The U.S. black plum, also known as the American Black Plum, is referred to by various names across different regions, such as Black Rose Plum, Black Amber Plum, Black Brown Plum, Black Libe Plum, and Beautiful Plum. This variety was originally introduced from the United States, and its fruit has a striking purple-black color, which is why it's commonly called "American Black Plum."
This variety exhibits strong adaptability, fast growth, early fruiting, and high yields. Trees planted in March of the first year can bear 2-3 kilograms of fruit in the second year, and by the third year, the yield can exceed 20 kilograms per tree. Each fruit weighs between 80 to 120 grams, with a deep purple-black skin, yellow flesh, and a sweet, juicy flavor. The sugar content exceeds 13 degrees, making it a high-quality fruit with an edible rate of over 95%. In regions like Yuebei and Guangdong, the fruit ripens from late May to early June. Due to its stable market price—often above 8 yuan per kilogram in Guangzhou—it presents a promising opportunity for commercial fruit cultivation.
Below are the key points regarding suitable growing conditions and main cultivation techniques:
**1. Suitable Growing Areas:**
The American Black Plum is heat-tolerant but not cold-resistant. It can survive winter temperatures as low as -28.3°C without frost damage. However, excessive heat during winter may lead to poor results. According to surveys, this variety performs best in areas with mild winters. In regions where there is no significant cold, the fruiting performance may be weak or yields may be low.
**2. Main Cultivation Techniques:**
1. **Land Selection:** The tree adapts well to both sloped and flat land. It is best to choose deep, well-drained soil that receives ample sunlight.
2. **Planting Spacing:** It is recommended to plant at intervals of 4x3 meters or 3.5x3.5 meters, which allows for approximately 60 trees per acre.
3. **Planting Time:** Spring and autumn are both suitable planting seasons. Autumn planting is typically done from November to December, while spring planting is also an option.
4. **Planting Requirements:**
- Dig planting pits and apply base fertilizer.
- Ensure that at least 10% of the orchard includes pollination trees. American Red Plums are recommended as pollinators, as most plum varieties are self-incompatible and require cross-pollination to increase yield.
5. **Field Management:**
**(A) Fertilization:**
- For young trees, nitrogen-based fertilizers are used to promote shoot growth. Apply urea or decomposed manure before the spring and summer shoots emerge.
- For fruit-bearing trees, apply flowering fertilizer 10 days before bud break, followed by a strong fruit fertilizer during the rapid fruit expansion phase. Use a balanced mix of nitrogen, phosphorus, and potassium.
- After fruit harvest, apply organic fertilizers such as peanut bran and chicken manure, along with a small amount of urea.
- In winter, combine deep plowing with the application of organic compost to improve soil quality.
**(B) Pruning and Shaping:**
- **Juvenile Tree Shaping:** The natural happy shape is commonly used. Cut back the main stem to 60–80 cm after planting, and select 3–4 branches from the current year’s growth as the main branches. When these branches reach 50–60 cm, they should be pruned, cutting outward to encourage a balanced structure.
- **Fruiting Tree Pruning:** Focus on shortening fruiting branches and managing the main branches. Aim to form short fruiting branches and bouquet-like clusters. Adjust pruning based on the tree's age and vigor. Trim long and medium fruiting branches by about one-third and one-half respectively. Avoid cutting short fruiting branches or bouquet-shaped branches unless they are too dense. Remove dead, diseased, or damaged branches to improve air circulation and reduce disease spread.
**(C) Pest and Disease Control:**
- Common diseases include gummosis, anthracnose, and black spot. Prevention involves maintaining tree health, avoiding mechanical injuries, and whitewashing trunks in winter. Treatments may include antiseptic agents like carbendazim and thiophanate-methyl.
- Major pests include aphids, scale insects, and red-necked beetles. Control measures include clearing the garden in winter, burning infested branches, and using insecticides like trichlorfon and imidacloprid during leaf development and flowering periods. Regular monitoring and timely intervention are essential for effective pest management.
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