Tall varieties of African marigold are sometimes planted by stripping off the lower leaves and burying the stems extra deep. This encourages an extra sturdy root system and minimizes the need for staking the plants.
Light
For the most flowers and the healthiest plants, plant your marigolds in full sun. Shady conditions will cause the plants to become leggy and to flower less profusely.
Soil
Marigolds are not fussy. Any good garden soil (and a little water during dry spells) should keep them happy, as long as the soil is not too acidic. Keep the soil pH roughly neutral, from 6.0 to 7.0 . They also don’t need a soil that is particularly rich in organic matter and seem to grow better in a leaner soil.
Water
When you first plant your marigold seeds or plants, make sure they get regular water. Don’t leave them in dry soil for more than a couple of days. If it is particularly hot and sunny, water new plants every day. Once they have had a few weeks to establish a good root system, they will be more drought-tolerant, but they will still bloom best if given weekly water.
Temperature and Humidity
Marigolds are heat-loving plants that thrive in summers throughout their growing range, zones 2 to 11. These true annuals may become a bit subdued during the height of summer, especially in areas with hot summers, but the flowering picks up again when the weather cools in later summer and fall. Marigolds tolerate a wide range of humidity levels, but they may get powdery mildew in damp or humid summers. Planting in full sun and providing room for airflow will lessen this problem. These native plants of Mexico prefer relatively dry air.
Fertilizer
Your marigolds won’t need any supplemental fertilizer unless your soil is extremely poor. The best thing you can do to keep them in flower is to deadhead regularly.
Types of Marigold
There are several species and divisions of marigold, with many cultivars of each. Most are moderate in height, but there is a good amount of variety among the different types. You can find short bedding marigolds that grow only 4 to 6 inches tall and taller varieties that can reach 48 inches and make nice cutting flowers. The three most commonly grown types are African, French, and signet marigolds, representing three different Tagetes species:
African marigolds (Tagetes erecta): With large, pom-pom flowers on medium-sized to tall plants, African marigolds (also known as Mexican marigolds) are popular for both the border and as cut flowers. They can grow up to 4 feet tall and have flowers more than 4 inches across. Colors include yellow and orange. ‘Antigua’ Series are African marigolds with unusually profuse blooms.French marigolds (Tagetes patula); French marigolds are prized for their long, prolific blooms. They tend to be short, bushy plants, from 5 to 18 inches tall. They have purple-tinged stems with double flower heads in yellow, orange, and mahogany that are about 2 inches across. ‘Naughty Marietta’ is a ruffled, deep-yellow French marigold with maroon splashes in the center.Signet marigolds (Tagetes tenuifolia): The edible marigolds are the signets. They look totally different from bedding marigolds, with lacy leaves and small, single, daisy-like flowers. They come in yellow and orange, with fitting cultivar names such as ‘Orange Gem,’ ‘Tangerine Gem’, ‘Red Gem’, and ‘Lemon Gem’. ‘Gem’ Series are single-flowered signets with very fern-like foliage. There have been some hybrids on the market recently with an expanded palette of colors, such as shades of cream, burgundy, and bi-colors, but the flavor is not always equal to that of the ‘Gem’ varieties.
There are also hybrid crosses between T. erecta x T. patula that combine the large flowers of the African marigolds with the more compact stature of the French marigolds.
Pruning
Pinching back the early flower buds will cause a marigold plant to bush out, resulting in a much more dramatic main season of flowering. Regular deadheading of spent blossoms helps to keep the plant producing new blooms well into fall.
Propagating Marigolds
Marigolds are propagated so easily from seed that vegetative propagation is not a very common approach. But if you do want to propagate by rooting stem cuttings, it is very easy to do:
How to Grow Marigolds From Seed
Marigolds are very easy to start from seed. Their large, easy-to-handle seeds are often used for school projects with children. For earliest blooms, you can start seeds indoors, about 6 to 8 weeks before your last frost date, but marigolds germinate quickly outdoors when direct sown into garden soil. You may, in fact, find that last year’s marigolds self-seed so readily that it’s not even necessary to plant new ones. If you choose to start marigold seeds indoors, sow them on the surface of a tray or small pots filled with ordinary commercial potting soil, lightly dampened. Cover the seeds with a thin layer of vermiculite, then cover the tray or pot with plastic. Set the container in a warm location, but light is not needed until after the seeds germinate and sprout. When the seeds sprout (it usually takes just four or five days), remove the plastic and move the container to a location that gets four or five hours of good light daily (artificial light is fine). Keep the potting mix moist but not sopping. To avoid damping-off fungus, it’s best to water from below, by allowing the tray or pot to absorb water from a tray. When the seedlings begin to vigorously generate new leaves, they are ready to transplant outdoors, provided all danger of frost has passed.
