Marigolds — part two

Last week the marigold was the subject of this space. We said that the ever-popular annual bedding plant comes in many different varieties and in four basic types: African (American), French, triploid, and signet. Today, we will look closer at the latter three and at general marigold culture.  

The French marigold, (Tagetes patula) is a short marigold with small flowers. Plants range in height from five to 14 inches. Flowers may be single, semi-double, or double, with colors ranging from yellow to orange to bronze and mahogany. Most flower heads are crested, with the center petals standing above the outer petals. The single forms are sometimes called anemones, and are becoming more popular.

Some fine French varieties are Disco Flame, yellow with a mahogany center; Aurora Light Yellow, a semi-double; Janie Primrose Yellow, a double-flowered variety; Bonanza, Safari, Sophia Queen, and many others. 

Triploid marigolds (Tagetes erecta x patula) have the traits of both African and French types-large flowers and a neat growth habit. These hybrids are called triploids because each plant cell has three sets of chromosomes instead of the usual two. Having three sets makes them sterile, like mules. 

Even though they bloom they can’t produce any seeds, so they direct their energy into flowering-from early in the season until fall. One problem, however, with triploids has been their seed’s low viability, which was, until recently, only about 35 percent. Recently, though, breeders have succeeded in developing varieties with germination rates as high as 90%.

Triploid marigolds range from seven to 14 inches tall. Colors range from yellow to gold to orange, plus combinations of these. Flowers may be semi-double or double. 

The least known of the four marigold types is the signet marigold (Tagetes tenuifolia). It has very small, single, yellow or gold-colored blossoms about the size of a penny. The foliage is fine-textured and takes on somewhat of a lemony aroma. 

Plants are dwarf, growing only eight to 10 inches tall. They are profuse bloomers and are good choices for borders. They, like the French and triploids, are day-neutral plants (not sensitive to day length), so they start blooming early in the season and continue blooming to frost.

Signets are creepers, forming low, spreading mats, and look good in hanging baskets. Some good varieties are Lemon Gem, Tangerine Gem, and Paprika.

Marigolds, during the early stages of growth, generally prefer warm days and cool nights (55 degrees), not-too-rich and not-too-wet soils, and a soil pH of about 6.0 to 7.0. Rich soils encourage lush vegetative growth at the expense of flower production, and wet soils make the plant susceptible to the fungus Botrytis cinerea, which causes rotting and discoloring of the petals. The infamous slug also does his best work in wet soils, and can severely damage an otherwise promising marigold crop.

Marigolds are a fine choice for the home gardener. I recommend them highly. Try some!

Tim Lewis is a Georgia Green Industry Association Certified Plant Professional, gardening writer, and former Perry High School horticulture instructor. He can be reached at (478) 954-1507 or timlewis1@windstream.net.