Mustard Greens in Zone 3A — Mountain West

Mustard greens are a fantastic addition to any Mountain West garden. Their peppery flavor adds a kick to salads and stir-fries, and they're incredibly versatile – you can even sauté them. Plus, few things beat the satisfaction of harvesting your own greens during our short, intense growing season.

Our high altitude, intense sun, and short growing season can be a challenge, but mustard greens are quick to mature, making them a manageable and rewarding crop. With a 96-day growing season, careful timing ensures you can harvest plenty before the first frosts arrive.

Starting mustard greens indoors in our climate can be useful, but it's not always necessary. Given our short season, it can give you a head start. If you want to try it, start seeds indoors from mid April through mid May, about three weeks before you plan to transplant.

Use seed trays filled with a good seed-starting mix. Keep them consistently moist by bottom watering to avoid disturbing the seeds. Provide warmth and plenty of light – a sunny windowsill or grow lights work well. Remember our springs are late, so don’t jump the gun if there's still snow on the ground!

Transplanting mustard greens outdoors should happen from mid May through late June. This gets them established before the heat of midsummer. Before transplanting, 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 on the weather – late frosts can still happen, so be ready to cover your transplants if needed. The intense sun can also be harsh on young plants, so provide some temporary shade if necessary.

Direct sowing mustard greens is a great option in our Mountain climate, as it avoids transplant shock and lets the plants establish strong roots. Sow seeds directly into the garden from early May through early July. This allows for multiple harvests.

Ensure the soil is well-prepared and has warmed up a bit. Mustard greens germinate best when the soil temperature is around 60-70°F. Sow seeds about ½ inch deep and space them 6-12 inches apart. Thin seedlings as needed once they emerge.

Watering is critical for mustard greens, especially in our dry Mountain climate. Consistent moisture is key to preventing bolting and maintaining good flavor. Aim to keep the soil consistently moist, but not waterlogged.

During the spring, when temperatures are cooler, you might only need to water once or twice a week. As summer heats up and the sun intensifies, increase watering to every other day, or even daily during the hottest stretches. Always check the soil moisture before watering. Stick your finger about 2 inches deep – if it feels dry, it's time to water.

In general, provide about 1 inch of water per week, either through rainfall or irrigation. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases, although our low humidity helps mitigate this. Signs of underwatering include wilting leaves and a bitter taste. Overwatering can lead to yellowing leaves and root rot. A layer of mulch can help retain soil moisture and regulate soil temperature.

You can expect your first harvest of mustard greens from mid June through mid September, about 45 days after planting. The best time to harvest is when the leaves are young and tender. These younger leaves have a milder, more pleasant flavor.

Harvest individual leaves by snipping them off at the base of the plant, leaving the central rosette intact. This encourages continued production throughout the season. As the first frost approaches in early September, harvest any remaining leaves. Larger leaves can be spicier. Remove any flower stalks to prolong the harvest and prevent the leaves from becoming too bitter.

Here are some common problems you might encounter with mustard greens in the Mountain West:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves, especially on young seedlings. You might also see small dark beetles that jump when disturbed.
• What causes it: Small jumping beetles that feed on leaves. They are most damaging to small, young plants.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until plants are larger. Kaolin clay coating can also deter them. Neem oil spray can help control infestations. Healthy 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 may be present, and new growth might be curled or distorted.
• What causes it: Rapidly reproducing sap-sucking insects. Populations can explode in warm weather.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage natural predators like ladybugs and lacewings. Insecticidal soap can be used for heavy infestations. Avoid excess nitrogen fertilizer, which attracts them.

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. You'll notice irregular holes chewed in leaves and dark green droppings. White butterflies might be hovering around your plants.
• What causes it: Larvae of white cabbage butterflies.
• How to fix/prevent it: Bt spray is very effective. Floating row covers can prevent egg laying. You can also handpick caterpillars.

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.
• How to fix/prevent it: Time your plantings for cooler weather. Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep the soil cool. Harvest before bolting progresses too far.

Mountain West Specific Challenges: Our intense sun and moderate-at-altitude heat can stress mustard greens, making them more susceptible to bolting and pest damage. Low humidity can help prevent some fungal diseases, but it also means you need to be vigilant about watering. The dry rainfall also means you'll be relying on irrigation more often than not.

Companion planting can be beneficial for mustard greens. Plant them near onions and garlic, as their strong scents deter pests like aphids and flea beetles. Beets are also good companions, as they don't compete for the same nutrients. Dill attracts beneficial insects that prey on pests. Lettuce provides ground cover and helps retain moisture.

Avoid planting mustard greens near strawberries or tomatoes. Strawberries are susceptible to similar pests and diseases, and tomatoes can stunt the growth of mustard greens. Careful companion planting can help your mustard greens thrive in our unique Mountain West growing conditions.