The winter survival of Tea plants is a critical factor hindering the sustained development of our region's tea industry. Our area belongs to the sub-optimal tea-growing zone north of the Yangtze River, where tea plants must endure adverse conditions such as low winter temperatures. To ensure that tea plants are high-quality, efficient, and productive in an ecological manner, it is essential to manage their safe passage through winter.

Recent surveys have found that, due to relatively mild frost damage last year, some tea farmers may be complacent about winter protection measures this year. This could lead to untimely management, inadequate measures, and unscientific methods, especially regarding the construction of large, medium, and small arch-shaped greenhouses. As a result, tea plants may suffer from frost damage due to sudden changes in weather. Therefore, tea-producing villages, tea companies, tea cooperatives, and individual tea growers should enhance their awareness and take effective measures to implement winter protection for tea plants.

### 1. Biological Characteristics of Tea Plants

Four key features: “prefers acidity over alkalinity, light over direct sunlight, warmth over cold, and moisture over waterlogging.”

### 2. Causes of Frost Damage in Tea Plants

#### 1. Relation Between Frost Damage and Meteorological Factors

From a meteorological perspective, the causes of frost damage in tea plants are primarily low winter temperatures, drought, and strong winds. These factors often occur together, with low temperatures being the main cause. Drought and strong winds exacerbate the severity of frost damage.

#### 2. Relation Between Frost Damage and Variety and Age of the Plant

The severity of frost damage is also related to the age of the plant. Generally, as the plant ages, its resistance to cold increases gradually. For example, after an extreme minimum temperature of -13.5°C, a survey conducted 20 days later showed that the leaf damage rate was 63.3% for one-year-old tea plants, 50.3% for two-year-olds, 22.0% for three-year-olds, and only 19.0% for 13-year-old plants.

#### 3. Relation Between Frost Damage and Geographical Conditions

Frost damage in tea plants is closely linked to geographical conditions. Tea plants grown at high latitudes and altitudes are more susceptible to freezing. In certain areas, even though tea plants can grow normally, they require special protective measures to survive the winter safely.

Different terrains and orientations are also significant factors affecting whether or not frost damage occurs. In general, high Mountain tea gardens are more prone to frost than those on hills or plains. Cold air tends to accumulate in specific areas of mountain tea gardens, leading to more severe frost damage. Additionally, areas between mountains exposed to “return winds” in winter are also more prone to frost damage.

#### 4. Relation Between Frost Damage and Garden Management

Proper use of various garden management techniques can enhance the plant's resistance to cold, ensuring safe winter survival or reducing the severity of frost damage. Conversely, poor long-term management can result in severe frost damage. Factors such as improper fertilization, excessive picking, severe pest infestations, poor ecological conditions in the garden, and inadequate winter protection measures all directly affect the plant's ability to survive the winter safely. Routine management based on the plant's habits and environmental conditions is necessary to ensure safe winter survival.

### 3. Comprehensive Winter Protection Measures for Tea Plants

#### (a) Cultivation Measures

1. **Apply Base Fertilizer Early and Amplely**
– Tea plants have a deep root system and are naturally drawn to nutrients. Therefore, winter fertilization should involve digging trenches for deep application, followed by covering the soil to prevent nutrient loss.
– **Note:** For one- to two-year-old tea plants, dig a trench approximately 15 cm wide and 15-20 cm deep, parallel to the row of tea plants, 10-15 cm away from the base of the trunk. For three- to four-year-old plants, dig a trench 20-25 cm deep, 35-40 cm away from the base. For mature tea gardens, dig a trench outside the canopy, 20-30 cm deep. Fertilizing should be completed by late October.

2. **Ensure Adequate Winter Watering**
– In our region, the saying goes, “Adequate winter watering can withstand seven-tenths of disasters.” Adequate winter watering significantly enhances the plant's resistance to freezing and improves photosynthesis. In northern tea regions, where winters are dry, widespread winter watering is crucial.
– **Note:** Watering too early does not achieve the desired anti-freezing effect, while watering too late can have counterproductive effects due to frozen ground. It is best to water about ten days before the ground freezes. In case of drought during early winter, water early. Generally, avoid watering after the ground has frozen.

