Mint in Zone 3B — Mountain West

Mint is a fantastic addition to any Mountain West garden. Its refreshing flavor elevates everything from summer drinks to savory dishes, and the invigorating scent is a welcome presence in our dry air. Plus, the satisfaction of growing your own herbs in our challenging climate is hard to beat!

Our high altitude, intense sun, and short 108-day growing season can make gardening tricky. But with careful timing and a little extra attention, you can absolutely enjoy a thriving mint patch.

Starting mint from seed indoors is an option, but honestly, in our short season, it's often easier to buy starts from a local nursery or get a division from a friend. If you're determined to start from seed, begin in late March through mid April, about 8 weeks before you plan to transplant.

Use seed trays with a good seed-starting mix and provide warmth (a heat mat helps) and plenty of light (grow lights are best). Be sure to water from the bottom to avoid damping off. Remember, our late springs mean you need to be patient!

Transplant your mint outdoors in late May through late June, once the danger of frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space plants 18-24 inches apart. Mint is an aggressive spreader, so consider planting it in containers to keep it from taking over your garden. Weather in late May can be unpredictable, so watch out for late frosts and protect your young plants if necessary.

Mint loves moist soil, which can be a bit of a challenge in our dry Mountain West climate. During the peak of summer, especially when we're getting those intense UV rays, you'll likely need to water your mint deeply a couple of times a week.

Stick your finger about two inches into the soil – if it feels dry, it's time to water. Aim for about an inch of water per week, adjusting based on rainfall. Water at the base of the plant to avoid getting the leaves wet, which can encourage fungal diseases in our cool nights.

Watch for signs of underwatering, like wilting leaves, or overwatering, like yellowing leaves. A layer of mulch around your mint plants will help retain moisture and keep the soil cool during those hot summer days.

Pruning mint is essential, especially if you want to keep it from taking over your entire garden. Throughout the growing season, regularly harvest entire stems to encourage new growth and prevent flowering.

Don't be afraid to cut it back aggressively – mint thrives on it! As the first frost approaches in early September, give your mint one last hard pruning. This will help it conserve energy over the winter and be ready to bounce back next spring.

You can expect your first mint harvest in late July through mid September, about 60 days after transplanting. The leaves are most flavorful before the plant starts to flower, so keep an eye out for flower buds and pinch them off to encourage continued leaf production.

To harvest, simply snip off stems with scissors or pruning shears. Regular harvesting will keep your mint plant productive throughout the season. As the first frost approaches in early September, harvest as much mint as you can and preserve it by drying or freezing for use throughout the winter.

Mint is generally easy to grow, but here are a few common problems you might encounter in the Mountain West:

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:* Rust fungi thrive in warm, humid conditions with moisture on leaves. *How to fix/prevent it:* Remove affected leaves immediately. Avoid overhead watering, and ensure good air circulation around your plants. A sulfur or copper fungicide can help.

Spider Mites *What it looks like:* Fine stippling (tiny white dots) on leaves, fine webbing on the leaf undersides and between stems. Leaves turn bronze or yellow. *What causes it:* These tiny arachnids thrive in hot, dry conditions, and their populations explode when plants are drought-stressed. *How to fix/prevent it:* A strong spray of water (daily for a week) is often the best treatment. Increase humidity around your plants. Neem oil or insecticidal soap can also help.

Invasive Spreading *What it looks like:* Mint popping up everywhere you don't want it! *What causes it:* Mint spreads rapidly through underground runners. *How to fix/prevent it:* Plant mint in containers to restrict its spread. If you plant it in the ground, consider burying a barrier around the planting area.

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. *How to fix/prevent it:* Improve air circulation by spacing plants properly and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays can help.

Mountain West Specific Challenges: Our low humidity can actually help prevent some fungal diseases on mint, but spider mites can be a real problem during dry spells. The intense sun can also stress plants, so providing some afternoon shade can be beneficial, especially for container-grown mint.

Mint is a great companion plant for tomatoes and peppers, as its strong scent can help repel pests like aphids and cabbage moths. It also benefits cabbage and broccoli by deterring cabbage white butterflies.

Avoid planting mint near parsley and chamomile. Mint's aggressive growth can overwhelm these more delicate herbs, and it can also affect the flavor of chamomile.