Mint in Zone 6B — Midwest

Mint is a fantastic addition to any Midwest garden. It’s incredibly versatile in the kitchen, adding a refreshing zest to everything from iced tea to summer salads, and it thrives with our fertile soil and adequate rainfall. Plus, there's nothing quite like stepping outside and snipping fresh mint for a mojito on a warm summer evening.

While our Midwest weather can be unpredictable, with cold winters and the occasional summer heat spells, mint is surprisingly resilient. Our 183-day growing season gives you plenty of time to enjoy a bountiful harvest, as long as you plan accordingly and keep an eye on the weather.

Starting mint from seed indoors is possible, but honestly, it's not usually the best route for us Midwest gardeners. Mint seeds can be slow and somewhat finicky to germinate. It's more rewarding to propagate from cuttings or divisions.

However, if you're determined to start from seed, aim for mid February through early March, about eight weeks before you plan to transplant outdoors. Use seed trays with a good seed-starting mix, provide warmth (a heat mat helps), and ensure plenty of light. Bottom watering is key to prevent damping off. Given our moderate-to-late springs, this head start can be beneficial.

Transplanting mint outdoors is best done mid April through mid May, once the risk of hard frost has passed. Before planting, be sure to harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Midwest's variable spring weather.

Space your mint plants about 18-24 inches apart. Honestly, though, because mint spreads so aggressively, most of us plant it in containers to keep it from taking over the entire garden. You can also get starts or divisions from another gardener. Keep an eye on the forecast for any late frosts.

Mint loves moisture, especially during our moderate-to-hot Midwest summers. Aim to keep the soil consistently moist, but not waterlogged. A good rule of thumb is the "finger test": stick your finger about two inches into the soil; if it feels dry, it's time to water.

During the peak of summer, your mint might need about an inch of water per week, either from rainfall or irrigation. Water at the base of the plant to avoid wetting the foliage excessively, as our moderate-to-humid conditions can encourage fungal diseases. Signs of underwatering include wilting leaves, while overwatering can lead to yellowing leaves and root rot.

A layer of mulch, like shredded bark or straw, can help retain moisture and regulate soil temperature, which is especially helpful during those summer heat spells.

Pruning mint is essential to keep it under control and encourage bushier growth. The main goal is to prevent it from taking over your garden! Cut back stems aggressively throughout the growing season to manage its spread.

Harvest entire stems regularly, which also serves as a form of pruning. Pinch off any flower buds as they appear to encourage the plant to focus its energy on leaf production. As the first frost approaches around mid- October, give your mint a final trim, but leave some growth for overwintering.

You can expect your first mint harvest from mid June through early August, about 60 days after transplanting. The best time to harvest is before the plant flowers, as the leaves are most flavorful then. Pinch off leaves and stems as needed.

To harvest, simply snip off stems with scissors or garden shears. Regular harvesting encourages new growth and keeps the plant productive. Remember to pinch off any flower buds to promote continued leaf production.

As the first frost approaches in mid- October, harvest any remaining leaves and stems to dry or freeze for winter use. Even after a frost, the roots will likely survive and send up new shoots next spring.

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

Rust

• What it looks like: Rusty orange, yellow, or brown pustules on leaves and stems, mostly on the 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 immediately. Avoid overhead watering to keep leaves dry. Improve air circulation by spacing plants properly. Apply sulfur or copper fungicide if needed. Don't work among wet plants to prevent spreading. Rotate crops each year.

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 can explode during summer heat spells if the plants are stressed.
• How to fix/prevent it: A strong water spray (daily for a week) is often the best treatment. Increase humidity around plants. Neem oil or insecticidal soap can also help. Release predatory mites. Avoid broad-spectrum pesticides that kill the beneficial predators.

Invasive Spreading

• What it looks like: Mint popping up everywhere you don't want it!
• What causes it: Mint spreads aggressively via underground runners.
• How to fix/prevent it: The best solution is to plant mint in containers. You can also bury a barrier around the planting area to contain the roots. Be vigilant about removing any runners that escape.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes fruit. Leaves curl, yellow, and die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity – all common during our Midwest summers.
• How to fix/prevent it: Improve air circulation through spacing and pruning. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) is surprisingly effective.

Midwest Specific Challenges: Our moderate-to-hot summers and moderate-to-humid conditions can create a favorable environment for fungal diseases like rust and powdery mildew. Be sure to provide good air circulation and avoid overhead watering to minimize these issues. The wet-summer rainfall can also contribute to fungal problems, so monitor your plants regularly and take action at the first sign of trouble.

Mint makes a great companion plant for tomatoes and peppers because its strong scent can help repel pests like aphids and flea beetles. It also benefits cabbage and broccoli by deterring cabbage moths.

Avoid planting mint near parsley or chamomile. Mint can inhibit the growth of parsley, and chamomile has similar growing needs, leading to competition for resources. Keep your mint contained due to its invasive nature, and companion planting will work well.