Native to South America, the marigold is a member of the Compositae family and considered a tender annual when grown in the U.S. The marigold species of plant is capable of growing between 6 inches and 4 feet tall with an equal spread at maturity. The green foliage of the marigold plant gives way to brilliantly coloured orange, yellow, cream or maroon blooms that have rounded or flat heads and a pungent odour. Marigolds propagate by seed. Start seeds indoors prior to the last frost of the to yield healthy seedlings for spring planting.
Fill a seed-starter tray with damp potting soil. Press two to three marigold seeds, 1/4 inches into the soil of each cell. Pat the soil over the top of the seeds to remove air pockets.
Cover the seed starter tray with its matching clear plastic lid. Set the seed tray in an area that receives bright, indirect sunlight and maintain a constant temperature between 15.5 and 23.8 degrees C.
Lift the lid every few days to check the soil for moisture. Keep the soil moist with a misting of water from a spray bottle during the germination period. Marigold seeds should begin to sprout within three to four days of planting.
Remove the plastic lid when the marigold seeds sprout. Continue to maintain bright, indirect sunlight and warm temperatures between 15.5 and 23.8 degrees C as the marigold seedlings grow.
Transplant the marigold seedlings into 4-inch individual pots filled with sterile potting soil, once they develop their second set of leaves. Transplant outdoors in the spring when the threat of frost has passed.
If you do not have access to bright, indirect sunlight or cannot maintain a constant temperature above 15.6 degrees C, set the seed starter tray under a grow light and slip a plant heating pad underneath the seed tray. Marigolds should flower approximately 45 days after seeding, according to West Virginia University Extension.
Do not over water marigold seeds. A light misting is all they need during germination. Soaked soil will prevent germination.