Mustard Greens in Zone 6B — Mountain West

Mustard greens thrive in our Mountain West gardens, offering a spicy kick to salads and stir-fries. The cool nights even in summer enhance their flavor, making them a delicious and versatile addition to your kitchen garden. There's real satisfaction in harvesting fresh greens right outside your door.

Our high altitude, intense sun, and short growing season present challenges, but careful timing will get you a great harvest. With a 163-day growing season, you can easily enjoy multiple crops of mustard greens.

Starting mustard greens indoors isn't always necessary, but it can give you a head start, especially if you're itching to get gardening before the ground thaws. Starting seeds indoors from mid-March through early April gives you about a 3-week jump on the season.

Use seed trays with a good seed-starting mix and keep them in a warm spot with plenty of light. A sunny south-facing window works, but grow lights are even better. Remember to bottom water your seedlings to encourage strong root growth. With our late springs, this indoor head start can be valuable.

Transplant your mustard greens seedlings outdoors from mid-April through late May, after the danger of hard frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense UV and cooler nights.

Space your plants 6-12 inches apart in well-drained soil. Keep an eye on the weather forecast – a late spring snow or hail storm can still happen. Be ready to cover your young plants if needed.

Direct sowing mustard greens is a simple and effective method, especially for succession planting. You can direct sow from late March through early August, ensuring a continuous harvest.

Prepare your soil by loosening it and removing any rocks or debris. Mustard greens prefer soil temperatures between 45°F and 75°F for optimal germination. Sow seeds 1/4 inch deep and space them 6-12 inches apart. Thin seedlings as needed. Direct sowing is a great option for our longer days and intense sun.

Mustard greens need consistent moisture to thrive in our dry Mountain West climate. Aim to keep the soil consistently moist, but not waterlogged. These plants are not drought-tolerant, and underwatering leads to spicier leaves and premature bolting.

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, especially with our intense sun, you may need to water every other day, or even daily. The finger test is your friend: stick your finger about 2 inches into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, adjusting based on rainfall.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases. While our low humidity reduces this risk, it's still a good practice. Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. Mulching around your plants with straw or wood chips helps retain moisture and regulate soil temperature, which is especially helpful in our variable climate.

You can expect your first harvest of mustard greens around mid-May if you start early indoors, and continuously through mid-October from direct sowings. Mustard greens are ready to harvest about 45 days after planting.

Harvest young leaves when they are about 4-6 inches long for a milder flavor. Larger leaves will be spicier. Pick individual leaves from the outside of the plant, leaving the center to continue growing. This encourages continuous production throughout the season. Be sure to harvest before the plant starts to flower, as bolting will make the leaves bitter.

As the first frost approaches in early October, harvest any remaining leaves to enjoy one last meal. You might also consider covering your plants with a frost blanket to extend the harvest a bit longer.

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

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves, especially on young seedlings. You might see small dark beetles jumping when disturbed.
• What causes it: Small jumping beetles that feed on leaves. They are most damaging to small, young plants and thrive in our dry conditions.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until plants are larger and more resilient. Kaolin clay coating can deter them. Neem oil spray can also help. Interplant with basil or catnip. Healthy, vigorous plants often outgrow the damage.

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. Populations explode in warm weather.
• How to fix/prevent it: A strong water spray knocks them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap works for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer, as it attracts them.

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. Irregular holes chewed in leaves. Dark green droppings. White butterflies hovering around plants.
• What causes it: Larvae of white cabbage butterflies.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs like thyme and sage. Encourage parasitic wasps.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk, and the leaves become tough and bitter.
• What causes it: Extended warm temperatures above the crop's comfort zone. Mustard greens bolt when days consistently exceed 80°F. Our intense sun can exacerbate this.
• How to fix/prevent it: Time plantings for cool weather (spring/fall). Choose bolt-resistant varieties. Provide shade during warm spells with shade cloth. Mulch to keep soil cool. Harvest before bolting progresses.

Mountain West Specific Challenges: Our combination of moderate-at-altitude heat, intense UV, low humidity, and dry rainfall can stress mustard greens. Consistent watering is crucial to prevent bolting and maintain leaf quality. Row covers and shade cloth can help moderate temperature and protect from pests.

Companion planting can boost the health and productivity of your mustard greens.

Good companions include onions and garlic, whose strong scent deters pests like aphids and cabbage worms. Beets also make good neighbors, as they don't compete for the same nutrients and can help loosen the soil. Dill attracts beneficial insects that prey on common garden pests. Lettuce provides ground cover, helping to retain moisture in our dry climate and suppress weeds.

Avoid planting mustard greens near strawberries, as they can be susceptible to similar fungal diseases. Tomatoes can also hinder mustard green growth, possibly due to allelopathic effects (releasing chemicals that inhibit the growth of other plants).