One problem with the triploids is their low seed germination rate. Average germination is around 50 percent. Since the triploid hybrids are unable to produce viable seed, they also are known as mule marigolds. Signet marigold plants are bushy with fine, lacy foliage. The small, single flowers literally cover the plants in summer.
Flower colors range from yellow to orange.
They also are edible. The flowers of signet marigolds have a spicy tarragon flavor. The foliage has a pleasant lemon fragrance. Signet marigolds are excellent plants for edging beds and in window boxes. The varieties Lemon Gem, Golden Gem and Tangerine Gem do well in Iowa.