3. **Tea Garden Pruning**
– After closing the garden, lightly prune or top mature tea gardens, leaving enough green leaves to enhance winter survival. Remove hanging branches, branches near the ground, diseased and insect-infested branches, and weak branches using a single-sided pruning machine. Prune diagonally towards the inside of the tea plant to improve ventilation and reduce nutrient consumption and the number of overwintering pests.
– **Note:** For tea gardens prone to frost damage, prune to remove tender shoots that cannot survive the winter, as this will affect the emergence of spring buds. Young tea plants should focus on nurturing, shaping, and developing the canopy.

#### (b) Pest and Disease Control

1. **Comprehensive Garden Cleanup**
– The primary pests and diseases overwintering in our region's tea plants include the tea green leafhopper, green stink bug, and anthracnose. Winter garden cleanup can eliminate overwintering pests and reduce the incidence of pests and diseases in the following year.
– **Note:** Weeds and dead branches and leaves provide habitats for these pests and diseases. Combine pruning with the removal of weeds around the garden, dead branches and leaves at the base of the tea plants, and pruned branches and diseased leaves. This helps to reduce the number of overwintering pests in the garden.

2. **Garden Closure**
– The quality of garden closure directly affects the number of pests and diseases in the following year. Typically, apply 50 kg per mu of 45% crystal sulfur suspension agent diluted 100-120 times to seal the garden. Ensure thorough spraying of the branches, leaves, and both sides of the leaves. Also, spray weeds along the garden embankments and protective trees comprehensively to reduce the number of overwintering pests.
– **Note:** Do not mix sulfur suspension agent with other pesticides. Apply it as soon as possible under suitable temperature conditions. The optimal temperature range for applying sulfur suspension agent is 5-20°C. Do not use it in tea gardens when the temperature is above 20°C or below 5°C.

#### (c) Freeze Prevention

1. **Covering the Garden with Straw (or Film)**
– Before the ground freezes, cover the rows of tea plants with straw. Materials suitable for covering include peanut shells, rice straw, wheat chaff, or wheat straw. The thickness of the straw layer should be around 10 cm, which can increase soil temperature by 1-4°C, reduce the depth of frozen soil by approximately 15 cm, and increase soil moisture content by around 5.7%.
– **Note:** Covering with straw is most appropriate around the time of “Start of Winter.” Covering after the ground has frozen can have the opposite effect.

2. **Covering the Canopy with Straw (or Shade Net)**
– Materials can include fresh pine branches, rice straw, corn stalks, etc. If conditions permit, add a layer of used greenhouse film, shade net (with 40% light transmission), or plastic woven cloth. Covering the canopy with straw protects against frost and cold winds, reduces water evaporation, and narrows the temperature difference between day and night.
– **Note:** Cover the canopy around the time of “Light Snow,” leaving 30-40% of the canopy exposed to direct sunlight (sparse exposure).

3. **Windbreaks**
– The best material for windbreaks is straw mats, which can be reused for 2-3 years. Alternatively, plastic film can be used to construct windbreaks. Construct windbreaks around the time of “Light Snow,” placing the mats or film on the north side of each row of tea plants. Secure the base with soil, ensuring the mats are 20 cm higher than the canopy and tilted forward at 60° to allow light to pass through the front and protect the back.
– **Note:** Windbreaks should be constructed on the north and west sides of the garden, facing the wind.

4. **Facility Protection**
– Based on the terrain, elevation, age of the tea plants, and size of the canopy, choose small, medium, or large arch-shaped greenhouses or warm-season greenhouses for protection. Use materials such as galvanized pipes, bamboo strips, cold-drawn steel bars, and concrete posts for the frame. Choose agricultural film with low light transmission for the cover. If conditions permit, perform shading treatment. Ensure the film is 10 cm away from the upper and lateral branches of the tea plants to avoid scorching the leaves.