Cosmos bipinnatus, commonly called the garden cosmos or Mexican aster, is a medium-sized flowering herbaceous plant native to Mexico. The species and its varieties and cultivars are popular as an ornamental plant in temperate climate gardens. It can also be found in natural areas in much of North America, where it is a garden escape and in some habitats becoming a weed.
Dahlia is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae [or Compositae], dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 2 in [5.1 cm] diameter or up to 1 ft [30 cm] or “dinner plate”.