Mexican Aster Fast Facts


Mexican aster (Cosmos bipinnatus) likes full sun and tolerates dry, porous soil. This annual flower grows 48 inches high and spreads up to 24 inches wide. Pink, red and white blossoms bloom from summer into the fall.


Plant seeds after all frost danger have past. Seeds germinate in 1 week when temperatures are from 68 to 86 degrees F. Blooms appear in 2 to 3 months.


Pinch the plant back early to encourage branching and plant density.


Stake or support your Mexican asters since they tend to flop over due to their height.


Over-fertilizing will cause the Mexican asters to produce heavy foliage instead of flowers.


Mexican asters are susceptible to bacterial wilt, powdery mildew, leaf spots, aphids and Japanese beetles.


Mexican asters are popular as cut flowers. It makes a dramatic landscape plant as well.


  • Michigan State University Extension: Cosmos bipinnatus -- Mexican Aster
  • University of Florida Cooperative Extension Service: Cosmos bipinnatus
Keywords: Cosmos bipinnatus, Mexican asters, cut flower

About this Author

Karen Carter spent three years as a technology specialist in the public school system and her writing has appeared in the "Willapa Harbor Herald" and the "Rogue College Byline." She has an Associate of Arts from Rogue Community College with a certificate in computer information systems.