Marigolds: Durable, Versatile, Colorful

First posted on 06-24-2010

Marigolds are popular, easy-to-grow flowers that also can help fend off pests from your garden.

“This colorful and durable flowering annual asks very little of us as gardeners,” said David Trinklein, University of Missouri Extension horticulturist. The National Garden Bureau (http://www.ngb.org) has chosen the marigold as its 2010 Flower of the Year.

Marigolds are native to the Americas, yet they made their way to U.S. gardens by way of Europe and Africa after Spanish explorers returned with marigold seeds in the 1500s. Therefore, despite their New World origins, two of the most popular ornamental species of marigold are known as African and French marigolds.

The African marigold is characterized by tall plants with large leaves and large double or semidouble flowers. In contrast, French marigolds are dwarf, compact plants between 6 and 14 inches in height.

Marigolds are available to purchase and set out as transplants or you can directly seed them in a garden, Trinklein said. “The seeds are large, easy to handle and germinate reliably in warm, moist soil.”

The plants prefer a loose, well-drained garden loam rich in organic matter. They thrive in the sun and heat and should receive at least six to eight hours of sunshine daily.

As with most flowering annuals, too much fertilizer or very rich soil leads to lush vegetative growth and poor flowering, he said.

Although drought-tolerant, marigolds respond well to supplemental irrigation during dry weather.

Marigolds are relatively pest-free, possibly due to their strongly aromatic foliage, which also makes them a good choice in areas where animal depredation is a problem. Gardeners often use marigolds as companion plants to repel insect pests. Most marigolds produce chemical compounds that repel certain harmful nematodes that sometimes infest garden soil.

Although marigolds are quite durable, there are two diseases that might infect them in gardens: aster yellows and botrytis. Aster yellows is characterized by yellowing of foliage and pale, abnormally shaped buds and blooms. Stunting is common. Infection is spread by leafhoppers. No treatments are available, so the only effective way to manage aster yellows is to remove infected plants.

Botrytis is a fungal disease that attacks many garden plants. Typical symptoms include brown, dying tissue and a grayish mold that produces spores that are spread by wind or water. Although there are preventative fungicides, removing spent flowers from the plant can often provide satisfactory control. This is particularly important near the end of the growing season.

Marigolds adapt well to container gardening, Trinklein said. Many gardeners favor French marigolds for containers because of their smaller size, but don’t overlook African marigolds as a colorful focal point for larger containers. In both cases, good drainage is necessary and can be facilitated by using a soilless growing medium. Always use containers with drainage holes in the bottom or sides.

For information about gardening in your area, contact your local MU Extension center. For information from the National Garden Bureau about marigolds, see http://www.ngb.org/gardening/fact_sheets/fact_details.cfm?factID=28.

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