Mustard Greens in Zone 4A — Mountain West

Mustard greens are a fantastic addition to the Mountain West garden. Their peppery bite adds zing to salads, stir-fries, and soups, and they thrive in our cool spring and fall weather. Plus, nothing beats the satisfaction of harvesting your own greens just minutes before they hit the table, especially when our short growing season makes every homegrown bite count.

Our high altitude and intense sun can be tough on some crops, but mustard greens are surprisingly adaptable. The short 118-day growing season means timing is key, but with a little planning, you can enjoy a bountiful harvest from early summer well into fall.

Starting mustard greens indoors is an option, but honestly, direct sowing often works just as well here in the Mountain West. However, if you're aiming for a super early harvest or want a head start, start seeds indoors from early to late April, about three weeks before you plan to transplant.

Use seed trays or small pots filled with a good seed-starting mix. Keep them warm and provide plenty of light – a sunny windowsill or grow lights work well. Bottom watering helps prevent damping-off, a common problem with seedlings. Given our late springs, indoor starting can give you a jump on the season if the weather is still unpredictable.

Once the danger of hard frost has passed, usually from early May through mid June, it's time to transplant your mustard greens seedlings outdoors. 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 we often experience.

Plant seedlings 6-12 inches apart in well-drained soil. Be mindful of late-season frosts – keep some row covers handy to protect your young plants if needed. Our unpredictable spring weather can throw curveballs, but mustard greens are pretty resilient.

Direct sowing is a simple and effective way to grow mustard greens in the Mountain West. Sow seeds from late April through mid July for a continuous harvest. Choose a spot with full sun to partial shade, and make sure the soil is loose and well-prepared.

Sow seeds about ¼ inch deep, spacing them 6-12 inches apart. Keep the soil consistently moist until germination. Direct sowing is a great option because mustard greens germinate quickly in cool soil, and you don't have to worry about disturbing their roots during transplanting.

Consistent watering is essential for healthy mustard greens in our dry Mountain West climate. While they aren't drought-tolerant, they also don't like soggy soil. The key is to find the right balance.

In the spring, when temperatures are cooler, you might only need to water once or twice a week, providing about 1 inch of water each time. As summer heats up, especially with our intense sun, increase watering to 2-3 times per week, ensuring the soil stays consistently moist. Use the "finger test" – stick your finger about 2 inches into the soil. If it feels dry, it's time to water.

Water at the base of the plants to avoid wetting the leaves, which can lead to fungal problems, although our low humidity minimizes this risk. Underwatering will cause the leaves to become tough and spicy, and can trigger bolting. Overwatering, on the other hand, can lead to root rot. A layer of mulch, like straw or wood chips, helps retain moisture and regulate soil temperature, especially important during our hot summer days.

You can expect your first harvest of mustard greens about 45 days after planting, typically from early June through late September. The best time to harvest is when the leaves are young and tender for a milder flavor. As the leaves mature, they become spicier.

Harvest by cutting individual leaves from the outer part of the plant, leaving the inner leaves to continue growing. This allows for continuous harvest throughout the season. Be sure to harvest before the plant starts to flower, as bolting will make the leaves bitter.

As our first frost approaches in mid- September, harvest as many leaves as you can. Even if a light frost nips the plants, they might still be salvageable, but it's best to get them while they're good.

Here are some common problems you might encounter with mustard greens in the Mountain West:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves. Small dark beetles that jump when disturbed.
• What causes it: Small jumping beetles that feed on leaves, especially damaging to young seedlings. They thrive in our dry conditions.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger and more resilient. Kaolin clay coating can deter them. Neem oil spray can also help.

Aphids

• What it looks like: Clusters of tiny soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects. Our warm days and cool nights in summer provide ideal conditions for population booms.
• How to fix/prevent it: Strong water spray to knock them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap for heavy infestations. Neem oil works systemically.

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. Irregular holes chewed in leaves. Dark green droppings.
• What causes it: Larvae of white cabbage butterflies. They lay eggs on the underside of leaves, and the caterpillars munch away.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars if you find them.

Bolting in Heat

• What it looks like: Cool-season crop sends up a flower stalk. Leaves become tough and bitter.
• What causes it: Extended warm temperatures. Mustard greens bolt when days consistently exceed 80°F, and our intense sun can exacerbate the problem.
• How to fix/prevent it: Time plantings for cool weather (spring/fall). Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep soil cool. Harvest before bolting progresses.

Mountain West Specific Challenges: The moderate-at-altitude heat and intense UV light can stress mustard greens, making them more susceptible to bolting and insect damage. Our dry climate necessitates consistent watering, but also reduces the risk of fungal diseases. Hail can also damage leaves, so consider using row covers or netting if hail is in the forecast.

Companion planting can really benefit your mustard greens in the Mountain West garden. Onions and garlic are great companions because their strong scent repels many pests that bother mustard greens. Beets are also good neighbors, as they help loosen the soil and improve drainage. Dill attracts beneficial insects like ladybugs, which prey on aphids. Lettuce provides ground cover, helping to keep the soil cool and moist during our hot summer days.

Avoid planting mustard greens near strawberries or tomatoes. Strawberries and mustard greens compete for nutrients, while tomatoes can attract pests that also affect mustard greens.