How to grow petunias? A detailed guide to the latest cultivation methods
The petunia is actually not the morning glory; its scientific name is Petunia hybrida, a perennial herbaceous plant of the genus Petunia in the Solanaceae family, also known as shuttlecock flower, dwarf trumpet, sweet potato flower, etc. It originated in Argentina, South America, and is now widely cultivated around the world. It is commonly grown for ornamental display in city parks across northern and southern China. In a suitable climate or under greenhouse cultivation it can bloom in all four seasons. Let us take a look together at the scientific name and the cultivation methods of the petunia!
Growth habits of the petunia
The petunia likes a warm environment with plenty of sunlight. It is not tolerant of frost and is afraid of waterlogging. The optimum growing temperature is 13-18°C; in winter the temperature should be 4-10°C. If it falls below 4°C, the plant stops growing. In summer it can withstand high temperatures above 35°C. During the high-temperature summer season, water in the early morning and evening to keep the potting soil moist. In the plum rain season there is a lot of rain, which is very unfavorable for the growth of petunias; when the potting soil is too wet, the stems and leaves tend to grow leggy, and when there is a lot of rain during the flowering period, the flowers easily fade or rot. If the potting soil is waterlogged for a long time, the roots will rot and the plant will die. Therefore, potted petunias should be grown in loose, fertile sandy loam with good drainage. The petunia is a long-day plant and requires plenty of sunlight during the growing period. Under normal light conditions, it takes about 100 days or so from sowing to flowering.
Propagation of petunias by sowing
In the middle and lower reaches of the Yangtze River, under protected conditions, petunias can be sown and raised as seedlings all year round. Since the flowering period is generally controlled for May 1 and National Day, the sowing time is October-November for autumn sowing and June-July for spring sowing. Before sowing, fill the medium, water it 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, keep 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; the seedlings can also gradually be exposed to light. When the seedlings have 2-3 pairs of true leaves, the medium temperature can be lowered to 18-20°C, and every 7-10 days apply a 0.1% urea solution or a 0.1% compound fertilizer solution of nitrogen-phosphorus-potassium 15-15-15. At this stage, ventilation should still be noted to prevent disease, and about every 1 week spray with chlorothalonil or thiophanate-methyl at 800-1000 times dilution. When the plant has 3 pairs of true leaves, the root system has already formed well. The temperature, humidity and fertilization requirements are the same as before, and ventilation and disease prevention should still be noted.
How to grow petunias?
1. Fertilization: Petunias like fertilizer, and the difference between using and not using fertilizer is huge. After 4 true leaves appear and up to the temporary planting stage, apply Biwang at 2000 times dilution once a week. From temporary planting to final planting, apply Biwang at 1500 times dilution once a week. During temporary planting, a little slow-release fertilizer can be added appropriately. From final planting to the stage when the plant is full, apply Biwang at 1000 to 1500 times dilution twice a week. From the bud stage to the full bloom stage, apply Biwang and Bikaihua at 1000 times dilution mixed together twice a week. Sometimes petunias lack iron, so a little ferrous sulfate can be added.
2. Watering: Petunias like dryness and fear moisture. During growth they need sufficient water, especially in the high-temperature summer season, when they need a lot of water. You can water in the early morning, at noon and in the evening to keep the potting soil moist, but do not cause waterlogging in the pot; otherwise, long-term waterlogging in the pot will cause root rot and lead to the death of the plant. Do not let it be too wet either, otherwise the stems and leaves easily grow leggy.
3. Light: The petunia is a long-day plant and requires plenty of sunlight during the growing period. Under normal light, most petunia varieties take about 70-90 days from sowing to flowering. If there is insufficient light or too many cloudy and rainy days, the plant's flowering will often be delayed by 10-15 days, and there will be fewer flowers. If the plant grows in a long-day environment in spring and summer, it will quickly form buds, and the time from sowing to flowering will take only about 60-70 days or so.
4. Temperature: Petunias like a warm environment. The most suitable temperature for their growth is: in summer, some varieties can tolerate high temperatures above 35°C, but the plant grows slowly, and most varieties will stop growing. In winter the temperature is 4-10°C. If the temperature is below 4°C, the plant will stop growing, and in a low-temperature environment of -2°C it will not yet be damaged by freezing.
5. Pruning: Generally, petunias do not need pinching, but some varieties do. Pinching can be done when the seedlings are 5-6 cm tall. Generally, no bud thinning is needed throughout the growing period, but sometimes bud thinning is used to control the flowering period. Under high-temperature and humid summer conditions, the plant easily lodges, so pay attention to pruning and shaping, and remove spent flowers, to achieve abundant flowers and lush leaves. If old, diseased or withered leaves are found during its growth, remove them at any time. For old plants that have overwintered, in early spring when repotting, heavy pruning can be carried out; after pruning, apply nitrogen fertilizer once or twice to let them recover and grow and bloom again.
6. Pests and diseases: Common diseases of petunias include white mold, leaf spot, viral disease and aphids, etc.
① White mold: After the disease occurs, promptly remove the diseased leaves, and in the early stage of the disease spray 75% chlorothalonil at 600-800 times dilution.
② Leaf spot: Try to avoid bruising the leaves and pay attention to preventing wind damage, sunscald and freezing injury. Promptly remove diseased leaves and burn them, pay attention to clearing fallen leaves, and spray 50% amobam at 1000 times dilution.
③ Viral disease: The indirect control method is to spray insecticide to control aphids, spraying 40% omethoate at 1000 times solution. Tools and hands that have come into contact with diseased plants during cultivation operations must be disinfected.
④ Aphids: When large numbers of aphids are found, they should be isolated promptly, and sprayed with 10% omethoate emulsion at 1000 times dilution, or malathion emulsion at 1000-1500 times dilution, or dichlorvos emulsifiable concentrate at 1000 times dilution, or Gaobo (70% imidacloprid) water-dispersible granules at 15000-20000 times dilution.