If you are a new gardener, growing Cosmos flowers is a great plant to start with. Fast-growing, there is little that can go wrong when growing this tall plant. The plants are native to Central America and Mexico. They grow quickly to a height of 4-5 feet. Brightly colored single or double flowers include white, pink, orange, yellow, and scarlet.
Cosmos look great at the back of the garden and in informal arrangements.
Flowers Bloom: Summer through Fall
Plant Height: up to 5 feet.
Popular Varieties: Bright Lights, Sea Shells Mixture, Sensation Picotee
The plants are grown from large seeds, making them easy to handle and to plant. Cosmos seeds germinate quickly and never stop from there, normally growing four to five feet in a season.
For good germination, it is important to keep soil moist while germinating.
Sow Cosmos seeds directly into the garden just before the last frost in your area. Space plants 12 inches apart and thin to 18 inches.
While most varieties are annuals, there are perennial varieties. Perennial varieties are Rhizomes and can also be propagated by division.
Days to Germination: 7 – 10 days.
Cosmos plants prefer full sun to partial shade.
The plants do well in both average and poor soils. They are tolerant of dry soil conditions.
Water plants as needed during extended periods of drought.
Add a general-purpose fertilizer once or twice a season.
Keep plants well-weeded when they are young. Then, apply a thick layer of mulch to keep weeds down and to help to retain soil moisture.
Once the flowers bloom, the plant will continue to produce flowers all the way to the first frost. Deadhead spent blooms to keep a neat and tidy appearance. However, if you plan on harvesting seed for next year, keep a few flowers on the plant.
Taller plants may require staking. However, this can be avoided if planted in an area protected from the wind.
Ideal Soil pH: 5.0 – 8.0.
Plant Problems – Identify the causes and find the cures.
Insects and disease problems are very rare for Cosmos. If problems occur, treat early with organic or chemical insect repellents and fungicide.