in 25 stations, with the largest diameter being 32 mm in Wanshan (including the conductor diameter of 26.8 mm). The lowest temperature in 76 counties (cities and districts) was 0°C or below, with Weining recording the lowest at -6.3°C. Road icing persisted in most areas except for the southern borders of the province.
As the saying goes, “A timely snow promises a good harvest.”
But what impact do this year's frequent rainy and cold weather conditions have on tea gardens that are about to enter their main picking season?
(Kaiyang tea garden, photo by Zhang Chun)
It is known that low-temperature hazards in tea gardens include cold injury and Frost damage.
Cold injury (or chilling injury) refers to the damage caused to tea plants when they encounter abnormal low temperatures during their growth cycle, typically above 0°C, such as spring cold waves or autumn cold snaps, which can delay bud break and slow down growth.
Frost damage occurs when the air or soil temperature drops below 0°C for a short period, causing ice formation within the plant, leading to frost damage and even death. In mild cases, there may be slight damage and discoloration to the edges of young leaves and buds, with little effect on the branches. More severe cases result in frozen branches and discolored mature leaves, darkened and brown axillary buds. In more serious cases, some branches dry out. Severe frost damage can cause the main branches and Tree Bark to crack, the outer layer to separate from the branch, and even longitudinal splitting and death of the main branches and the entire tree.
The types of frost damage in tea plants include:
1. Root frost damage: After root frost damage, the outer cortex turns brown, separates from the woody part, and may even peel off. Above-ground parts show delayed bud break in spring or uneven emergence. In milder cases, although new shoots can emerge, growth is slow. In severe cases, new shoots gradually wilt and dry out.
2. Trunk frost damage: This primarily manifests as basal trunk frost damage, trunk splitting, and branch freezing. Basal trunk frost damage is common in young tea plants, where frost damage occurs 8–10 cm above ground level. In mild cases, only the sunny side of the trunk's cortex and cambium layer split longitudinally and turn brown and die. In severe cases, the shady side also dies, forming a dead ring around the trunk, causing the whole plant to die.
3. Tender branch frost damage: Late-developing, immature tender branches have lower frost resistance and are prone to Drying out and dying after frost damage.
4. New bud frost damage: If late frosts occur, mild cases can cause the tips of buds and leaves to turn red. Severe cases can cause entire patches of buds and leaves to wither and become scorched, creating a “pockmarked” appearance, severely affecting both yield and quality.
(Meitan tea garden, photo by Liu Fengying)
What should we do before the disaster strikes?
1. Insulate and warm up the nursery: Securely cover and press down the shade nets and films to prevent the nursery from freezing. During rain and snow, promptly check and clear the accumulated snow on the canopy, and repair any damaged nursery frames. Pay attention to water management in the nursery to prevent the tea seedlings from becoming dehydrated due to frozen soil lifting them. Timely drain the water from the nursery to prevent damage to the roots of the tea seedlings from the melting snow and ice.
2. Protect young tea gardens from frost: Use measures like covering the tea seedlings with straw and applying additional soil to prevent them from freezing. After the temperature warms up, promptly check the frost-damaged tea gardens and take corrective actions like manually clearing snow, pruning branches, and replanting robust seedlings. The depth of pruning varies depending on the severity of the freeze, aiming to cut 1–2 cm deeper than the frozen area.
3. Protect production tea gardens from frost and reduce damage: For production tea gardens, use measures such as laying straw between rows, covering the canopy with non-woven fabric or shade nets, and using sprinkler systems and frost fans if facilities are available. Promptly drain water from the tea gardens.
How do we remedy the situation after the disaster?
Closely monitor the extent of frost damage in production tea gardens. When normal temperatures return, prune and strengthen fertilizer and water management to restore the vigor of the trees. For severely damaged old tea gardens where remedial measures are difficult, replant with frost-resistant clonal varieties, remove the damaged plants, and enhance fertilizer and water management to ensure the survival rate and growth of the transplanted seedlings.
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