Marigolds are hardy, annual flowers that can grow anywhere from 6 inches to 4 feet tall. Each plant can spread up to two feet across and will bloom all summer long. Marigolds range from cream and yellow to orange and maroon. The flowers are very easy to grow when they are provided with well-drained, moist soil and plenty of sunshine. Pests are usually not a problem with marigolds but they can be susceptible to spider mites and spittlebugs.
Plant marigold seeds indoors in peat pots in early March where they will not be exposed to a threat of frost. Place the seeds on top of the soil and then lightly cover them with the all-purpose potting soil. You do not want the seeds to be covered too deeply in the soil. Use no more than 1/8 inch of soil on top of the seeds.
Sprinkle the newly planted seeds lightly with water. This will help keep the seeds from blowing away and will provide enough water for germination. You do not want the soil to be soaked. Instead keep the soil slightly moist and do not allow them to dry out before you re-water the plants.
Place the seedlings in a bright, sunny window. For best results, the plants should get sunlight for at least 8 hours a day. If you cannot find a location that will allow them this much sunlight, a heat lamp will work for a portion of the time. Plants will begin to flower approximately 45 days after you have planted them; this will usually occur after they have been moved outside.
Transplant your seedlings in early May when there is no longer a threat of frost. Plants should be planted at a minimum of 6 to 9 inches apart from one another for the dwarf French marigolds and 18 inches apart for the larger American Golds. They will spread out begin to blend together as the summer progresses. The flowers will begin to bloom very quickly after they have been placed outside in beds.
Pinch off any blooms that have died. More blooms will take the place of the ones that have died out and the flowers will continue to bloom until the first frost in early fall. If you have planted the taller varieties of marigolds you may have to provide the plant with stakes to prevent the flowers from falling over and breaking.