Signet marigold is a wild marigold prolific in Central America. This herbaceous plant produces numerous tiny and yellow to orange flowerheads. The flowers are edible with a lemon-like flavor, perfect for garnishing, tea, and salad. Signet marigold is easy to grow and can be planted near creeks and puddles to repel bugs and insects.
I. Appearance and Characteristics
Tagetes tenuifolia, the signet marigold, golden marigold or lemon marigold, is a species of the wild marigold in the family Asteraceae. It is widespread across most of Mexico as well as Central America, Colombia, and Peru.
Tagetes tenuifolia is an annual herb sometimes reaching as much as 50 cm (20 in) tall. Leaves are less than 3 cm (1+1⁄4 in) long, deeply divided into many small parts. The plant produces many small bright yellow flower heads in a flat-topped array, each head with five ray florets and 7–9 disc florets.
The plant is mildly toxic to humans and pets.
II. How to Grow and Care
Sunlight
The plant needs at least 6 hours of full sun every day.
Temperature and Humidity
Like all marigolds, signet marigolds require warm weather and thrive in heat. The ideal germination temperature for the seeds is between 70 and 75 degrees F. Tender young plants should only be planted after the last frost date in the spring though mature plants at the end of the summer are able to survive a light frost. The plants are not bothered by high humidity.
Soil and Water
Signet marigold grows in a wide range of soil types, including clay, but rich, fertile, well-drained soil with a pH between 6.0 and 7.0 is ideal.
After the plant is established, it tolerates periods of drought. However, for the best bloom, it should be watered regularly in the absence of rain.
Fertilizing
Fertilizing is not necessary—in-ground plants in rich, fertile soil are usually fine without it. If you decide to fertilize to boost flowering, use moderate amounts of all-purpose fertilizer, preferably at diluted strength. Excess nitrogen will produce leaves but few flowers.
Planting Instructions
Select a location in full sun with well-drained, slightly acidic to neutral soil.
You can either start your own signet marigolds from seed or plant potted nursery transplants. Starting seeds indoors 4 to 6 weeks before the last expected frost gives you a head start on the growing season. Plant seeds 1 inch apart in a container of well-drained seed starting mix. Plant seeds ¼ inch deep and keep the soil moist until you are ready to transplant them outside.
Once all danger of frost is past, it is also possible to sow seeds directly into well-worked garden soil. Space seeds 2 to 3 inches apart and plant them ¼ inch deep. Marigold seeds germinate quickly, so expect to see fine, grass-like foliage pop out of the ground about 7 days after planting.
Thin or transplant seedlings 8 to 12 inches apart.
Pruning
If plants become tall, lanky, and look bedraggled, cut them back by half their height, which encourages the growth of new foliage and blossoms.
Propagation
Signet marigolds are propagated from seed as described in the planting instructions above. If you would like to collect the seeds from your plant, make sure it is an open-pollinated variety (most seed companies provide this information in their catalogs) because only those seeds will produce plants that are true to the parent.
Potting and Repotting
Because of their compact size, signet marigolds make excellent container plants. Make sure the container has large drainage holes and fill it with a well-draining potting mix. Like all potted plants outdoors, signet marigolds need regular watering, especially when grown in hanging baskets, as they dry out even faster than standard pots. Repotting is not necessary as the plants conclude their life cycle with the first fall frosts.
Pests and Diseases
The most common pests on signet marigolds are mites, which appear especially during hot weather. Other potential pests include tarnished plant bugs, leafhoppers, leafminers, and slugs. Possible plant diseases are botrytis blight, which occurs especially in wet weather, and leaf spots. Removing infected plant parts often helps to contain them. Aster fusarium wilt is a more serious fungal problem that might require you to remove and destroy the plant before it affects others.
III. Uses and Benefits
- Ornamental uses
There are hundreds of landscape uses for this petite plant. Edge a narrow walkway with the bright blossoms of Signet marigold. Add several plants to a window box for ever-present color right outside your window. Pair it with African and French marigolds for a show of color from early summer until the first frost. Add a group of nectar-rich signets to a garden bed to attract butterflies. Or make signet marigolds part of a deer- and rabbit-resistant container garden.
- Medicinal uses
Some species of Tagetes possess a characteristic scent, which repels insects such as mosquitoes, small animals and smaller, burrowing insects. Tagetes tenuifolia is one of these and is often planted near small creeks or puddle prone areas to repel bugs, especially mosquitoes. It was also found that the Tagetes tenuifolia contains thiophene which is a biocidal compound that acts as a natural pesticide to control nematodes in the field.
- Culinary uses
The plant’s edible flowers can be used as a garnish because of its lemon-like flavor.
- Other uses
Some species of Tagetes possess a characteristic scent, which repels insects such as mosquitoes, small animals and smaller, burrowing insects. Tagetes tenuifolia is one of these and is often planted near small creeks or puddle prone areas to repel bugs, especially mosquitoes. It was also found that the Tagetes tenuifolia contains thiophene which is a biocidal compound that acts as a natural pesticide to control nematodes in the field.
IV. Types of Signet Marigold
- ‘Starfire Mix’
This is a multicolor dwarf variety with single flowers of orange, lemon, maroon, and gold. The compact, 12-inch mound-forming plant is a good choice for containers and hanging baskets.
- ‘Lemon Gem’
At about 10 inches tall, this long-blooming annual makes a great companion plant in the vegetable garden, adding color and attracting pollinators. It is covered with lots of brilliant, almost glowing yellow flowers all summer. The flowers have a citrus scent.
- ‘Tangerine Gem’
The edible petals of this small, bright, prolific bloomer look great as a garnish on salads and other summer dishes. The plant produces tons of single blooms with a plant height of about 10 inches.
- ‘Red Gem’
If you associate marigolds mostly with orange or yellow color schemes, here is a variety that stands out. It produces an abundance of crimson-colored flowers. The compact plants reach only 6 to 12 inches in height and the lacy foliage has a citrus scent.