Marigolds are used for mass planting, edging, borders, cut flowers, and container plantings. There is often a long blooming season for most species, from early July to late fall’s strong frost.
Marigolds require full sun and grow best in well-drained, loamy soil. Put organic stuff into the soil and dig it in to a depth of about 6 inches before planting flowers. Before planting, amend the soil with the results of a soil test for optimal results. Please refer to HGIC 1652, Soil Testing, for instructions on how to submit a soil sample for analysis. Marigolds thrive in soil with a low pH. The leaves of marigolds can become bronzed and spotted if the soil pH is less than 5.5, which can be caused by the presence of poisonous levels of manganese or iron.
In the absence of soil test results, a slow-release fertiliser formulated for annuals can be incorporated at the time of planting. Marigolds should be planted in the spring once the danger of frost has passed. Plants should be spaced in accordance with their expected mature size. Plant French marigolds at an 8–10-inch spacing and African marigolds at a 12–16-inch distance. To learn how to get your garden ready for marigold planting, read here.