The U.S. Black Lee, also known as the American Black Plum, is referred to by various names in different regions, such as Black Rose Plums, Black Amber Plums, Black Browns, Black Libes, and Beautiful Plums. The variety was originally introduced from the United States, and it gets its name from the striking deep purple-black color of the fruit. This unique appearance has made it a popular choice among growers and consumers alike.
This variety is highly adaptable, grows quickly, produces fruit early, and yields significantly. When planted in March of the first year, it 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 typically weighs between 80 to 120 grams. The skin is dark purple-black, while the flesh is yellow, juicy, and sweet, with a sugar content exceeding 13 degrees. Its high quality, with an edible rate over 95%, makes it very appealing. In regions like Yuebei, Guangdong, the fruit ripens from late May to early June, and the market price in Guangzhou remains stable at 8 yuan per kilogram or higher, making it a promising and profitable fruit variety with broad market potential.
Below are the key points for suitable growing conditions and main cultivation techniques:
**1. Suitable Planting Areas:**
The U.S. Black Lee 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 reduce fruit production. According to field studies, this variety performs best in areas where winter frosts occur. In regions without frost, the yield tends to be lower or the results are less significant.
**2. Main Cultivation Techniques:**
1. **Land Selection:** The plum tree is adaptable and can be grown on both slopes and flat land. For optimal growth, choose deep, well-drained soil that receives plenty of sunlight.
2. **Planting Spacing:** It's recommended to plant them at 4x3 meters or 3.5x3.5 meters, which allows for about 60 trees per acre.
3. **Planting Time:** Spring and autumn are both suitable planting times. Autumn planting is usually done between November and December, while spring planting is also effective.
4. **Planting Requirements:**
- Dig pits and apply base fertilizer before planting.
- Ensure at least 10% of pollination trees within the orchard. 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:**
- Young trees should be fertilized with nitrogen-rich materials before the spring and summer shoots emerge. Urea or well-decomposed manure can help promote healthy growth.
- For mature trees, apply flowering fertilizer 10 days before budding, then a strong fruit fertilizer during the rapid fruit expansion phase. These two stages should use a mix of nitrogen, phosphorus, and potassium.
- After fruit harvest, apply organic fertilizers like peanut bran and chicken manure, along with a small amount of urea.
- In winter, combine deep tilling with the application of various organic fertilizers to improve soil quality.
**B. Shaping and Pruning:**
- **Juvenile Trees:** Shape the tree into a natural open center. Cut back the main stem to 60-80 cm after planting, and select 3-4 branches as the main ones. Shorten the main branches when they reach 50-60 cm, always cutting outward.
- **Fruit-bearing Trees:** 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. Long and medium-length fruiting branches should be pruned by about one-third and one-half respectively. Avoid cutting short fruiting branches and bouquet-shaped branches unless they are too dense. Remove dead, diseased, or damaged branches to improve light exposure and reduce disease spread.
**C. Pest Control:**
- Common diseases include gummosis, anthracnose, and black spot. Prevent gummosis by avoiding wounds and using antiseptic treatments like carbendazim or thiophanate-methyl.
- Insect pests include aphids, scale insects, and red-necked beetles. Control measures include clearing the garden in winter, burning infested branches, and applying insecticides like trichlorfon or imidacloprid during leaf development and flowering periods.
With proper care and management, the U.S. Black Lee can thrive and provide a rewarding harvest, making it a valuable addition to any orchard.
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