Petunia cultivation and management techniques
Petunias can be sown throughout the year in protected areas, particularly in the middle and lower reaches of the Yangtze River. To ensure flowering around May 1st and National Day, sowing is typically done in October to November for autumn planting and June to July for spring planting. Before sowing, prepare the growing medium and water it thoroughly. Since petunia seeds are very small, they should be sown as wet seeds without covering them with soil, as this can hinder germination. Maintain a temperature of 22-24°C after sowing, and seedlings should emerge within 4-7 days. Once the first pair of true leaves appears, apply a diluted nitrogen fertilizer (5010-6) solution, while ensuring good ventilation and gradual exposure to light. When the seedlings have 2-3 pairs of true leaves, reduce the temperature to 18-20°C and apply either 0.1% urea or 0.1% 15-15-15 NPK fertilizer every 7-10 days. Continue to ventilate and monitor for disease; spraying chlorothalonil or thiophanate-methyl at 800-1000 times dilution every other week is recommended.
Transplanting is usually done when seedlings have developed 288 points. For autumn sowing, directly transfer them into 13 cm diameter pots, while spring sowing often uses 10 cm diameter pots. Seedlings can also be raised on a seedbed before being moved into the pots.
Lighting requirements vary depending on the season. During summer, petunias need partial shade for a few days after transplanting to help them acclimate. They do not require full shade during the rest of their growth period.
Temperature control is essential. After transplanting, keep the temperature around 20°C, not below 15°C. If temperatures drop too low, flowering may be delayed or prevented. For National Day blooms, greenhouse production is ideal to avoid early blooming due to cold weather. For May 1st blooms, open field cultivation is possible, but frost protection is necessary to prevent leaf damage. In the middle and lower reaches of the Yangtze River, most growers use protective structures.
In terms of cultivation and management, watering should follow the principle of "not overwatering." For summer potted plants, apply a diluted fertilizer with high nitrogen and potassium, low phosphorus, such as urea or 15-15-15 compound fertilizer. The concentration should be between 0.1%-0.2%, using water-soluble fertilizers like 20-10-20 or 14-0-14 at 5010-6 to 10010-6. Winter potted plants are usually produced from March to April, with top-dressing applied based on plant growth. Petunias are generally not pruned, but in summer, pruning may be necessary. If plants aren’t sold immediately, a single pruning can be done, followed by repotting, regular feeding, and proper care, which won’t affect the quality.
Pest and disease control is crucial. Common diseases include damping-off in the seedling stage (controlled with chlorothalonil or thiophanate-methyl at 800-1000 times), and stem rot during the growing season. Common pests include diamondback moth, aphids, and leafrollers, especially in National Day flower production. Avoid using cypermethrin on aphids, as it can cause phytotoxicity and harm plant growth.
For garden quality, winter potted flowers are typically grown in 12 cm diameter pots, with a crown height of 20-25 cm, resulting in a neat, full bloom. Summer potted flowers use 10 cm pots, with a crown of 15-18 cm. Petunias are suitable for long-distance transport and maintain good quality even after transit.
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