Sun-loving plants that light up the garden with bright shades of orange, gold, yellow and mahogany, marigolds (Tagetes spp.) bloom brightly throughout summer and fall. Marigolds come in petite varieties that top out at 6 inches, to giant varieties that reach heights of 3 to 5 feet. Most often grown as annuals, some species of marigold grow year-round in the warm climates of U.S. Department of Agriculture plant hardiness zones 9 through 11.
As a general rule, marigolds don't need fertilizer. If your soil is extremely poor or growth appears weak, fertilize the plants lightly with a dry, 5-10-5 fertilizer every six weeks. Apply the fertilizer at a rate of 1 teaspoon per 1 square foot of planting space, or 2 pounds per 100 square feet. Sprinkle the fertilizer on the soil around the plants, and then water deeply. Never allow the fertilizer to touch the flowers, leaves or stems. Feed potted marigolds once every month using a water-soluble fertilizer mixed at a rate of 1 tablespoon of fertilizer to 1 gallon of water. Always read the label as application rates and instructions vary by brand.
Too much fertilizer often overstimulates growth. Although the resulting rich foliage is attractive, it comes at the expense of flowering, which may decrease markedly. Also, the lush growth is weak and tender and more prone to disease and damage by pests. Too much fertilizer can also burn the roots, especially during hot summer weather. Scorched roots may kill the plant.
Although marigolds tolerate poor, dry soil, they perform best in loose, well-draining, moderately fertile soil with a pH between 6.0 and 7.0. Don't add fertilizer to the soil at planting time. Instead, dig a 3 to 4 inch layer of organic material, such as compost, bark chips or pine needles, into the top 6 to 8 inches of soil. Organic materials, which enrich the soil without burning the roots, improve drainage and help to maintain the proper soil pH. Marigolds require at least six to eight hours of sun per day.
Pinch young marigolds once or twice to force the plants to branch out, creating a fuller, bushier plant. Similarly, deadhead blooms as soon as they wilt to encourage continued blooming throughout the season. Marigolds benefit from about 1 inch of water per week during warm weather, or enough to saturate the soil to a depth of about 6 to 9 inches. Avoid overhead watering and keep the foliage as dry as possible. Instead, use a soaker hose or water by hand. If you use a sprinkler, water the plants in the morning so the foliage dries before evening. Spread a 2- to 3-inch layer of mulch around the plant, but limit mulch to 3 inches or less as mulch may harbor slugs that feed on tender foliage. If you notice slugs, pick them off by hand or apply slug bat at a rate of 1 teaspoon per 1 foot of planting area. Check the label on the slug bait because instructions and rates vary.
- Floridata: Tagetes Spp.
- The Old Farmer's Almanac: Marigolds
- University of Illinois Extension: Gardening With Annuals: Fertilization
- Scotts Miracle-Gro: Miracle-Gro Water Soluble All Purpose Plant Food
- National Gardening Association: Effects of Over-Fertilizing Marigolds
- Oregon State University Extension: Fertilize Fading Annuals
- The Gardener's A-Z Guide to Growing Flowers From Seed to Bloom; Eileen Powell
- Missouri State University Extension: The Marvelous Marigold
- Purdue University Extension: Growing Annual Flowers
- University of Minnesota Department of Entomology: OR-Cal Slug and Snail Bait
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