French Marigold in Zone 6B — Midwest

French Marigolds are a fantastic addition to any Midwest garden. Their vibrant colors brighten up the landscape, and they're surprisingly useful companions for other plants in your vegetable garden, especially tomatoes. Plus, they're relatively low-maintenance, making them perfect for our busy summers and can tolerate those summer heat spells we often get.

Our Midwest weather can be unpredictable, with those variable springs and occasional summer heat waves. But with a little planning and attention to timing, you can easily grow thriving French Marigolds during our 183-day growing season.

Starting French Marigolds indoors is an option, but not always necessary given our fertile soil and the plant's quick growth. If you want a head start, though, begin in mid-March through early April. This gives you about 6 weeks to get them going before transplanting.

Use seed trays with a good seed-starting mix. Provide consistent warmth and plenty of light – a simple grow light works wonders. I like to bottom-water my seedlings to encourage strong root growth and prevent damping off. Keep in mind our moderate-to-late spring, so don't rush to put them out too early.

Transplant your French Marigold seedlings outdoors in late April through early June. Before transplanting, harden them off for about a week. Gradually expose them to outdoor conditions, increasing the time each day.

Space them 8-10 inches apart to allow for good air circulation. Watch out for late frost warnings around transplant time. If a frost is predicted, cover your seedlings with a frost blanket or overturned pots.

Direct sowing French Marigolds is super easy and works great in the Midwest. Wait until mid-April through mid-August to sow seeds directly into your garden beds. The soil should be workable and have warmed up a bit.

Prepare the soil by loosening it and removing any weeds. Sow seeds 8-10 inches apart and lightly cover them with soil. Keep the soil consistently moist until the seedlings emerge. Direct sowing is a great way to get a later crop going for a continuous bloom.

French Marigolds are wonderfully drought-tolerant once established, making them perfect for our Midwest summers. However, they do need consistent watering, especially when young. During the spring, when rainfall is more frequent, keep an eye on the soil moisture.

Use the "finger test" – stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, especially during those summer heat spells. Water at the base of the plants rather than overhead to avoid creating humid conditions around the foliage, which can lead to problems in our moderate-to-humid climate.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can cause yellowing leaves and root rot. A layer of mulch around the base of your plants will help retain moisture and suppress weeds.

Deadheading is key to keeping your French Marigolds blooming all season long. Simply pinch or snip off the spent flowers just below the flower head. This encourages the plant to produce more blooms instead of putting energy into seed production.

Continue deadheading throughout the summer. As the first frost approaches around mid-October, you can stop deadheading and allow the plants to set seed if you want to collect them for next year.

You can expect your first French Marigold blooms to appear from early June through mid-October, about 50 days after planting. Harvest the flowers when they are fully open and their color is most vibrant.

To harvest, simply snip the stem just below the flower head. Regular harvesting encourages the plant to produce even more flowers. As the end of the season approaches and the first frost looms, you can still harvest any remaining blooms. You can also let some of the flower heads dry on the plant to collect seeds for next year.

Here are a few common problems to watch out for with French Marigolds in the Midwest:

Spider Mites

• What it looks like: Fine webbing on the leaves and tiny, spider-like mites on the undersides. Leaves may look speckled and yellowed.
• What causes it: Dry heat is the perfect condition for spider mites.
• How to fix/prevent it: Blast the plants with a strong stream of water from the hose to dislodge the mites. Increase humidity around the plants. Insecticidal soap or neem oil can also be effective.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems. Leaves curl, yellow, and die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it.
• How to fix/prevent it: Improve air circulation through spacing and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays help. Milk spray (1 part milk to 9 parts water) is surprisingly effective. Plant resistant varieties.

Slugs

• What it looks like: Holes in the leaves of young plants, and slimy trails on the foliage and surrounding soil.
• What causes it: Slugs thrive in damp, shady conditions.
• How to fix/prevent it: Handpick slugs off the plants, especially at night. Set out beer traps or use diatomaceous earth around the base of the plants.

Midwest Specific Challenges: Our moderate-to-hot summers and moderate-to-humid humidity can create conditions favorable for both spider mites and powdery mildew, so keep a close eye on your plants and take action quickly if you notice any problems. The wet-summer rainfall can also encourage slugs, especially on young plants.

French Marigolds make excellent companions for several plants in your Midwest garden. They're particularly good friends with tomatoes and peppers, as their scent helps to repel pests like nematodes and tomato hornworms. They also work well with basil, as they attract beneficial insects that prey on aphids.

Cucumbers also benefit from having French Marigolds nearby, as they help deter cucumber beetles. However, avoid planting them near beans-green, as they can inhibit the growth of beans.