French Marigold (Tagetes patula)
The French marigold is native to Mexico and Nicaragua. In addition, it has been cultivated in Europe and the United States for its flowers and medicinal properties. The plant can grow in soil types from sand to clay, but requires well-drained soil. It is hardy to zone 9, is frost tender, and performs best in full sun.
The flower is an annual, growing to 10″ by 15″. Flowering from July to October, the seeds ripen in September. The flowers are perfect (having both male and female organs) and are pollinated by insects. They are noted for attracting wildlife.
French Marigold (T. patula) has roots that exude a substance which spreads in their immediate vicinity killing nematodes. For nematode control you want to plant dense areas of them. There have been some studies done that proved this nematode killing effect lasted for several years after the plants were These marigolds also help to deter whiteflies when planted around tomatoes and can be used in greenhouses for the same purpose. Whiteflies hate the smell of marigolds. Do not plant French marigolds next to bean plants.