Mint in Zone 5B — Midwest

Mint is a must-have herb in any Midwest garden. Its refreshing flavor is perfect for summer drinks, and it adds a delicious kick to both sweet and savory dishes. Plus, the satisfaction of snipping fresh mint from your own backyard for a mojito 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 spells. But with a little attention to timing, growing mint is very manageable during our 168-day growing season. You'll be enjoying fresh mint in no time.

Starting mint from seed indoors is possible, but honestly, it's often easier to buy starts or get a division from a friend. If you're determined to start from seed, begin in late February through mid March, about 8 weeks before you plan to transplant outdoors. Use seed trays with a good seed-starting mix, provide warmth, and give them plenty of light, especially since our spring weather is often moderate-to-late in arriving.

Bottom watering your seed trays can help prevent damping-off and keep the seedlings evenly moist. Since we often have cool, damp springs here in the Midwest, it's a good way to avoid overwatering the delicate seedlings.

Transplant your mint outdoors in late April through late May, after the risk of frost has passed. Be sure to harden off your seedlings for about a week by gradually exposing them to outdoor conditions. This is especially important in the Midwest, where we can sometimes get a late cold snap.

Space your mint plants 18-24 inches apart. Keep in mind that mint spreads aggressively, so consider planting it in containers to keep it from taking over your garden. Many Midwest gardeners prefer this strategy. You'll appreciate it later!

Mint loves moist soil, so consistent watering is key, especially during our moderate-to-hot summer heat spells. Aim to keep the soil consistently moist, but not soggy. A good rule of thumb is to water deeply when the top 2 inches of soil feel dry to the touch – the "finger test".

During the wetter parts of spring and the wet-summer rainfall, you might only need to water once a week, if at all. In the heat of summer, you might need to water every other day. Aim for about 1 inch of water per week, either from rain or your hose. Water at the base of the plant to avoid wetting the leaves, as our moderate-to-humid conditions can encourage fungal diseases.

Signs of underwatering include wilting or drooping leaves. Overwatering can lead to yellowing leaves and root rot. A layer of mulch around your mint plants can help retain moisture and suppress weeds, which is especially helpful considering our fertile soil often leads to vigorous weed growth.

Mint requires minimal pruning, but regular harvesting helps keep it in check. The most important thing is to cut back aggressively to control its spread. If you don't, it WILL take over your garden!

Harvest entire stems regularly, cutting them back to just above a leaf node. This encourages bushier growth. As the first frost approaches in early October, give your mint a final haircut, leaving a few inches of growth to help it overwinter.

You can expect your first harvest of mint in late June through mid August, about 60 days after transplanting. The leaves are most flavorful before the plant flowers, so harvest frequently. Pinch off any flower buds to encourage continued leaf production.

To harvest, simply snip off the leaves or stems as needed. Avoid damaging the main stem. Regular harvesting encourages new growth and keeps the plant productive throughout the season.

As the first frost approaches in early October, harvest as much mint as you can and preserve it by drying, freezing, or making mint extract. That way, you can enjoy the taste of summer all winter long.

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 the undersides. Leaves yellow and drop prematurely.
• What causes it: Various rust fungi that thrive in our warm, humid conditions, especially when moisture lingers on the leaves.
• How to fix/prevent it: Remove affected leaves promptly. Avoid overhead watering. Improve air circulation by spacing plants adequately. Consider applying a sulfur or copper fungicide if the problem is severe. Avoid working among wet plants, and rotate crops in subsequent years.

Spider Mites:

• What it looks like: Fine stippling on the leaves (tiny white dots), fine webbing on leaf undersides and between stems, and leaves that turn bronze or yellow.
• What causes it: Tiny arachnids that thrive in hot, dry conditions. Although we don't typically have dry conditions, populations can explode during brief periods of drought stress within our moderate-to-humid summers.
• How to fix/prevent it: A strong spray of water (daily for a week) is often the best treatment. Increase humidity around the plants. Neem oil or insecticidal soap can also be effective. Release predatory mites for a long-term solution. Avoid broad-spectrum pesticides that kill 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. Our fertile soil in the Midwest only exacerbates this tendency.
• How to fix/prevent it: The best solution is to plant mint in containers. If planting in the ground, consider burying a barrier around the planting area to contain the roots. Be vigilant about removing any runners that escape.

Powdery Mildew:

• What it looks like: A 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 – a common pattern in our Midwest summers. Surprisingly, dry leaf surfaces actually favor powdery mildew.
• How to fix/prevent it: Improve air circulation through spacing and pruning. Remove affected leaves. 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 summer heat, moderate-to-humid humidity, and wet-summer rainfall create ideal conditions for rust and powdery mildew. Be vigilant about monitoring your mint plants and taking preventative measures, such as ensuring good air circulation and avoiding overhead watering. Also, keep an eye out for spider mites during any short dry spells we might have.

Mint is a great companion plant for tomatoes and peppers. Its strong scent can help repel pests like aphids and flea beetles that often plague these crops. It also does well near cabbage and broccoli, deterring cabbage moths.

Avoid planting mint near parsley and chamomile. Mint can inhibit the growth of parsley, and chamomile prefers drier conditions than mint can tolerate. Planting them together can lead to competition for resources and reduced yields.