Mustard Greens in Zone 3B — Mountain West

Mustard greens are a fantastic, fast-growing crop perfectly suited for our short Mountain West season. Their peppery bite adds zing to salads and stir-fries, and they're surprisingly cold-hardy, tolerating our cool nights even in summer. Plus, the satisfaction of harvesting fresh greens you grew yourself, despite our challenging climate, is hard to beat.

Our high altitude, intense sun, and alkaline soil can make gardening tricky. But with careful timing and a few tricks, you can enjoy a bountiful harvest of mustard greens well within our 108-day growing season. The key is understanding how to work *with* our Mountain climate.

Starting mustard greens indoors is an option, but not always necessary given their fast growth. If you're eager for an extra-early start, aim to sow seeds indoors from mid-April through early May, about three weeks before you intend to transplant. This gives them a head start before our late spring arrives.

Use seed trays or small pots with a good seed-starting mix. Keep them consistently moist by bottom watering to avoid disturbing the tiny seeds. Provide warmth and plenty of light—a sunny windowsill or grow lights work well. Remember, our spring can be slow to arrive, so indoor starts help bridge that gap.

Transplanting mustard greens outdoors can happen from mid-May through late June, once the risk of hard frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense sun and cooler temperatures.

Space plants 6-12 inches apart in rows. Be mindful of potential late frosts that can still occur in May and early June, even though it's rare. If a frost is forecast, cover your transplants with a blanket or cloche for protection.

Direct sowing is a great way to grow mustard greens, especially since they germinate quickly. Sow seeds from late April through mid-July for a continuous harvest. Soil temperatures should be at least 45°F for optimal germination.

Prepare your soil by loosening it and adding compost to improve drainage and fertility. Sow seeds about ½ inch deep and 6-12 inches apart, or sow them closer together and thin later. Direct sowing avoids transplant shock, which can be a benefit in our challenging climate.

Consistent moisture is key to happy mustard greens in our dry Mountain West climate. While they aren't drought-tolerant, overwatering can be just as detrimental. Finding the right balance is crucial.

During the peak of summer, especially when temperatures reach around 85°F, you'll likely need to water deeply about twice a week. Use the "finger test" – if the top two inches of soil feel dry, it's time to water. Aim to provide about one 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 (though our low humidity helps). Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. Mulching around your plants with straw or wood chips helps retain moisture and regulate soil temperature, which is especially helpful given our intense sun.

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, usually around 4-6 inches long. These younger leaves have a milder, more delicate flavor.

Harvest by snipping off the outer leaves with scissors or a knife, leaving the inner leaves to continue growing. This allows for continuous harvesting throughout the season. As the weather cools down in late summer, mustard greens tend to become even sweeter and more flavorful.

As the first frost approaches in early September, harvest any remaining leaves to prevent them from being damaged. You can also cover 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 Mountain West:

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, and they thrive in our dry conditions.
• How to fix/prevent it: Row covers are your best bet for protecting seedlings. You can also delay planting until plants are larger and more resilient. Consider using kaolin clay or neem oil.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. You might also notice sticky honeydew residue and curled or distorted new growth.
• What causes it: Aphids are sap-sucking insects that can multiply rapidly, especially during warm spells.
• How to fix/prevent it: Knock them off with a strong spray of water. Encourage natural predators like ladybugs. Insecticidal soap or neem oil can help with heavy infestations.

Cabbage Worms

• What it looks like: Smooth green caterpillars munching on leaves, leaving irregular holes. You might see dark green droppings and white butterflies fluttering around.
• What causes it: These are the larvae of cabbage butterflies.
• How to fix/prevent it: Bt spray is very effective. Use floating row covers to prevent butterflies from laying eggs. Handpick caterpillars whenever you see them.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk, and the leaves become tough and bitter.
• What causes it: This happens when temperatures rise, signaling the plant to reproduce. Our intense sun can exacerbate this.
• How to fix/prevent it: Time your plantings for cooler periods in spring or fall. Choose bolt-resistant varieties. Provide shade during hot spells, and mulch to keep the soil cool.

Mountain West Specific Challenges: Our moderate-at-altitude heat, low humidity, and dry rainfall can create a stressful environment for mustard greens. The intense sun can lead to bolting, and the dry air can attract pests like flea beetles. Consistent watering and careful monitoring are key to success.

Companion planting can greatly benefit your mustard greens in our Mountain gardens.

Good companions:

• Onion and garlic: These alliums deter pests like aphids and cabbage worms with their strong scent.
• Beets: Beets help loosen the soil, improving drainage, which is beneficial in our sometimes-compacted alkaline soils.
• Dill: Dill attracts beneficial insects like ladybugs and lacewings, which prey on aphids and other pests.
• Lettuce: Growing lettuce alongside mustard greens can provide shade and help keep the soil cool, reducing the risk of bolting.

Bad companions:

• Strawberries: Strawberries and mustard greens compete for nutrients in the soil.
• Tomatoes: Tomatoes can attract pests that also affect mustard greens, such as aphids and whiteflies.