Marigold (Tagetes)

Marigold

Marigolds are brilliant annual bedding plants that add color to any garden. There are several different types, which vary in the size of their flowers, and they come in a range of colors, including yellow, orange, red, mahogany, bicolors and even white. They have a distinctive scent, which many gardeners use to deter whitefly from their other plants by growing marigolds among them.

I. Appearance and Characteristics 

Tagetes () is a genus of 50 species of annual or perennial, mostly herbaceous plants in the family Asteraceae. They are among several groups of plants known in English as marigolds. The genus Tagetes was described by Carl Linnaeus in 1753.

These plants are native to Mexico, growing naturally from Mexico’s valley down to the south and even reaching several other Latinamerican countries, but some species have become naturalized around the world. One species, T. minuta, is considered a noxious invasive plant in some areas.

Tagetes species vary in size from 0.1 to 2.2 m tall. Most species have pinnate green leaves. Blooms naturally occur in golden, orange, yellow, and white colors, often with maroon highlights. Floral heads are typically (1-) to 4–6 cm diameter, generally with both ray florets and disc florets. In horticulture, they tend to be planted as annuals, although the perennial species are gaining popularity. They have fibrous roots.

Depending on the species, Tagetes species grow well in almost any sort of soil. Most horticultural selections grow best in soil with good drainage, and some cultivars are known to have good tolerance to drought.

Depending on the species, marigold foliage has a musky, pungent scent, though some varieties have been bred to be scentless. Due to antibacterial thiophenes exuded by the roots, Tagetes should not be planted near any legume crop. Some of the perennial species are deer-, rabbit-, rodent- and javelina or peccary-resistant.

Marigolds are recorded as a food plant for some Lepidoptera caterpillars including the dot moth, and a nectar source for other butterflies and bumblebees. They are often part of butterfly gardening plantings. In the wild, many species are pollinated by beetles.

II. How to Grow and Care

Sunlight

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.

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.

Watering

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.

Soil

The colorful blossom tolerates barren grounds, which do not have a lot of nutrients in them. On nutrient rich substrates, the plant will grow an increased amount of leaf mass and only little blossoms. That is why fertilizing is only recommended in the cultivation phase, and only very moderately. Concerning balcony plants growing in little earth, a liquid fertilizer low in nitrogen is recommended (At the most every four weeks).

Fertilizing

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.

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.

Propagation

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:

  • Use pruners to clip off 4-inch lengths of supple green stem, preferably without flowers or flower buds.
  • Pull off all leaves from the lower half of the cutting. Also, remove any flowers and flower buds.
  • Dip the cutting in rooting hormone, then plant it about 2 inches deep in a small pot or tray filled with a porous seed-starter mix or a blend of potting soil, sand, and perlite.
  • Tamp the potting medium firmly around the cutting, moisten, then place the pot in a loosely tied plastic bag, creating an informal greenhouse.
  • Place the pot in a warm, bright area, but out of direct sunlight. Every four or five days, lightly moisten the potting mix.
  • When the cuttings have rooted (it usually takes several weeks), transplant the rooted cuttings into larger pots filled with ordinary commercial potting soil. Let them become well established before planting in the garden.

How to Grow 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 directly 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 stopping. 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.

Pests and Diseases

Common Pests and 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.

Common Problems 

Aside from common problems with slugs and snails, 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.

III. Uses and Benefits 

Marigolds make nice border plants, but their hot colors should be used with discretion. They work best with either other hot colors, like yellow and orange daylilies, or with complementary purples, like salvia and verbena. Because most varieties are short plants, marigolds are generally used in the front of a border or in containers. Taller African marigolds, however, are often planted in clumps near the back of the border garden.

Marigold (Tagetes) Details

Common name Marigold
Botanical name Tagetes
Plant type Annual
Hardiness zone 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b, 11a, 11b
Growth rate Fast
Height 1 ft. 0 in. - 4 ft. 0 in.
Width 1 ft. 0 in. - 4 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Clay
Flower color Gold/Yellow
Leaf color Green