Marigold

Marigolds (Tagetes species) are easy, cheerful annuals that bloom reliably all summer and have few insect or disease problems. They’re native to the Americas, from the southwestern United States to South America, and because they sprout quickly they’re an excellent choice if you’re new to growing flowers from seed.

Three main types. French marigolds (T. patula) are compact plants with smaller flowers, and African marigolds (T. erecta) are larger plants with blooms up to 4 inches (10 cm) across. Signet marigolds (T. tenuifolia) are small, bushy plants with lacy, lemon-scented leaves.

Size depends on the type. French marigolds usually grow 6 to 18 inches (15–46 cm) tall, while signets rarely grow taller than 12 inches (30 cm). African marigolds are the tallest, reaching about 3 feet (91 cm) and sometimes 4 feet (122 cm). Check your seed packet for the height of your variety.

Start seeds indoors for earlier flowers. Sow seeds indoors four to six weeks before you plan to plant them outside, or about 8 weeks ahead for African marigolds. Cover the seed lightly and keep it warm: gardening experts suggest 70–75 °F (21–24 °C), and at 75–80 °F (24–27 °C) seedlings usually appear in 4 to 7 days.

Or sow straight into the garden. Once the soil has warmed and there’s no more danger of frost, sow seeds outdoors about ¼ inch (6 mm) deep. Expect them to come up in 5 to 7 days.

Plant out after the last frost. The best time to plant marigolds outside is after the last spring frost. Space French marigolds 8 to 10 inches (20–25 cm) apart and African marigolds 12 to 16 inches (30–41 cm) apart.

Pick a sunny spot. Marigolds need full sun and grow best in loamy soil that drains well. Planted in shade or in cool, damp places, they won’t bloom well and are prone to powdery mildew.

Pots work too. Marigolds are good in containers and window boxes. Use a soilless potting mix with slow-release fertilizer, and space the plants so they aren’t crowded.

Watering. Water well at planting and keep the soil evenly moist for the first couple of weeks. Once established, marigolds do well with about 1 inch (2.5 cm) of water a week; if it doesn’t rain, water deeply once a week and let the soil dry a little in between. Water at the base of the plant so the leaves stay dry.

Deadheading and pinching. Remove faded flowers to keep new ones coming. Pinching young plants encourages them to branch.

Support. Tall African marigolds may need stakes so storms don’t knock them over.

Summer heat. Very hot weather can make plants stall for a while, with less growth and fewer flowers.

Marigolds are said to repel pests, but some insects are attracted to them: spider mites (especially in hot, dry weather), slugs, leafminers, aphids, whiteflies, thrips and caterpillars. Insecticidal soap, used as the label directs, usually solves spider mite and aphid problems.

Diseases turn up occasionally, including fungal leaf spots, stem and root rots, gray mold (botrytis) and bacterial wilt. Viruses spread by insects can cause spotted or yellowed leaves and stunted growth. Powdery mildew is more likely when conditions are too wet or humid, and African marigolds may be prone to it.

If your soil pH is below 5.5, the leaves can develop a bronze, speckled look.

For cut flowers, pick blooms when they’re fully open but their centers are still tight. For cutting, gardening experts recommend the tall varieties.

To save seed for next year, collect it from open-pollinated varieties only. Seed from hybrids may be sterile or may grow into plants that don’t look like the parent.

Marigold sap can irritate skin. Gardening experts list marigolds as a low-severity poison: sap on broken skin, together with sunlight, can cause redness, burning pain and blisters. Gardening experts say African marigold foliage may aggravate skin allergies and recommends gloves.

Sources disagree about eating the flowers. Gardening experts say Tagetes flowers are generally considered inedible, and that the edible “pot marigold” is a different plant, Calendula officinalis. Gardening experts say signet marigold blooms are edible, and marigolds can be harmful if eaten in large amounts.