Tagetes erecta - African Marigold. Tagetes patula - French Marigold. Tagetes tenuifolia - Marigold gems.
Very easy to grow. Start inside 6-8 weeks before last frost. Start African types earlier than French types. Cover seed with 1/4 inch of soil and provide an average soil warmth of 24deg;C (75°F). May also be direct seeded about 2 weeks before last frost. Transplant after last frost into a sunny location. Will grow well in poor soil. Space African types 12-18 inches apart, and French types 6-8 inches apart. Deadhead regularly.