Momordica charantia, commonly known as bitter melon, is a short-day plant that thrives in high temperatures and requires ample light. It is heat-tolerant, moisture-resistant, and can withstand limited shade. While it doesn’t have strict requirements for daylight duration, longer exposure to light promotes better growth. This crop needs higher soil moisture and air humidity but is not very tolerant of waterlogging. It has broad adaptability and can be grown in various soils across both northern and southern China. In recent years, many vegetable growers have started cultivating it in greenhouses or controlled environments to optimize yield and quality.
Choosing the right variety is crucial for achieving high yields. The white bitter gourd and green bitter gourd 915, developed by the Chinese Academy of Agricultural Sciences, are popular among farmers due to their excellent quality, high productivity, and strong disease resistance. Before sowing, seeds should be soaked in hot water at 55°C and stirred continuously. Once the temperature drops to 30°C, soak them for 12 hours (or 8 hours if the seeds are slightly opened). After washing, wrap the seeds in clean gauze and place them in a thermostat set at around 30°C. Rinse them daily with warm water, and germination usually begins within 4–5 days. This process helps eliminate pathogens and ensures healthy sprouting.
For open-field cultivation, seeds are typically sown in greenhouses first. A suitable seedbed mix is prepared the day before sowing, consisting of peat moss, vermiculite, and well-rotted manure in a ratio of 1:1:1:0.5, along with 1 kg/m³ of diammonium phosphate. After sieving and mixing, the soil is piled up, covered with plastic, and left for a few days. Before use, the soil is mixed evenly and placed into 10 cm x 10 cm planting pots or nursery trays. The planting area is marked in 10 cm x 10 cm squares, with small holes drilled 1 cm deep using a wooden stick. The next day, after watering the nutrient soil, a thin layer of fine soil is added, and the seeds are placed in the holes, ensuring the sprouts face downward. Cover the seeds with a 1.5 cm layer of soil and lightly sprinkle more fine soil on top. In Beijing, sowing typically occurs at the end of March or early April, with seedlings ready for transplanting about 30–35 days later, after the last frost in early May. Producing strong, healthy seedlings is essential for growing pollution-free vegetables.
After sowing, the greenhouse must be sealed to maintain warmth. Seedlings are placed under a small shed, covered with a plastic film to retain heat and moisture. The daytime temperature should be kept between 30–35°C, and the nighttime temperature around 15°C. When 50% of the seeds have emerged, the film should be removed promptly. Once the seedlings are fully out, the indoor temperature should be maintained at 20–25°C during the day and 10°C at night. Watering should be done sparingly, following the principle of temperature control rather than water restriction, to ensure robust growth. Gradually reduce the temperature in the shed and start ventilating a few days before transplanting to harden off the seedlings.
Bitter gourd is a thermophilic and heat-tolerant crop, so it requires sufficient base fertilizer. Apply 5,000 kg of high-quality organic manure and 30 kg of ammonium phosphate per 667 square meters. Mix thoroughly and form raised beds 1.5 meters wide. After a few days, dry the soil and create beds 80–90 cm wide and 10–15 cm high. Two days before planting, apply mulch. Plant in rows spaced 60 cm apart, digging shallow pits. Avoid digging too deep and cover the pits with soil after watering to prevent heat loss. After planting, install sturdy trellises. The distance between supports should be 20 cm (or 30 cm for thicker ones). Timely staking improves the microclimate and helps seedlings grow quickly. Plant approximately 1,300–1,600 plants per 667 square meters, using 250–300 grams of seeds.
After transplanting, water slowly and avoid overwatering, especially when the temperature is still low. A few days later, intensify cultivation to maintain soil temperature and promote plant growth. Due to its strong branching ability, select 2–3 thick vines from the lower part and tie them to the trellis, removing the rest. During this period, watering is generally not needed. When the first fruits begin to set and inflate, apply 10–15 kg of urea or 20–25 kg of ammonium bicarbonate per 667 square meters. Top-dressing should be adjusted based on weather, plant growth, and soil conditions—often referred to as "watching the sky, observing the land, and checking the crops." It's important to note that bitter gourd has a strong root system, and overwatering can lead to poor fruit development, weak growth, and increased risk of disease. Harvest commercial fruits about 40–50 days after transplanting, and remember to provide additional nutrients during the fruiting stage.
Diseases such as leaf mold and powdery mildew often occur in the late growth stages. To manage these, spray 50% thiophanate-methyl WP diluted 1,000 times or 10% triadimefon EC diluted 1,500 times. For aphid control, use 20% omethoate diluted 1,000 times. For red spider mites, apply Krypton at 1,500–2,000 times. Regular monitoring and timely intervention are key to maintaining healthy crops.
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