Potting and Repotting
Marigolds make excellent outdoor container plants. Use ordinary commercial potting soil in any kind of container—clay pots are especially good. No repotting is necessary, as you’ll be discarding the plant when the growing season concludes.
Overwintering
Marigolds are true annuals that can be pulled and discarded when cold temperatures finally cause them to die. It is fine to leave a few plants to self-seed in the garden. Birds normally don’t eat marigold seeds, though they sometimes do tear apart the flower heads, which can assist in the self-seeding effort.
Common Pests & Plant Diseases
Marigolds are free of most serious pests and diseases, but some problems occasionally do occur:
Snails and slugs may eat leaves, especially on young plants. If you notice ragged holes in leaves, this is likely the problem. Keep the soil free of leaf debris, and set out slug and snail traps, if needed.Aphids can sometimes be a problem, but horticultural soaps or oils easily handle them.Powdery mildew is a fungal disease that is common to marigolds. The white residue that appears on leaves is usually caused by fungal spores that splash up from the ground, or between affected plants. The disease is unattractive but almost never fatal. Prevent it by providing good air circulation between plants, and by watering by ground-soaking rather than by overhead spraying.
How to Get Marigolds to Bloom
Marigolds rarely need to be coaxed into bloom, but there are several cultural practices that will make the flowers larger and more prolific:
Make sure the plants have plenty of direct sunlight. Marigolds growing in shady conditions will flower less robustly.Deadhead spent flowers promptly. Removing old flowers will stimulate the plant into producing additional buds and blooms.Pinch back the tips of young plants before they bloom. While this can delay the onset of blooming, it also forces the plants into bushier growth, which ultimately will produce many more flower buds and blossoms. As buds do appear, pinch off half of them to make the remaining buds and flowers larger.Don’t overfeed. Marigolds need little if any fertilizer and excess feeding can actually reduce the flowers, forcing the plant to put its energy instead into foliage growth.
Common Problems With Marigolds
Aside from common problems with slugs and snails (see above), gardeners have only a few other issues with marigolds.
Seedlings Die Shortly After Sprouting
Although marigolds are very easy to grow from seeds, it’s not uncommon for gardeners to have problems with the seedlings dying off quickly just as they are starting to grow, usually when the fragile stems turn black, wither, and die. This is a classic example of “damping off disease”—a fungal disease caused by many different fungi species. There is no cure for damping off disease, but you can prevent its occurrence by using only sterile potting mixes, by using clean pots, by providing good air circulation and plenty of space between seedlings, and by watering seedling pots and trays from below rather than by overhead watering. Damping-off fungi tend to prefer cool conditions, so keeping seedling trays warm may also help prevent it.
Tall Marigolds Flop Over
The taller varieties of marigolds that grow 3 feet tall or more can get top-heavy and flop over due to winds and heavy rains. To prevent this, you can bury the plants extra-deep when planting, stripping off the lower leaves and planting so these exposed stem nodes are buried. This creates an extra-large root system that may be enough to hold the plant upright, even in moderately strong winds. It also helps to remove heavy spent flowers immediately after blooming, to prevent the plant from becoming too top-heavy. And, of course, you can stake up your plants if needed.
Plants Get Weak in Midsummer
Marigolds can sometimes get sparse and spindly with reduced blooming during the hottest part of mid-summer. This is especially likely in very hot climates. Many gardeners prefer to sharply prune back the plants as these hot stretches begin. The plants almost always come back strong and produce good growth and profuse flowering as the weather begins to cool again in late summer and early fall.
