How to Grow Cosmos from Seed? A Detailed Guide to Planting Methods
Cosmos is an annual or perennial herbaceous plant of the genus Cosmos in the Asteraceae family, native to Mexico. After Columbus discovered the New World, sailors collected its seeds and brought them back to Europe to plant. Because it is lovely in appearance and easy to cultivate, it quickly spread from gardens to the countryside and mountain forests, taking root across the European continent. Now let us take a look at how to grow cosmos from seed!
Sowing Time
If cosmos is to bloom in summer, it should be sown from February to March in early spring, preferably under conditions where both temperature and humidity can be controlled. If sowing in the open air, it should be done in mid-April when the temperature is suitable; when the temperature is right, seedlings will emerge in about a week.
Sowing Medium
For the sowing medium of cosmos, choose loose soil rich in organic matter, and apply a certain amount of decomposed organic fertilizer before sowing. When sowing, mix the seeds evenly with a certain amount of sand and scatter them evenly over the seedbed, then cover with about 1 cm of soil. After sowing, keep the soil moist; germination will occur when the temperature is kept at around 18°C.
Seedling Stage Management
When cosmos seedlings grow 4 to 5 true leaves, they can be transplanted into nutrient pots and pinched. During the seedling growth period, no additional topdressing is needed, so as to avoid excessive vegetative growth of branches and leaves that would affect flowering.
Growth Period Management
The cosmos plant is relatively tall, with slender stems and large, beautiful flowers. When exposed to wind or other harsh weather, it tends to fall over, which affects its ornamental value. Therefore, cosmos needs to be pinched multiple times throughout its growth process, and watering should be reduced. This not only promotes branching but also dwarfs the plant, preventing lodging during growth.
Pest and Disease Control
1. Red spider mite: Cosmos is prone to red spider mites in hot, dry conditions. Whether you like it or not, cosmos has a high probability of getting red spider mites; even if you plant only two, they may still appear. They should be detected and controlled early. At the initial stage, spray a 1000 to 1500 times dilution of 40% dicofol emulsifiable concentrate.
2. Powdery mildew: Do not plant too densely, and maintain good ventilation and light transmission. After the disease occurs, promptly prune and destroy diseased leaves and plants to strictly prevent reinfection. At the initial stage, spray a 1500 times dilution of 15% triadimefon wettable powder, or a 1200 to 1500 times dilution of 10% lewubing wettable powder. Alternate the two chemicals and spray 2 to 3 times consecutively.