A Detailed Guide to Petunia Planting Methods and Technical Key Points

Under protected cultivation conditions in the middle and lower reaches of the Yangtze River, petunias can be sown and raised year-round. Since flowering is generally timed for May 1st and National Day, sowing times are: autumn sowing in October-November, spring sowing in June-July. Before sowing, fill the medium, water thoroughly, and after sowing mist finely to moisten the seeds. The seeds must not be covered with any medium, otherwise germination will be affected.

After sowing for seedling raising:After sowing, maintain the medium temperature at 22-24°C; seedlings emerge in 4-7 days. After the first pair of true leaves appears, apply a nitrogen fertilizer solution at a concentration of 50×10-6, and pay attention to ventilation; seedlings can gradually be exposed to light. When seedlings have 2-3 pairs of true leaves, the medium temperature can be lowered to 18-20°C, and every 7-10 days apply 0.1% urea solution or 0.1% compound fertilizer solution with an NPK ratio of 15-15-15.

Pay attention to ventilation:At this stage, ventilation should still be emphasized to prevent disease; spray with chlorothalonil or thiophanate-methyl at 800-1000 times dilution about once a week. When plants have 3 pairs of true leaves, the root system has formed well; temperature, humidity and fertilization requirements are the same as before, and attention should still be paid to ventilation and disease prevention.

Raise seedlings in 288-cell seedling trays; autumn-sown seedlings are transplanted directly into 13 cm diameter nutrient pots, while spring-sown ones are generally transplanted only into 10 cm diameter nutrient pots. They can also be planted first in a seedling bed and then moved into nutrient pots.

Light regulation:Petunias grown in summer are relatively tolerant of high temperatures; generally shading is only needed for a few days after transplanting to help them recover, and no shading is needed throughout the entire growth period.

Temperature control:After transplanting, petunias should be kept at around 20°C, not below 15°C; too low a temperature will delay flowering or even prevent flowering. In actual production, those required to flower for National Day must be grown in greenhouses to avoid low temperatures before National Day affecting flowering; those required to flower for May 1st can also be grown in the open field, but it must be ensured that winter frost does not fall directly on the leaves, otherwise white spots will appear on the leaves, affecting the ornamental effect. In the middle and lower reaches of the Yangtze River, protected cultivation facilities are generally used.

Watering should always follow the principle of not watering until dry, and watering thoroughly when you do. For potted flowers grown in summer, during the early growth stage of young seedlings, apply light fertilizer frequently; choose fertilizers with high nitrogen and potassium content and appropriately low phosphorus; for nitrogen fertilizer, urea can be chosen; for compound fertilizer, choose those with an NPK ratio of 15-15-15 or high in nitrogen and potassium, with concentration controlled at 0.1%-0.2%; for water-soluble fertilizers, generally choose 20-10-20 and 14-0-14, with concentration at 50×10-6-100×10-6.