A native of Mexico, marigolds have been grown in gardens throughout the world for hundreds of years. Today, they are one of the most popular bedding plants in the United States. Marigolds are easy to grow, bloom reliably all summer, and have few insect and disease problems. The marigold's only shortcoming (for some people) is its pungent aroma. Iowa State University Extension and Outreach horticulture specialists answer questions about starting and growing marigolds. To have additional questions answered, contact the Hortline at 515-294-3108 or firstname.lastname@example.org.
Two planting options are available when planting marigolds. Most gardeners set out plants in spring. However, gardeners can also sow marigold seeds directly outdoors.
Plant marigold seedlings outdoors after the danger of frost is past. It’s usually safe to begin planting marigolds in late April in southern Iowa and mid-May in northern portions of the state. Plants purchased at greenhouses or started indoors should be hardened or acclimated to outdoor conditions for several days prior to planting. Initially place plants in a shady, protected location and then gradually expose them to longer periods of sunlight.
Sow marigold seeds outdoors when the danger of frost is past. Plant seeds one-quarter inch deep.
Sow marigold seeds indoors six to eight weeks before the intended outdoor planting date. Lightly cover seeds with one-fourth inch of Jiffy Mix or other soilless medium. If given favorable temperatures and moisture conditions, the marigold seeds should begin to germinate in five to seven days.
Planting site requirements for marigolds are full sun and a well-drained soil. The planting site should receive at least six hours of direct sun per day. Poorly drained soils can often be improved by incorporating organic matter (compost, peat or well-rotted manure) into the soil.
While marigolds are seldom bothered by insects and diseases, they are not problem free. Spider mites can devastate marigolds in hot, dry weather. Grasshoppers can also cause considerable damage. Aster yellows is an occasional disease problem. Aster yellows is caused by microorganisms called phytoplasmas. The disease is transmitted from plant to plant by sap-sucking insects, such as leafhoppers. Marigolds infected with aster yellows are stunted, yellow-green in color and their flower buds fail to open. Infected plants should be dug up and destroyed.
Marigolds do not repel rabbits, deer or other animals. In fact, rabbits occasionally browse heavily on marigolds. Erecting a chicken wire or hardware cloth fence around the vegetable garden is the best way to keep rabbits out of the garden.