Mustard Greens in Zone 5A — Mountain West

Mustard greens pack a peppery punch that brightens up any meal, and they're surprisingly easy to grow in our Mountain climate. The cool nights even in summer enhance their flavor, making them a fantastic addition to salads, stir-fries, or even a quick sauté. Plus, their quick growth cycle means you can get multiple harvests in our short season.

High altitude gardening presents unique challenges, from intense sun to unpredictable weather. But with a little planning, you can definitely enjoy a bountiful harvest of mustard greens. Our 138-day growing season is just right for these greens, especially if you take advantage of both spring and fall planting windows.

Starting mustard greens indoors is an option, especially if you're aiming for an extra-early spring harvest. Begin in late March through mid April, about three weeks before you plan to transplant. This gives you a head start, considering how late spring can be here.

Use seed trays with a good seed-starting mix. Keep them in a warm spot, around 70°F, and provide plenty of light – a grow light works best. Bottom watering helps prevent damping off and keeps the seedlings evenly moist.

Transplant your mustard greens seedlings outdoors in late April through early June, once the danger of hard frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense sun and cooler nights.

Space the seedlings 6-12 inches apart in well-drained soil. Keep an eye on the weather forecast – a late frost can still happen, so be ready to cover them if needed.

Direct sowing is a great way to grow mustard greens here in the Mountain West, and honestly, it's my preferred method. Sow seeds mid April through late July for a continuous harvest. Direct sowing avoids transplant shock, and mustard greens germinate quickly in cool soil.

Prepare the soil by loosening it and adding some compost. Sow seeds about ½ inch deep and space them 6-12 inches apart. Keep the soil consistently moist until germination, which usually takes about a week.

Consistent moisture is key to happy mustard greens, especially in our dry Mountain climate. While our moderate summer heat isn't as intense as other regions, the low humidity and dry rainfall mean you need to be diligent about watering. Aim to keep the soil consistently moist but not waterlogged.

During the spring and fall, when temperatures are cooler, you might only need to water once or twice a week. In the peak of summer, increase watering to every other day or even daily, depending on rainfall. Stick your finger about 2 inches deep into the soil – if it feels dry, it's time to water.

Generally, aim for about 1 inch of water per week, either from rainfall or irrigation. Water at the base of the plants to avoid wetting the leaves, which can increase the risk of fungal diseases, though our low humidity minimizes this risk. Signs of underwatering include wilting leaves and a bitter taste. Overwatering can lead to yellowing leaves and root rot.

A layer of mulch, like straw or wood chips, can help retain moisture and keep the soil cool, which is especially helpful during the warmer months.

You can expect your first harvest of mustard greens in late May through early October, about 45 days after planting. The best time to harvest is when the leaves are young and tender, usually around 4-6 inches long. These younger leaves have a milder flavor.

Larger leaves will be spicier, but still perfectly edible. Avoid harvesting after the plant starts to bolt (send up a flower stalk), as the leaves will become tough and bitter. To harvest, simply snip off the outer leaves with scissors or a knife, leaving the inner leaves to continue growing.

This cut-and-come-again method allows for continuous production throughout the season. As late September approaches and our first frost looms, harvest any remaining leaves to enjoy one last meal.

What it looks like: Tiny round holes (shot-hole pattern) in the leaves, especially on young seedlings. You might also see small, dark beetles that jump when disturbed. What causes it: Flea beetles are attracted to brassicas and are most damaging to small, young plants. Our intense sun can stress young seedlings, making them more susceptible. How to fix/prevent it: Row covers are your best defense for protecting seedlings. Delay planting until plants are larger and more resilient. Kaolin clay coating can also deter them. Neem oil spray is effective, and interplanting with basil or catnip can help.

What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth. What causes it: Aphids thrive in warm weather and can rapidly reproduce. They're attracted to plants with excess nitrogen. How to fix/prevent it: A strong spray of water can knock them off. Encourage natural predators like ladybugs and lacewings. Insecticidal soap works well for heavy infestations, and neem oil is a systemic option. Avoid over-fertilizing with nitrogen.

What it looks like: Smooth green caterpillars on brassica leaves, with irregular holes chewed in the leaves. You might also see dark green droppings and white butterflies fluttering around. What causes it: These are the larvae of white cabbage butterflies. They can go through multiple generations in a season. How to fix/prevent it: Bt spray is very effective against cabbage worms. Use floating row covers to prevent butterflies from laying eggs. Handpick caterpillars when you see them. Interplant with aromatic herbs like thyme or sage to deter the butterflies.

What it looks like: The plant sends up a flower stalk, and the leaves become tough and bitter. What causes it: Mustard greens are cool-season crops that bolt when temperatures rise consistently above 80°F. How to fix/prevent it: Time your plantings for cool weather – spring and fall are ideal. Choose bolt-resistant varieties. Provide shade during warm spells with shade cloth. Mulch to keep the soil cool. Harvest leaves before bolting progresses too far.

Mountain West Specific Challenges: Our high altitude and intense UV can exacerbate the effects of heat stress on mustard greens, making them more prone to bolting. The dry air and alkaline soil can also stress plants, making them more susceptible to pests. Consistent watering and soil amendments are key to keeping your plants healthy and productive.

Mustard greens benefit from companion planting, especially in our Mountain environment. Onions and garlic are great companions because their strong scent repels many pests that bother mustard greens. Beets are also beneficial, as they improve soil structure and nutrient availability. Dill attracts beneficial insects that prey on pests like aphids. Lettuce provides ground cover, helping to retain moisture in our dry climate.

Avoid planting mustard greens near strawberries or tomatoes. Strawberries are susceptible to some of the same fungal diseases as mustard greens, and tomatoes can compete for nutrients in the soil.