Mint in Zone 7A — Midwest

Mint is a fantastic addition to any Midwest garden. Its refreshing flavor elevates everything from summer drinks to savory dishes. Plus, the satisfaction of snipping fresh sprigs for your iced tea on a warm summer evening is hard to beat.

Our Midwest weather can be unpredictable, with temperature swings in spring and the occasional summer heat spell. But with a little attention to timing, you can easily grow mint during our 193-day growing season.

Starting mint seeds indoors isn't essential, as it's easily propagated from cuttings or divisions. But if you're eager to get a head start, aim for early to late February. This gives the seedlings about 8 weeks to develop before transplanting outdoors.

Use seed trays with good drainage and a well-draining seed-starting mix. Provide warmth with a heat mat and ensure adequate light, either from a grow light or a bright, sunny window. Bottom watering is a great way to keep the soil consistently moist without overwatering the delicate seedlings. Remember, our Midwest springs can be moderate-to-late, so be patient!

Transplant your mint seedlings outdoors from early April through early May, once the danger of hard frost has passed. Before transplanting, harden off the seedlings by gradually exposing them to outdoor conditions for about a week. Space them 18-24 inches apart.

Mint is known for its aggressive spreading habit, so consider planting it in containers to keep it contained. You can also get starts or divisions from other gardeners. Keep an eye on the weather forecast around transplant time; we sometimes get a late frost in the Midwest, so be prepared to cover your plants if necessary.

Mint thrives in consistently moist soil, which is good because our Midwest summers can bring heat spells. Aim to water deeply once or twice a week, providing about an inch of water each time. Use the "finger test" to check soil moisture – stick your finger about 2 inches into the soil; if it feels dry, it's time to water.

Water at the base of the plant rather than overhead to minimize the risk of fungal diseases, especially with our moderate-to-humid conditions. Overwatering can lead to root rot, indicated by yellowing leaves and a generally unhealthy appearance. Underwatering will cause wilting and dry, brittle leaves. A layer of mulch around the base of the plant helps retain moisture and regulate soil temperature, which is helpful during our summer heat.

Mint requires minimal pruning, but regular harvesting keeps it productive and prevents it from flowering, which can diminish the flavor of the leaves. Cut back entire stems as needed throughout the growing season. Don't be afraid to prune aggressively; it encourages bushier growth and helps control its spread.

As the first frost approaches around mid- October, you can cut back the remaining foliage to the ground. The plant will go dormant and return in the spring.

You can expect your first harvest of mint from early June through late July. The leaves are most flavorful before the plant flowers. Harvest leaves and stems anytime they're large enough to use. Pinch off any flower buds you see to encourage continued leaf production.

To harvest, simply snip off stems with scissors or pruning shears. Avoid pulling on the plant, as this can damage the roots. Regular harvesting encourages bushier growth and prevents the plant from becoming leggy. As the end of the season nears and our first frost approaches, harvest as much mint as you can and preserve it by drying, freezing, or making into pesto.

Here are some common problems you might encounter with mint in the Midwest:

Rust

• What it looks like: Rusty orange, yellow, or brown pustules on leaves and stems, mostly on undersides. Leaves yellow and drop prematurely.
• What causes it: Various rust fungi that spread via wind-borne spores. Favored by our warm, humid conditions with moisture on leaves.
• How to fix/prevent it: Remove affected leaves. Avoid overhead watering. Improve air circulation. Apply sulfur or copper fungicide. Don't work among wet plants. Rotate crops.

Spider Mites

• What it looks like: Fine stippling on leaves (tiny white dots). Fine webbing on leaf undersides and between stems. Leaves turn bronze or yellow.
• What causes it: Tiny arachnids that thrive in hot, dry conditions. Populations explode during our occasional drought spells.
• How to fix/prevent it: Strong water spray (daily for a week) is the best treatment. Increase humidity around plants. Neem oil or insecticidal soap. Release predatory mites (Phytoseiulus persimilis). Avoid broad-spectrum pesticides that kill predators.

Invasive Spreading

• What it looks like: Mint popping up everywhere you don't want it.
• What causes it: Underground rhizomes spread aggressively.
• How to fix/prevent it: Plant in containers. Sink a barrier (like plastic edging) around in-ground plantings. Vigilantly remove unwanted shoots.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes fruit. Leaves curl, yellow, and die. Reduces plant vigor.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity, which we often experience in the Midwest.
• 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.

Midwest Specific Challenges: Our moderate-to-hot heat, moderate-to-humid humidity, and wet summers create conditions that can favor fungal diseases like rust and powdery mildew. Be vigilant about monitoring your plants and taking preventative measures.

Mint is a great companion plant for many vegetables. It helps repel pests from tomatoes and peppers. It can also improve the health of cabbage and broccoli.

Avoid planting mint near parsley and chamomile. Mint can inhibit the growth of parsley. Chamomile prefers drier conditions, which is the opposite of what mint likes.