Marigolds are classic annuals planted by American gardeners because they're easy to grow in pretty much any North American climate and are hardy enough to survive even the heat of summer. They just need enough sun and fertile, well-drained soil. It's best to plant them after winter's final frost. Make sure to water them thoroughly at least once a week. Marigold flowers are red, orange, yellow and gold. Most marigolds planted by gardeners in America today are cultivated hybrids.
There are two natural species of marigolds: French marigolds and African (or American) marigolds. French marigolds are smaller and therefore more likely to withstand a storm, whereas African marigolds will probably need to be staked to help them survive in bad weather.
African marigolds are native to Mexico and South America. They have dense, ruffled flowers that grow up to five inches (13 centimeters) in diameter, and have dark green foliage and fine leaves. The African marigold plant can grow up to three feet (90 centimeters) in height but their scent is not very pleasant [source: Clemson Extension Home & Garden Information Center]. African marigolds range in color from yellows and golds to oranges.
French marigolds, in contrast, grow only up to 16 inches (50 centimeters) in height and have smaller flowers. Their colors are in the red and orange family and they're often used as borders for gardens, cut as decoration, or planted in containers. African marigolds are more likely to be arranged toward the back of a gardening bed because of their height.
Although multiple studies have claimed that marigolds have no effect on insects, some gardeners still plant marigolds in an effort to prevent insect infestation in their gardens [source: Clemson Extension Home & Garden Information Center].