Plant Common Name
There are approximately 50 species of Tagetes. This New World genus originates from the warm regions of the southwestern United States, Mexico and South America. The plants are variable and may be annual, perennial or shrub-like. Most have strongly scented leaves and showy flowers. They were first brought to the Old World in the 16th Century where they became valued both ornamentally and medicinally. Most cultivated varieties available today are complex hybrids that provide an abundance of pretty flowers.
The plants vary widely in size but are usually upright and bushy. They have robust green leaves dotted with glands that hold aromatic oil. The lobed leaves may be smooth or hairy and are often so deeply divided they are ferny. The flowers are usually very showy. They may be yellow, orange, gold, red-brown, white or bi-colored and are either ruffled and double or single and daisy-like. They are borne at the ends of stems, either singly or in branched groups. The flower heads sit atop distinctive hollow, bell-shaped stems. The dry, brown seedheads eventually shatter and release many linear black seeds with hairs at the top.
Marigolds are much beloved by gardeners and have become highly cultivated. Most of the varieties grown today are annuals and complex crosses of three species, Tagetes erecta, T. patula and T. tenuifolia. There are hundreds of selections with varying heights, flower sizes and colors. These have been divided into groups according to parentage:
1. African marigolds are mostly derived from Tagetes erecta and are American in origin rather than African. They are tall, stout and bushy and have large ruffled flowers that are dense and carnation-like. Their toothed leaves are ferny and stems hairless.
2. French marigolds are mostly derived from the American species, Tagetes patula. They are compact, bushy and offer lots and lots of smaller flowers that may be single, double or semi-double. The leaves are lance-shaped and ferny.
3. Signet marigolds are derived from Tagetes tenuifolia. These broadly mounded annuals generally have single flowers that are smaller and numerous. Its fine foliage is lacy and bright green.
Marigolds are gloriously easy to grow. Most are happiest in full sun and average, well-drained soil. They are cold sensitive and should be planted after the last frost date. Most are heat tolerant and can withstand periods of drought. Marigolds are wonderful summer annuals in most locations, however in tropical and sub-tropical regions the combination of heat, humidity and abundant rain can induce rot and cause them to melt. In these areas, they are better planted in fall and late winter. Regular deadheading will encourage season-long bloom and keep plants looking neat and clean.
These are some of the best bedding and container plants around. As an added benefit, research suggests that their roots, particularly those of Tagetes patula, emit a substance that deters root-damaging nematodes, which plague certain vegetable crops. Consequently, they are favored as companion plants in vegetable gardens.