Mustard Greens in Zone 5B — Great Plains

Mustard greens bring a delightful peppery kick to your salads and stir-fries, and they're surprisingly easy to grow here in the Plains. Plus, a quick harvest of greens is a real morale booster in spring and fall, when other crops are just getting started or winding down.

Sure, our extreme weather and variable rainfall can be a challenge, but with a little planning, you can enjoy fresh mustard greens throughout much of our 178-day growing season. Careful timing and attention to watering are your best friends in this climate.

Starting mustard greens indoors is definitely an option, especially if you're itching to get a head start in early spring. You can sow seeds indoors from early to late March, giving them about 3 weeks before transplanting.

Use seed trays with a good seed-starting mix and keep them warm and well-lit – a simple shop light works wonders. Don't forget to water from the bottom to encourage strong root growth. Keep in mind that our spring weather can be unpredictable, so starting indoors is a good way to hedge your bets against a late cold snap.

Transplant your mustard greens seedlings outdoors from early April through mid May. Just be sure to harden them off first by gradually exposing them to outdoor conditions for about a week.

Space them about 6-12 inches apart in well-drained soil. Keep an eye on the forecast, since we can still get some surprise frosts in early April. Wind protection is essential for young seedlings.

Direct sowing mustard greens is a straightforward method that works well in the Plains. Sow seeds from late March through mid August, aiming for a time when the soil has warmed up a bit.

Prepare the soil by loosening it and removing any rocks or debris. Sow seeds about ½ inch deep and 6-12 inches apart. Direct sowing bypasses the transplant shock, but you'll need to stay on top of watering, especially if we're in a dry spell.

Watering is absolutely crucial for mustard greens in our variable Plains climate. They need consistent moisture to thrive, and drought stress will make them bolt and the leaves turn bitter.

In spring and fall, when temperatures are cooler and rainfall is more frequent, you might only need to water once or twice a week. In the heat of summer, though, you'll likely need to water every day or two, especially if it's windy. 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.

Water at the base of the plants to avoid wetting the leaves, since our low-to-moderate humidity can still lead to fungal issues if the leaves stay wet for too long. Yellowing leaves can indicate overwatering, while wilting and bitterness suggest underwatering. A good layer of mulch will help retain moisture and keep the soil cool during the hot summer months.

You can expect your first harvest of mustard greens from early May through late October, about 45 days after planting. Young leaves will have a milder flavor, while larger leaves will be spicier.

Harvest the outer leaves as needed, leaving the inner leaves to continue growing. This cut-and-come-again approach will give you a continuous supply of greens throughout the season. Be sure to harvest before the plants start to flower, as this will make the leaves bitter.

As the first frost approaches in mid- October, harvest as much as you can. You can also try covering the plants with a frost blanket to extend the harvest a bit longer.

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. The damage is worst on young seedlings.
• 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: Use row covers to protect seedlings. Delay planting until plants are larger. A coating of kaolin clay can help. You can also try neem oil spray. 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. You might also see sticky honeydew residue and curled or distorted new growth.
• What causes it: These are rapid-reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may farm them for honeydew.
• How to fix/prevent it: A strong water spray can knock them off. Encourage ladybugs and lacewings (natural predators). Use insecticidal soap for heavy infestations. Neem oil also works. Avoid excess nitrogen fertilizer, as it attracts them.

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. You'll see irregular holes chewed in the leaves and dark green droppings. White butterflies hovering around plants are a telltale sign.
• What causes it: These are the larvae of white cabbage butterflies. They have multiple generations per season in warm climates.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick the 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 when temperatures rise. The leaves become tough and bitter, and the harvest quality declines.
• What causes it: This happens when a cool-season crop experiences extended warm temperatures. Mustard greens bolt when days consistently exceed 80°F.
• How to fix/prevent it: Time your plantings for cool weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep the soil cool. Harvest before bolting progresses too far.

Great Plains Specific Challenges: Our hot summers and variable rainfall mean that bolting and pest pressure can be significant issues. Consistent watering and careful timing of plantings are crucial for success. Wind protection is also essential, especially for young plants.

Good companions for mustard greens include onions and garlic, as their strong scent can help deter pests. Beets also make good companions, as they don't compete for the same nutrients. Dill attracts beneficial insects that prey on aphids. Lettuce provides ground cover and helps retain moisture.

Avoid planting mustard greens near strawberries or tomatoes. Strawberries are susceptible to some of the same pests as mustard greens, and tomatoes can stunt the growth of mustard greens.