Recently, most areas of the district experienced low temperatures and freezing rain, with ice accumulation (glaze ice) persisting for several days in some high-altitude Tea gardens. Currently, in Yuhang District, only the earliest varieties such as Wuniuzao have begun to sprout, while other main varieties like Longjing 43, Yingshuang, and Jiukeng have not yet sprouted. The degree of damage varies among different tea varieties due to factors such as altitude and microclimate in the tea gardens.

Wuniuzao in Jingshan Town on February 25, 2024

Huanghu Town on February 26, 2024

Wuniuzao affected by frost (at an altitude of 300 meters)

The impact of this frost event mainly depends on its duration. After cold damage, symptoms may include broken branches, reddish-brown necrosis, and discoloration and drying of leaves to varying degrees. To minimize the effects of the cold damage and implement post-disaster remedial measures, the following technical guidance is provided.

.01 Timely Pruning

After frost damage, depending on the severity of the impact on the tea garden, different measures should be taken based on the principle of “catering to the majority and consistency within the same garden”:

1

For productive tea gardens:

1. If the branches and stems are not damaged (no reddish-brown necrosis appears): If buds have not sprouted, no pruning measures should be taken; if buds have sprouted and been affected, consider light pruning (taking into account the impact of delayed harvesting caused by pruning).

2. If the branches and stems are damaged (reddish-brown necrosis appears): Prune when the boundary between dead and healthy parts is clear. The cut should be 1-2 cm deeper than the necrotic part to stimulate the growth of axillary buds or adventitious buds below the cut.

2

For young tea gardens:

For severely frost-damaged young tea trees aged 1-2 years, if the mortality rate is not high, shape pruning can be performed, removing some dead branches and replanting where necessary; if a large area of young tea trees has been killed by frost, they need to be transplanted and regrouped for re-planting.

For tea gardens with ice accumulation, relevant measures should only be taken after the ice and snow have melted. Pruning should be carried out after stable temperature recovery and without a risk of spring cold, and should be done in a timely manner based on the degree of damage.

.02

Shallow Cultivation and Fertilization

After pruning frost-damaged tea plants, fertilization and water management must be strengthened to restore vitality and rebuild the canopy. Before the start of Spring Tea harvesting, perform shallow cultivation and weeding once to change the compacted surface soil layer, improve the air permeability and water drainage conditions of the soil, which helps loosen the soil, raise soil temperature, reduce the consumption of water and nutrients, and promote the sprouting of new buds. Shallow cultivation and weeding should be done around early March, to a depth of 5-10 cm. At the same time, in conjunction with garden cleaning, weeds and fallen leaves should be turned into the soil to reduce the number of pests.

After shallow cultivation, open trenches, apply sprout-inducing fertilizer, and cover with soil. The amount of fertilizer should be determined based on factors such as soil fertility, age of the tea plants, tea yield, and picking practices. Based on the average dry tea yield of Jingshan tea in Yuhang District, it is recommended to apply 10-20 kg of pure nitrogen from fast-acting nitrogen fertilizers (such as ammonium sulfate, urea, etc.) or high-nitrogen compound fertilizers per mu. Sprout-inducing fertilizer should be applied about 10-15 days before harvesting, usually by opening trenches around the roots of the tea plants. The soil should be covered back over the fertilizer promptly to prevent loss of effectiveness. For young tea gardens, the application of nitrogen fertilizer should be reduced according to the age of the trees, and phosphorus and potassium fertilizers should be applied appropriately.

.03

Preparation for Subsequent Spring Cold Events

According to meteorological forecasts, there is likely to be a late spring cold event around early March. Tea farmers must pay close attention and take preventive measures such as covering, activating anti-frost fans, and fumigating in advance.

1

Covering

For tea gardens on windward slopes that are prone to frost damage, use locally available materials like straw, weeds, non-woven fabric, or shade nets to cover the tea bushes when the temperature drops below 4°C. Remove the covers after the cold snap.

2

Activate Anti-Frost Fans

For tea gardens equipped with anti-freeze fans, inspect the equipment's operational status and set the operating temperature based on the microclimate of your tea garden to reduce the occurrence of frost.

3

Fumigating

Fumigating can prevent the radiation of heat from the ground, achieving insulation and frost prevention. For tea gardens where smoke disperses slowly and does not cause forest fires, fumigating can be used for frost prevention. Set up fumigation points at lower elevations in the tea garden (using bamboo powder as fuel), and conduct fumigating from 7 PM until 8 AM the next morning.

At the same time, we remind all tea farmers to stay updated with local weather information and regularly check the sprouting situation of different tea varieties in their gardens, predict the appropriate time for harvesting, and actively arrange for tea pickers. In addition, prepare in advance for Tea processing sites and equipment cleaning and disinfection, factory machinery configuration, machine maintenance, etc., to ensure smooth progress in spring tea production.

Contributed by: Agricultural Technology Extension Center