Cosmos bipinnatus is the most common type of this annual. Cosmos are extremely easy to care for and are usually pest free. The foliage on a cosmos has fine leaves that grow to about 10 inches in length. They can grow from 1 to 7 feet tall depending on the variety. The flowers come in a variety of beautiful colors with a yellow center and can grow to 2 to 3 inches in diameter. They can be used as background flowers in beds and borders. Cosmos are popular in wildflower and meadow gardens where they are free to sprout and grow anywhere. They are also one of the best nectar plants for attracting butterflies. Most species and hybrids are native to Mexico and the southwestern United States.
Grow cosmos in a sunny location as they require full sun for best growth. Started plants can be bought at local garden centers or they can be started from seeds in the ground after the last frost of the season.
Use average to well drained soil for the cosmos. Use a good planting mix or top soil. Both can be found at a local garden center.
Water the cosmos enough to maintain adequate soil moisture. Water more frequently in times of drought. Fertilize lightly so as not to inhibit blooming.
Pinch or cut with shears the plant tips after the plant has reached 1 ½ feet tall. This will ensure the continual blooming of the plant. The early spring plants will begin to show an abundance of dried seed pods, at this point, cut these plants back to 12 to 18 inches. This will encourage re-bloom in a couple weeks.
Stake with garden stakes or inter-plant with sturdier plants if the cosmos are located in a windy location.