Mint in Zone 5B — Great Plains

Mint is a fantastic addition to any Great Plains garden. The fresh, vibrant flavor is perfect for teas, summer drinks, and adding a zing to both sweet and savory dishes. Plus, the invigorating scent is a welcome treat on those hot summer days we often get here.

Our region can throw some extreme weather at us, but don't let that deter you. With a good plan, you can easily enjoy a bountiful mint harvest within our 178-day growing season. Timing is key, and we'll walk you through it.

Starting mint from seed indoors is an option, but honestly, it's often easier to buy a start from a local nursery or get a division from a friend. If you're set on starting from seed, begin in mid February through early March, roughly 8 weeks before you plan to transplant. Use seed trays with a good seed-starting mix, provide warmth (a heat mat helps), and give them plenty of light (grow lights are ideal).

Water from the bottom to avoid damping off – set the tray in a shallow dish of water until the soil surface is moist. Keep in mind, spring in the Plains can be quite variable, with temperature swings that can stress young seedlings. So, monitor them carefully and adjust conditions as needed.

Transplant your mint outdoors from mid April through mid May, after the last expected frost. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature fluctuations common in our region.

Space your mint plants 18-24 inches apart. Be warned: Mint spreads aggressively. Planting in containers is highly recommended to keep it from taking over your entire garden. You can sink the container into the ground for a more natural look. Keep an eye on the weather forecast around transplant time. A late frost or sudden temperature drop can set your plants back.

Mint loves moist soil, which can be a bit of a challenge in our Great Plains climate, especially with our variable rainfall. During the heat of summer (when highs can easily reach 93°F), you'll likely need to water your mint deeply a couple of times a week, providing about 1 inch of water each time. Use the finger test: stick your finger into the soil about 2 inches deep. If it feels dry, it's time to water.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases, even with our low-to-moderate humidity. Overhead watering is fine, but do it in the morning so the leaves have time to dry out during the day. If the leaves start to droop or turn yellow, you might be overwatering. If they look dry and crispy, you're probably underwatering.

A layer of mulch around your mint plants can help retain moisture and suppress weeds. Straw, shredded bark, or even grass clippings work well in our region. Just be sure to leave a little space around the stems to prevent rot.

Pruning mint is more about control than anything else. Mint is vigorous and will spread rapidly if left unchecked. Throughout the growing season, regularly harvest entire stems to encourage new growth and prevent flowering, which can diminish the flavor of the leaves.

Don't be afraid to cut it back aggressively – it will bounce back quickly. If you notice it starting to spread beyond its designated area, prune back the runners to keep it contained. As the first frost approaches around mid- October, you can cut back the remaining stems to the ground. Mint is hardy and will return in the spring.

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 starts to flower, as the leaves are most flavorful then. However, you can harvest leaves and stems anytime you need them.

To harvest, simply cut off stems a few inches above the ground. This encourages new growth and keeps the plant productive. Pinch off any flower buds you see to encourage continued leaf production. Mint doesn't ripen off the vine, so harvest only what you need.

As the first frost approaches in mid- October, harvest as much mint as you can and preserve it by drying or freezing. That way, you can enjoy the taste of summer throughout the long Plains winter.

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

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 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 in drought stress. *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 in unexpected places throughout your garden. *What causes it:* Underground runners that spread rapidly and aggressively. *How to fix/prevent it:* Plant in containers. Sink containers into the ground to add a more natural look. Monitor regularly and remove 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. Reduces plant vigor. *What causes it:* Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it (unlike most fungi). *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.

Great Plains Specific Challenges: The hot summer heat and variable rainfall in the Great Plains can stress mint plants, making them more susceptible to pests and diseases. Drought conditions can encourage spider mites, while periods of high humidity can favor fungal diseases like rust and powdery mildew. Consistent watering and good air circulation are key to keeping your mint healthy. Wind protection is also essential to prevent damage to the leaves and stems.

Mint is a great companion plant for tomatoes and peppers. Its strong scent can help deter pests like aphids and flea beetles that often plague these crops in the Plains. Cabbage and broccoli also benefit from mint's pest-repelling properties.

Avoid planting mint near parsley or chamomile. Parsley and mint compete for the same nutrients in the soil. Chamomile is thought to inhibit mint growth. Creating the best possible environment will ensure good production in the growing season.