Mustard Greens in Zone 3B — Midwest

Mustard greens bring a peppery zing to salads and stir-fries, and they thrive in our fertile Midwest soil. The fast growth means you can get multiple harvests, even with our shorter growing season. It's rewarding to grow something so flavorful right in your backyard.

Sure, we have our share of Midwest weather challenges – variable springs and summer heat spells, not to mention the occasional tornado. But with a little planning, you can easily fit several plantings of mustard greens into our 118-day growing season. The key is timing!

Starting mustard greens indoors isn't essential, but it can give you a head start, especially if you're eager for an early harvest. If you choose to start indoors, aim for early to late April, about three weeks before you intend to transplant. This helps you get a jump on our moderate-to-late spring.

Use seed trays with a good seed-starting mix, keep them warm, and provide plenty of light – a simple shop light works great. Don't forget to bottom water the trays to encourage strong root growth without damping off.

Transplant your mustard greens seedlings outdoors from early May through mid June, once the danger of a hard frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This prepares them for the shock of the real world.

Space the seedlings 6-12 inches apart in well-drained soil. Keep an eye on the weather forecast around transplant time; a late frost can still sneak in, so be prepared to cover your seedlings if necessary.

Direct sowing mustard greens is a simple and effective method, and honestly, it's my preferred way to go. Sow seeds from late April through mid July for a continuous harvest. The fertile soil of the Midwest provides a great foundation for direct sowing.

Prepare the soil by loosening it and removing any large clumps. Sow seeds about ½ inch deep and space them 6-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Mustard greens need consistent moisture to thrive, but they don't like to be waterlogged, something to keep in mind with our wet summers. Aim to keep the soil consistently moist, but not soggy. Drought stress can make the leaves spicier and cause the plants to bolt prematurely.

During the warmer months, especially during our summer heat spells, check the soil moisture regularly. Stick your finger about two 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 rainfall or irrigation.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our moderate-to-humid climate. Overhead watering is fine, just do it in the morning so the leaves have time to dry out before nightfall.

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, can help retain moisture and keep the soil cool during the summer.

You can expect your first harvest of mustard greens from early June through late September, about 45 days after planting. The key is to harvest them at the right stage for your taste preferences. Younger leaves are milder, while larger leaves have a spicier kick.

Harvest the outer leaves by snipping them off near the base of the plant, leaving the inner leaves to continue growing. This encourages continuous production throughout the season. Avoid harvesting after the plant begins to flower, as the leaves will become bitter.

As our first frost approaches in mid- September, harvest any remaining leaves that are large enough to use. You can also cover the plants with a frost blanket to extend the harvest for a few more weeks, but don't expect them to survive a hard freeze.

Here are some common problems you might encounter growing mustard greens in the Midwest:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves. You might see small dark beetles that jump when disturbed. They do the most damage to young seedlings.
• What causes it: These are small jumping beetles that feed on the leaves. They are especially damaging to small, young plants.
• How to fix/prevent it: Row covers are great for protecting seedlings during their vulnerable stage. You can also delay planting until the plants are larger. Try a kaolin clay coating, or 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. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: These are rapid-reproducing sap-sucking insects. Populations can 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). Insecticidal soap works for heavy infestations, and neem oil works systemically. Avoid excess nitrogen fertilizer, as it attracts them.

Cabbage Worms

• What it looks like: Smooth green caterpillars on the brassica leaves. Irregular holes chewed in the leaves. You may see dark green droppings and white butterflies hovering around the plants.
• What causes it: These are the larvae of white cabbage butterflies. There can be multiple generations per season in our warm climate.
• How to fix/prevent it: Bt spray is very effective. Floating row covers can prevent egg laying. Handpick the caterpillars when you see them. Interplant with aromatic herbs like thyme and sage, and encourage parasitic wasps.

Bolting in Heat

• What it looks like: The cool-season crop sends up a flower stalk when temperatures rise. The leaves become tough and bitter, and harvest quality declines.
• What causes it: Extended warm temperatures above the crop's comfort zone. Brassicas bolt when days consistently exceed 80°F.
• 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, and mulch to keep the soil cool. Harvest before bolting progresses.

Midwest Specific Challenges: Our moderate-to-hot summers and moderate-to-humid humidity can create favorable conditions for pests like aphids and cabbage worms. The wet-summer rainfall can also increase the risk of fungal diseases. Be vigilant about monitoring your plants and take action quickly to prevent problems from escalating.

Good companions for mustard greens include onions and garlic. Their strong scent can deter pests like aphids and flea beetles. 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 pests like cabbage worms. Lettuce provides ground cover, helping to retain moisture and suppress weeds.

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