Mustard Greens in Zone 6B — Great Plains

Mustard greens bring a delightful peppery kick to your table, and they’re surprisingly easy to grow here on the Plains. Their quick growth makes them a rewarding crop, even with our variable weather, and they’re delicious steamed, stir-fried, or added to salads for a zing.

While we Plains gardeners face challenges like extreme temperature swings and the risk of hail, mustard greens are a cool-season crop that fits well into our 198-day growing season. Careful timing helps you avoid the worst of the summer heat and ensures a bountiful harvest.

Starting mustard greens indoors is definitely an option, especially if you're aiming for a very early spring harvest. Begin your seeds indoors from late February through mid March, roughly three weeks before you plan to transplant them outside.

Use seed trays filled with a good seed-starting mix and keep them in a warm spot with plenty of light—a sunny windowsill or under grow lights works well. Bottom watering helps prevent damping-off, a common problem with seedlings. Keep in mind that our unpredictable spring weather can make early transplanting tricky, so watch the forecast closely.

Transplanting mustard greens seedlings outdoors should occur from late March through early May. Before transplanting, be sure to harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space the seedlings 6-12 inches apart in well-drained soil. Keep an eye out for late frosts, a common occurrence in the Plains, and be ready to cover your young plants if temperatures dip unexpectedly.

Direct sowing mustard greens is a straightforward and often preferred method, especially for later crops. Sow seeds directly into the garden from mid March through late August.

Prepare the soil by loosening it and removing any rocks or debris. Plant seeds about ½ inch deep, spacing them 6-12 inches apart. Keep the soil consistently moist until germination, which usually takes about a week. Direct sowing is great because it avoids transplant shock, but you'll need to be diligent about thinning seedlings to the correct spacing.

Maintaining consistent moisture is key to growing happy mustard greens here on the Plains. While they aren't drought-tolerant, understanding our climate's quirks will guide your watering.

In the spring and fall, when temperatures are milder and rainfall is more likely, aim for about 1 inch of water per week, either from rain or irrigation. During the hotter summer months, you might need to increase that to 1.5-2 inches per week, especially if we're experiencing a dry spell. Stick your finger about 2 inches deep 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 encourage fungal diseases in our sometimes humid conditions. Signs of underwatering include wilting leaves and slow growth, while overwatering can lead to yellowing leaves and root rot. A layer of mulch, like straw or shredded leaves, can help retain soil moisture and regulate soil temperature, a big plus with our extreme temperature swings.

You can expect your first harvest of mustard greens from late April through early November, about 45 days after planting. The timing will depend on when you sowed your seeds.

Harvest young leaves for a milder flavor, while larger, more mature leaves will have a spicier kick. Pick leaves from the outer part of the plant, leaving the center to continue growing. Mustard greens are a cut-and-come-again crop, so you can harvest continuously throughout the season.

As our first frost approaches in late October, harvest any remaining leaves to enjoy before the cold weather sets in. You may even get a late flush of growth if you protect them from the first few light frosts.

Here are some common problems you might encounter with mustard greens in the Great Plains:

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're most damaging to small, young plants.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger and more resilient. Spray with kaolin clay or neem oil. 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. Ant colonies may "farm" them for honeydew.
• How to fix/prevent it: Knock them off with a strong water spray. Encourage ladybugs and lacewings (natural predators). Use insecticidal soap for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer, which 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. Multiple generations per season in warmer parts of the Plains.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs like thyme or sage. Encourage parasitic wasps.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk. 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.
• 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.

Great Plains Specific Challenges: Our hot summers and variable rainfall can stress mustard greens, making them more susceptible to bolting and pest infestations. Consistent watering, especially during dry spells, and choosing the right planting times are crucial for success. Wind protection is also essential to prevent damage to the leaves.

Companion planting can give your mustard greens a boost here on the Plains. Plant onions and garlic nearby to help deter pests like aphids. Beets are also good companions, as they don't compete for the same nutrients and can help loosen the soil. Dill attracts beneficial insects that prey on cabbage worms. Lettuce can provide ground cover, helping to keep the soil cool and moist.

Avoid planting mustard greens near strawberries, as they are susceptible to similar fungal diseases. Tomatoes can also be poor companions, as they compete for nutrients and attract some of the same pests.