Mint in Zone 7A — Mountain West

Mint is a fantastic addition to any high-altitude garden. Its refreshing flavor elevates everything from summer drinks to savory dishes, and you’ll find yourself snipping fresh sprigs constantly. Plus, the sheer satisfaction of growing your own herbs in our intense Mountain sun is hard to beat, especially when a cool evening calls for a comforting mint tea.

Our short growing season and alkaline soil can present challenges, but with a little planning, growing mint is absolutely achievable. We have about 173 days between frosts, so timing your planting right ensures a plentiful harvest.

Starting mint from seed indoors is possible, but honestly, it's often easier to get a jumpstart by purchasing established plants or getting a division from a neighbor. If you do want to start from seed, aim for mid-February through early March, about eight weeks before you plan to transplant.

Use seed trays with a good seed-starting mix, and provide consistent warmth (around 70°F) and plenty of light – a grow light works wonders. Bottom watering is key to prevent damping off; simply set the tray in a shallow dish of water and let the soil absorb moisture from the bottom. Remember, our spring weather can be unpredictable, so be patient!

Transplant your mint outdoors from mid-April through mid-May, after the danger of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to our intense UV and fluctuating temperatures.

Space your plants 18-24 inches apart. Mint spreads aggressively, so consider planting it in containers to keep it from taking over your garden. You can also sink a bottomless container into the ground to contain the roots. Given our late spring frosts, keep an eye on the weather and be prepared to cover your young plants if needed. Buying starts or getting divisions from another gardener is the way to go.

Mint thrives in moist soil, which can be a bit of a balancing act in our dry Mountain climate. Aim for consistent moisture, but avoid soggy conditions.

During the peak of summer, when temperatures can reach around 85°F, water deeply about 1-2 inches per week, depending on rainfall. Use the finger test: stick your finger about two inches into the soil. If it feels dry, it's time to water. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our environment, even with low humidity.

Signs of underwatering include wilting leaves and slow growth. 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 in our intense sun.

Pruning mint is essential for controlling its spread and encouraging healthy growth. The great thing about mint is that you can prune it to harvest.

Throughout the growing season, regularly harvest entire stems, cutting them back to just above a leaf node. This encourages bushier growth. Pinch off any flower buds as they appear to keep the plant focused on leaf production. As the first frost approaches in early October, give your mint a final trim. You can either leave it in place to overwinter or dig up some to bring indoors for fresh mint all winter long.

You can expect your first harvest of mint 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.

Simply snip off stems as needed, taking care not to damage the rest of the plant. Regular harvesting encourages continued production. As the first frost approaches in early October, harvest any remaining leaves and stems. You can dry them for later use or make mint-infused oil or vinegar.

Here are some common problems you might encounter with mint in our Mountain West gardens:

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 thrive in warm, humid conditions with moisture on leaves. While our humidity is low, overhead watering or morning dew can create enough moisture for rust to develop.
• How to fix/prevent it: Remove affected leaves immediately. Avoid overhead watering and improve air circulation by spacing plants adequately. Applying sulfur or copper fungicide can help control the spread.

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, which is common in our region.
• How to fix/prevent it: A strong spray of water, daily for a week, is often the best treatment. Increase humidity around plants by misting them. Neem oil or insecticidal soap can also be effective.

Invasive Spreading

• What it looks like: Mint popping up everywhere you don't want it!
• What causes it: Mint's aggressive root system sends out runners that can quickly colonize a large area.
• How to fix/prevent it: Plant mint in containers to contain its spread. You can also sink a bottomless container into the ground. Regularly monitor 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.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it. This can be common in our region with our cool nights and dry days.
• 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) can also be effective.

Mountain West Specific Challenges: The combination of intense sun and low humidity in our Mountain West climate can stress mint plants, making them more susceptible to pests and diseases. Regular watering and mulching can help mitigate these effects. Also, hail is a risk. Protect your plants when hail is in the forecast.

Mint is a great companion plant for tomatoes and peppers. Its strong scent can help repel pests like aphids and cabbage moths that often plague these crops. Mint also benefits cabbage and broccoli by deterring cabbage white butterflies.

Avoid planting mint near parsley and chamomile. Mint can inhibit the growth of parsley. Chamomile prefers drier conditions, while mint prefers moist soil, creating conflicting needs.