Mustard Greens in Zone 3B — Great Plains

Mustard greens pack a flavorful punch that brightens up our short Plains growing season. Their peppery bite adds zest to salads and stir-fries, and they're surprisingly cold-tolerant, giving you fresh greens even as the weather cools down. Plus, they thrive in our fertile prairie soil and intense sunshine.

Our region's extreme weather can be a challenge, with temperature swings and the risk of hail. But with a little attention to timing, you can easily fit mustard greens into our 118-day growing season. Let's dive into how to make it happen.

Starting mustard greens indoors is an option, but honestly, they do so well direct sown that it's usually not worth the effort unless you're really itching for an extra-early start. If you do want to get a head start, sow seeds indoors from early to late April, about 3 weeks before you plan to transplant.

Use seed trays with a good seed-starting mix, keep them warm, and provide plenty of light – a simple shop light works wonders. Bottom watering helps prevent damping-off. Remember, spring in the Plains can be variable, so be prepared to adjust your plans if we get a late cold snap.

Transplant your mustard greens seedlings outdoors from early May through mid June, once the risk of hard frost has passed. Before you put them in the ground, harden them off by gradually exposing them to outdoor conditions for about a week.

Plant them 6-12 inches apart in well-drained soil. Keep an eye on the forecast – a late hailstorm can decimate young transplants, so be ready to cover them if needed. Wind protection is essential, especially for young plants.

Direct sowing is the easiest way to grow mustard greens in our region. Sow seeds directly into the garden from late April through mid July. The soil should be at least 50°F for good germination.

Prepare the soil by loosening it and adding some compost. Sow seeds about ½ inch deep and 6-12 inches apart. Keep the soil consistently moist until the seedlings emerge. Direct sowing avoids transplant shock, but young seedlings are more vulnerable to flea beetles.

Watering is crucial for mustard greens, especially in our variable Plains climate. You need to keep the soil consistently moist, but not waterlogged. Drought stress makes the leaves spicier and can trigger bolting, which ruins the flavor.

During the cooler spring months, you might only need to water once or twice a week, depending on rainfall. As the summer heat kicks in, increase watering to every other day or even daily if the soil dries out quickly. Stick your finger about 2 inches deep into the soil – if it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rain or irrigation. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our low-to-moderate humidity.

Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. A layer of mulch, like straw or wood chips, helps retain moisture and regulate soil temperature, which is especially helpful during our hot summers.

You can expect your first harvest of mustard greens from early June through late September, about 45 days after planting. Young leaves are milder and more tender, while larger leaves have a stronger, spicier flavor.

Harvest the outer leaves as needed, leaving the inner leaves to continue growing. This encourages continuous production throughout the season. Pick the leaves before the plant starts to flower (bolt), as bolting makes the leaves bitter.

As our first frost approaches around mid- September, harvest any remaining leaves to enjoy before the cold sets in. Mustard greens can tolerate a light frost, but a hard freeze will damage them.

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. You'll see small, dark beetles that jump when disturbed.
• What causes it: These small jumping beetles feed on the leaves. They're most damaging to small, young plants, especially during dry spells.
• How to fix/prevent it: Row covers are your best bet to protect seedlings. You can also delay planting until plants are larger and more resistant. Kaolin clay coating and neem oil spray can help. Interplant with basil or catnip to 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: These sap-sucking insects reproduce rapidly, especially in warm weather. Ant colonies may farm them for honeydew.
• How to fix/prevent it: A strong water spray knocks them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap works for heavy infestations. 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. You might see white butterflies hovering around plants.
• What causes it: These are the larvae of white cabbage butterflies. They have multiple generations per season.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars when you see them. Interplant with aromatic herbs like thyme or sage.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk. 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.
• How to fix/prevent it: Time your 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, combined with variable rainfall, make consistent watering crucial to prevent bolting and ensure tender leaves. Wind protection is also essential to prevent damage to young plants. Be prepared for extreme temperature swings, which can stress the plants and make them more susceptible to pests and diseases.

Mustard greens benefit from companion planting. Onions and garlic help deter pests with their strong scent. Beets are good neighbors because they don't compete for the same nutrients. Dill attracts beneficial insects that prey on pests. 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 and diseases as mustard greens, and tomatoes can stunt the growth of mustard greens.