Mint in Zone 9B — Desert Southwest

Mint is a fantastic addition to any Desert Southwest garden. Its refreshing flavor elevates everything from iced tea to summer salads, and it's incredibly satisfying to snip fresh herbs from your own backyard, even in our arid climate. Plus, it thrives in containers, making it perfect for small spaces or controlling its spread.

While the extreme heat and intense sun of our Desert Southwest summers can be challenging, starting mint at the right time gives it a head start. With our long, 313-day growing season, you'll be enjoying fresh mint for months with proper planning.

Starting mint seeds indoors isn't strictly necessary in our climate, especially since we have two distinct growing seasons. However, if you want a jump start, it's definitely doable.

Begin in early to late December, giving the seedlings about 8 weeks indoors before transplanting. Use seed trays with a good seed-starting mix, providing warmth and bright light – a grow light works wonders. Water from the bottom to encourage strong root growth; set the tray in a shallow dish of water until the surface looks moist. Given our very-early spring character, this head start can get you harvesting even sooner.

You can transplant your mint seedlings, or divisions from a friend, outdoors from early February through early March. Before planting, harden off the seedlings by gradually exposing them to outdoor conditions for about a week.

Space plants 18-24 inches apart, or better yet, plant them in containers. Mint is notorious for spreading, and a container helps keep it in check. Keep an eye on the weather; even though it's mild, protect young transplants from any late frosts.

Mint loves moisture, a bit of a contrast to many desert-adapted plants, so watering is crucial, especially during our extreme summer heat. While it can tolerate some shade, it doesn't tolerate drying out!

During the cooler spring and fall months, water deeply about once a week, providing about 1 inch of water. In the heat of summer, increase this to 2-3 times per week, or whenever the top two inches of soil feel dry to the touch ("the finger test"). Water at the base of the plant to avoid wetting the leaves, which can invite fungal problems, especially with our monsoon moisture. Signs of underwatering include wilting and yellowing leaves, while overwatering can lead to root rot. A layer of mulch, such as shredded bark or straw, helps retain moisture and regulate soil temperature.

Pruning mint is less about shaping and more about controlling its aggressive growth and encouraging fresh foliage. Throughout the growing season, harvest entire stems regularly, cutting them back to just above a leaf node.

This encourages bushier growth and prevents the plant from flowering, which can diminish the flavor of the leaves. As first frost approaches in mid- December, cut the plant back significantly to prepare it for winter dormancy.

You can expect your first harvest of mint from early April through late May, about 60 days after planting. The leaves are most flavorful before the plant flowers, so harvest frequently to encourage continued leaf production.

Simply snip off stems as needed, using sharp scissors or pruners. Pinch off any flower buds you see to keep the plant focused on producing leaves. As the season winds down and first frost approaches in mid- December, harvest any remaining leaves and dry or freeze them for later use.

Here are some common problems you might encounter with mint in the Desert Southwest:

• 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: Rust fungi thrive in warm, humid conditions. Our monsoon season can create these conditions, even briefly.
• How to fix/prevent it: Remove affected leaves promptly. Improve air circulation by spacing plants adequately. Avoid overhead watering, and consider applying a sulfur or copper fungicide if the problem persists.
• 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: These tiny arachnids thrive in hot, dry conditions – basically, our entire summer!
• How to fix/prevent it: A strong spray of water, daily for a week, is often the best treatment. Increase humidity around plants (difficult, but possible with grouping). 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: Underground runners that spread aggressively.
• How to fix/prevent it: Plant in containers! Seriously, that's the best way. Otherwise, be vigilant about pulling up unwanted shoots.
• 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: Fungi that thrive in warm days, cool nights, and moderate humidity.
• How to fix/prevent it: Improve air circulation through spacing and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays can help.

Desert Southwest Specific Challenges: The extreme heat and intense sun can stress mint, making it more susceptible to pests and diseases. Consistent watering is crucial to combat the arid humidity, but avoid overhead watering to prevent fungal issues during the monsoon season.

Mint makes a great companion plant for tomatoes and peppers, helping to deter pests like aphids and flea beetles. It also benefits cabbage and broccoli by repelling cabbage moths.

Avoid planting mint near parsley or chamomile, as it can inhibit their growth. Mint's strong scent can overwhelm these more delicate herbs, especially in our compact desert gardens.