Prepared by Karen Russ, HGIC Horticulture Specialist & Bob Polomski Extension Consumer Horticulturist, Clemson University. (New 03/99. Images added 09/07.)
Marigolds are easy to grow, bloom reliably all summer and have few insect and disease problems. They have understandably been a favorite annual in this country for many years.
Plant height varies with the cultivar. Marigolds cover a full range of sizes from about 6-inch dwarves to 3 foot-tall plants.
Marigold flower color ranges from yellow and gold to orange, red and mahogany. Several striped, bicolor and creamy white cultivars are available.
Marigold leaves are finely cut and fernlike. Signet marigolds leaves are much finer than those of other types. Foliage color is a rich dark green and in many cases is scented. In African marigolds, the scent is not pleasant, but some other types are grown for their aromatic fragrance.
Marigolds are used for color massing, edging, borders, cut flowers and container plantings. Most varieties bloom from early summer until hard frost in late fall.
Marigolds require full sun and grow best in well-drained soil with plenty of organic matter. Prepare your flowerbeds by mixing in pine bark or leaf mold to 6 to 10 inches deep.
Marigolds can be purchased as transplants or seeded directly in the garden. Start seed for transplants inside four to six weeks before planting out. Most marigolds are hybrids. If you save seed from last year's plants, they may not be the same as what you grew last year.
Plant each plant slightly deeper than it was in the pack. Plant French marigolds 6 to 9 inches apart and African marigolds up to 18 inches apart. Water thoroughly.
Keep a close check on water during the first 10 to 12 days. After that, water thoroughly once a week if it has not rained at least an inch that week.
Remove the old flowers as they fade for continued bloom. Tall marigolds may require staking to prevent the plants from falling over during storms.
Insects and diseases seldom bother marigolds. Spider mites can be a problem in hot, dry weather. Aster yellows and fungal stem and root rots are occasional disease problems.
Some gardeners plant marigolds in their vegetable gardens to repel harmful insects. Studies have concluded they are not effective in reducing insect damage on vegetable crops. French types may be useful for root-knot nematode control in soil.
African marigolds (Tagetes erecta): These marigolds have large, double flowers from midsummer to frost. Flowers may measure up to 5 inches across. They can grow as tall as 36 inches. African marigolds are excellent bedding plants. Tall varieties can be used as background plantings.
African marigolds are often called American marigolds. Actually, all marigolds are native to subtropical America, and have been cultivated in Mexico for over 2,000 years. Marigolds cultivars are usually sold as part of a series with similar growth characteristics and a wide range of color.
'Park's Whopper', an African marigold with extra large flowers.
Karen Russ, ©2007 HGIC, Clemson Extension
The following series perform well in South Carolina.
French Marigolds (Tagetes patula): French marigolds are small, bushy plants with flowers up to 2 inches across. Flowers may be single or double, yellow, orange, mahogany-red or bicolored. Plant height ranges from 6 to 18 inches. French marigolds bloom from spring until frost. They hold up better in rainy weather than the larger African marigolds.
'Safari Queen' French Marigold
Karen Russ, ©2007 HGIC, Clemson Extension
Signet Marigolds (Tagetes tenuifolia): These are small and bushy with lacy, lemon-scented foliage. Small, yellow, orange, or rust red single flowers cover the plants in summer. Many people who do not like other marigolds admire the delicacy of signets. The flowers of signet marigolds are edible with a spicy tarragon flavor. If bloom slows during midsummer, shear back the plants by one-third to encourage additional blossoms when cool weather returns.
Several less-known marigolds are grown as herbs or for their foliage. The first two may be hardy in warmer parts of South Carolina.
Tangerine Scented Marigold (Tagetes lemonii): The leaves of this southwest native are strongly scented of lemon and mint. Grows 3 feet tall.
Spanish Tarragon (Tagetes lucida): This anise-flavored marigold blooms in fall with many small, simple flowers. This is an excellent substitute for tarragon where the climate is too hot and humid for true tarragon to survive. Grows 3 feet tall.
Irish Lace Marigold (Tagetes filifolia): This is a short plant, with lacy leaves and tiny white florets. It is grown for the beauty and scent of its fine, dark green leaves.
Pot Marigold (Calendula officinalis): Pot marigold is not a true marigold. This cool-season annual is grown for its bright yellow and orange flowers. It can be planted for early spring bloom near the coast or for spring or fall bloom in the rest of South Carolina. Pot marigolds are often grown as herbs.
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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.