Mustard Greens in Zone 6A — Mountain West

Mustard greens bring a peppery zing to your Mountain West garden, adding fresh flavor to salads and stir-fries. They're a fast-growing crop, perfect for our short season, and the cool nights even in summer enhance their taste. Plus, they thrive in our intense sunlight, packing a nutritional punch.

Our high altitude and short 153-day growing season can be challenging, but with careful timing, you can enjoy a bountiful harvest of mustard greens. The key is to work *with* our Mountain climate, planting at the right time to avoid the worst of the heat and make the most of our intense sunlight.

Starting mustard greens indoors is an option, but direct sowing is generally preferred in our region because they germinate so readily. If you want a head start, especially for an early spring crop, start seeds indoors mid-March through early April, about 3 weeks before you plan to transplant. Use seed trays and provide warmth and bright light.

Bottom watering is essential to prevent damping-off, a fungal disease that can plague seedlings. Just set the tray in a shallow dish of water and let the soil absorb it from the bottom. Remember that our spring weather can be unpredictable, so be prepared to protect your seedlings from late frosts.

Transplant your mustard greens outdoors mid-April through late May. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense sun and cooler temperatures of our Mountain climate.

Space your transplants 6-12 inches apart. Be mindful of potential late frosts – have row covers ready to protect your young plants if temperatures dip. Our high altitude means the sun is intense, so choose a spot that gets some afternoon shade to prevent scorching.

Direct sowing mustard greens is easy and effective in our region. Sow seeds early April through early August for succession planting. Prepare your soil by loosening it and adding compost. Mustard greens aren't too picky, but they appreciate well-drained soil.

Sow seeds 1/4 inch deep and space them 6-12 inches apart. Keep the soil consistently moist until germination. Direct sowing avoids transplant shock and allows the plants to establish strong root systems. Plus, you can easily plant multiple successions for a continuous harvest.

Maintaining consistent soil moisture is crucial for healthy mustard greens in our dry Mountain climate. Aim to keep the soil consistently moist, but not waterlogged. Letting the soil dry out too much can cause the leaves to become overly spicy and trigger bolting.

During the spring and fall, when temperatures are cooler, water deeply once or twice a week, providing about 1 inch of water each time. In the warmer summer months, you may need to water every other day, especially if we're experiencing a dry spell. Use the finger test: stick your finger into the soil about 2 inches deep. If it feels dry, it's time to water.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases, even though our humidity is low. Signs of underwatering include wilting leaves, while yellowing leaves can indicate overwatering. A layer of mulch, like straw or wood chips, helps retain moisture and keep the soil cool, which is especially beneficial during our hot summer days.

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

To harvest, simply snip off the outer leaves, 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 (bolt), as this will make the leaves bitter.

As the first frost approaches in early October, harvest any remaining leaves. You can also cover the plants with a frost blanket to extend the harvest a bit longer, but mustard greens are semi-hardy, not fully hardy. Even after a light frost, you might still be able to salvage some leaves.

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, especially on young seedlings. You might see small, dark beetles jumping when disturbed.
• What causes it: These small jumping beetles love to feed on brassicas. They're most damaging to small, young plants that are already stressed by our intense sun and alkaline soil.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until plants are larger and more resilient. A kaolin clay coating can deter them. Neem oil spray can also help. Interplanting with basil or catnip can confuse the beetles. Healthy, vigorous plants can often outgrow the damage.

Aphids

• What it looks like: Clusters of tiny soft-bodied insects (green, black, or white) on stems and leaf undersides. You might also see sticky honeydew residue or curled, distorted new growth.
• What causes it: These sap-sucking insects reproduce rapidly, especially when plants are stressed. In our Mountain climate, they can thrive despite the low humidity, especially if plants are getting too much nitrogen.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage natural predators like ladybugs and lacewings. Insecticidal soap is effective 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 the leaves, irregular holes chewed in the leaves, and dark green droppings. You might also see white butterflies hovering around your plants.
• What causes it: These are the larvae of white cabbage butterflies. They can go through multiple generations in a season, even in our somewhat cooler climate.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent the butterflies from laying eggs on your plants. Handpick the caterpillars whenever you see them. Interplant with aromatic herbs like thyme or sage to deter the butterflies. Encourage parasitic wasps, which prey on the caterpillars.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk. The leaves become tough and bitter, and the harvest quality declines.
• What causes it: Mustard greens are a cool-season crop, and they bolt when temperatures rise. Extended warm temperatures above 80°F will trigger bolting. This is especially a concern in our Mountain climate, where we can have sudden heat waves.
• How to fix/prevent it: Time your plantings for cool weather in the spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells with shade cloth. Mulch to keep the soil cool. Harvest the leaves before bolting progresses too far.

Mountain West Specific Challenges: Our moderate-at-altitude heat, low humidity, and dry rainfall can create a challenging environment for mustard greens. The intense sun can scorch leaves if they're not properly hardened off. The dry air means you need to be vigilant about watering, and the alkaline soil can affect nutrient availability. Be sure to amend your soil with compost to improve drainage and nutrient uptake.

Good companions for mustard greens in the Mountain West include onions and garlic. Their strong scent can deter pests like aphids and flea beetles, which can be a problem in our region. Beets are also good companions, as they don't compete for the same nutrients and can help loosen the soil.

Dill is another beneficial companion, attracting beneficial insects like ladybugs and lacewings that prey on aphids and other pests. Lettuce can provide shade for mustard greens during the hottest part of the day, which is especially helpful in our intense sun.

Avoid planting mustard greens near strawberries or tomatoes. Strawberries are susceptible to the same fungal diseases, and tomatoes can attract pests that also feed on mustard greens. These combinations can increase the risk of problems in your Mountain garden.