Marigold varieties bloom at different times of the year. There are four types of marigolds with many subvarieties. Signet and triploid marigold plants are the least common plants. African and French marigolds are the most common. Marigold varieties need full sun and occasional watering to grow and flower.
African marigolds, also know as American marigolds, make nice bedding or background plants. The plants grow 10 to 36 inches tall with double flowers 5 inches in diameter. In midsummer, the marigold flowers appear in orange to yellow. Flowers remain in bloom until the first frost in fall. Some African marigolds include the Perfection, Inca, Aurora, Crush and Antiqua series.
French marigolds flower in spring. The flowers last until the first hard frost. The plants grow 6 to 18 inches tall with single or double flower heads. The flowers are 2 to 3 inches in diameter with mahogany red, yellow or orange petals. Some French marigold varieties include Janie, Early Spice, Safari, Little hero, Bounty and Boy series. These plants are suitable for borders and containers.
Triploid marigolds, also know as mule marigolds, are reblooming plants but don't produce many viable seeds. These marigold varieties bloom throughout the summer. Triploid marigolds are hybrids made by crossing African and French marigolds. Its flowers are 3 inches in diameter with colours including russet, red, yellow and gold. The Zenith series is one variety of triploid marigold plants that grows 14 to 16 inches tall.
Signet marigolds are used for borders and window boxes. The small, lacy leaves are covered by a single flower. Flowers are orange to yellow and only bloom in summer. The plants grow 8 inches tall and have many tiny little flowers. The leaves are lemon scented, while the edible flowers have a tarragon flavour. Some popular varieties of signet marigolds are Lemon Gem and Golden Gem.