The French marigold, "the most popular source of yellows and oranges in bedding schemes" according to "The Bedding Plant Expert," traveled from its native territory in Mexico to Spain and thence France right after the discovery of the New World. The hardy, supremely easygoing Tagetes patula (patula means "spreading") remains a favorite throughout the United States, Mexico and Europe as well as in India, where it provides flowers for weddings and festivals.
French marigolds, "robust and dependable" according to Bob Hyland in "Designing Borders for Sun and Shade," provide single, semidouble and double blooms on plants about 9 to 18 inches high. French marigolds may be used for root-knot nematode control in soil.
In mild areas, sow seed outdoors in May or after the last frost where they are to grow. For a head start, sow seeds indoors or in an outdoor cold frame 4 to 6 weeks before the last frost. Seeds germinate at 70 to 75 degrees F within 7 to 14 days.
Use any good garden soil, especially if enriched with humus and well drained. Use potting soil for planter boxes. French marigolds tolerate dry soil but prefer moist.
Place French marigolds in full sun. Space 6 to 8 inches apart.
Plant out before the first flowers open. Remove opened buds for the first couple of weeks after planting
Water when the weather is dry and keep watch for slugs. Dead-head (remove faded and dead blossoms) to prolong the display, which will continue until first frost
French marigolds bloom in as little as 6 to 7 weeks after spouting. These hardy plants also self-sow, meaning they will sprout again from pinched dead blooms the following spring. Or you can gather seed for the next year's planting