Mustard Greens in Zone 6A — Great Plains

Mustard greens bring a delightful peppery zing to salads, stir-fries, and braised dishes. They’re quick to mature, offering a rewarding harvest even with our variable Plains springs. Plus, their semi-hardy nature allows for both spring and fall crops, extending your fresh greens season.

Our region throws some curveballs with its extreme temperature swings and potential for hail, but mustard greens are surprisingly resilient when timed right. With a growing season that stretches around 188 days, you'll find ample opportunity to enjoy these flavorful greens.

Starting mustard greens indoors gives you a head start, especially if you're aiming for an early spring harvest. Sow seeds indoors from early to late March, about 3 weeks before you plan to transplant. Use seed trays with a good seed-starting mix, provide warmth (around 70°F), and ensure ample light—a simple shop light works wonders.

Bottom watering is key to prevent damping off, especially in our sometimes unpredictable spring weather. Place the tray in a shallow pan of water and let the soil soak it up from the bottom. This encourages strong root growth and avoids wetting the foliage.

Transplant your mustard greens seedlings outdoors from early April through mid May, after they've developed a few sets of true leaves. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense sunshine and wind we often experience.

Space the seedlings 6-12 inches apart, giving them room to grow into full rosettes. Keep an eye on the forecast around transplant time; a late frost can still happen, so be ready to cover your seedlings if needed.

Direct sowing is a simple and effective way to grow mustard greens, especially for a continuous harvest. Sow seeds directly into the garden from mid March through late August. This gives you a long window for multiple plantings.

Prepare the soil by loosening it and adding compost. Mustard greens prefer a soil temperature between 60-75°F for optimal germination. Sow seeds ½ inch deep and space them 6-12 inches apart. Thin the seedlings as they grow to ensure proper spacing. Direct sowing is great, but keep in mind that young seedlings are vulnerable to flea beetles, so monitor them closely.

Mustard greens need consistent moisture to thrive, but they don't like soggy conditions. In our Plains climate, with its variable rainfall and hot summers, watering requires attention. A good rule of thumb is to water deeply once or twice a week, providing about 1 inch of water each time, depending on rainfall.

Use the "finger test" to gauge soil moisture. 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 foliage, which can encourage fungal diseases, especially when humidity creeps up.

During the heat of summer, monitor your plants closely. Drought stress can cause the leaves to become overly spicy and trigger bolting. Mulch around the plants with straw or wood chips to help retain moisture and keep the soil cool. Signs of underwatering include wilting leaves and slow growth, while yellowing leaves and standing water indicate overwatering.

You can expect your first harvest of mustard greens from early May through late October, about 45 days after planting. Young leaves have a milder flavor, while larger, more mature leaves pack a spicier punch. Harvest leaves when they are 4-6 inches long for the best taste and texture.

To harvest, simply snip off the outer leaves, leaving the inner leaves to continue growing. This allows for continuous harvesting throughout the season. Avoid harvesting after the plant starts to flower, as the leaves will become bitter.

As the first frost approaches in mid- October, harvest any remaining leaves to enjoy before the cold weather sets in. You can also cover the plants with a frost blanket to extend the harvest for a few more weeks.

Here are some common problems you might encounter growing 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: These small jumping beetles feed on the leaves. They thrive in warm, dry conditions, which we often get in the Plains.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger and more resilient. You can also try coating the leaves with kaolin clay or spraying with neem oil. Interplanting with basil or catnip can help deter them.

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: Rapidly reproducing sap-sucking insects. Our warm summers can lead to rapid population explosions.
• How to fix/prevent it: Knock them off with a strong spray of water. Encourage natural predators like ladybugs and lacewings. Use insecticidal soap for heavy infestations or neem oil for a systemic approach. Avoid over-fertilizing with nitrogen, as this attracts aphids.

Cabbage Worms

• What it looks like: Smooth green caterpillars on the leaves, with irregular holes chewed in them. You might also see dark green droppings and white butterflies hovering around your plants.
• What causes it: These are the larvae of white cabbage butterflies. They can have multiple generations per season in our warm climate.
• How to fix/prevent it: Bt spray is very effective. Use floating row covers to prevent the butterflies from laying eggs. Handpick the caterpillars. Interplant with aromatic herbs like thyme or sage to deter them, and 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: Mustard greens are a cool-season crop, and they bolt when temperatures rise. Extended warm temperatures above 80°F will trigger bolting.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells, and mulch to keep the soil cool. Harvest leaves before bolting progresses too far.

Great Plains Specific Challenges: The hot heat, low-to-moderate humidity, and variable rainfall in the Great Plains make it crucial to monitor your mustard greens closely. Heat stress can lead to bolting and increased pest pressure. Consistent watering is essential to prevent drought stress, but good drainage is also important to avoid root rot. Be prepared for sudden temperature swings and potential hail, which can damage the leaves.

Companion planting can help your mustard greens thrive. Plant mustard greens near onions and garlic, as their pungent scent deters many pests. 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 aphids and cabbage worms. Lettuce provides ground cover, helping to keep the soil cool and moist.

Avoid planting mustard greens near strawberries or tomatoes. Strawberries are susceptible to some of the same pests as mustard greens, increasing the risk of infestation. Tomatoes can stunt the growth of mustard greens, as they both require similar nutrients and space.