Growing marigolds – part one

Marigolds are popular flowering annuals grown in America today. Natives of Mexico, South America, and the southwestern United States, the marigold (genus Tagetes) is heat and drought tolerant as well as floriferous.

Tradition has it that marigolds repel insects, rabbits, and other pests. Not really. However, there is research to indicate that marigolds have the ability to repel nematodes, those microscopic, worm-like pests that inhabit the soil and feed on the roots of many plants. There are several types of nematodes, but the type which is the most troublesome to gardeners and farmers is the root-knot nematode. French marigolds, a small-flowering type of marigolds, are somewhat effective against them. 

There are basically four types of marigolds-signet, French, African/American, and triploids. Let’s look at one type today.

Tagetes erectas are generally tall marigolds with one flower per stem. Traditionally called African marigolds, some seed catalogs refer to them as American types, due to the 1959 campaign by W. Atlee Burpee Co. president, David Burpee, to change the name. Some tall varieties reach as high as three feet, displaying their single flower well above the foliage. These may need staking, and you may want to hide their long stems with other flowers. Other varieties are not so tall, reaching only 12 to 18 inches in height, and some grow to only 8 to 10 inches. 

Blossoms of all T. erecta varieties are double, and make excellent cut flowers if you remove the foliage, which easily rots in water. Blossoms range from two to five inches in diameter, and in color, from white to yellow to gold to orange.

African/American marigolds have all been, until recently, relatively late bloomers. Classified as short day plants, if they received more than nine hours of light per day during their first four weeks of life, they put their energy into growing vegetatively rather than in producing flowers. To get them to bloom earlier, gardeners and commercial growers had to expose them to dark periods, which was troublesome and costly. Plants treated this way bloom in 10 weeks after germination; without it, they wouldn’t oblige the grower until late summer.   

The fairly recent development of day-length neutral marigolds negates this late-blooming phenomenon. Such varieties are easier to bring into bloom and will flower in 10 weeks even if exposed to long days. We gardeners in the South will be able to plant them in August for October bloom. 

Next: More on marigolds.