Snap Peas in Zone 5A — Mountain West

Snap peas are a fantastic addition to any Mountain West garden. Their crisp, sweet pods are delicious raw, stir-fried, or added to salads. Plus, the satisfaction of harvesting fresh, homegrown snap peas in our short growing season is hard to beat, and our cool nights even in summer enhance their sweetness.

While high altitude gardening presents challenges like intense sun and a short season, snap peas are surprisingly well-suited. With a 138-day growing season, you can easily fit in a spring and fall crop. Careful timing and variety selection will help you overcome our climate's unique hurdles.

Transplanting snap peas outdoors is an option, though direct sowing is often preferred. If you start seeds indoors, transplant seedlings outdoors from mid April through early May, after hardening them off. Hardening off involves gradually exposing your seedlings to outdoor conditions for about a week.

When transplanting, space plants 3-4 inches apart. Keep an eye on the weather forecast. Late frosts can still occur, so be prepared to cover your young plants if temperatures dip. The intense sun can also stress young transplants, so consider providing temporary shade cloth protection if needed.

Direct sowing is the recommended method for snap peas in our region. You can sow seeds directly into the garden from late March through mid July. Snap peas are quite hardy and can handle some cool soil temperatures, just like garden peas.

Prepare your soil by loosening it and adding compost. Ensure the soil temperature is at least 40°F. Sow seeds 1-2 inches deep and 3-4 inches apart. Keep the soil consistently moist until germination, which usually takes about a week. Succession planting every few weeks will provide a continuous harvest.

Snap peas need consistent moisture to produce plump, sweet pods, but they don't like soggy soil. In our dry Mountain West climate, this requires a bit of attention. Aim for about 1 inch of water per week, especially during pod development.

The best way to gauge watering needs is the "finger test." Stick your finger into the soil about 2 inches deep. If it feels dry, it's time to water. Water at the base of the plants to avoid wetting the foliage, which can encourage powdery mildew in our moderate-at-altitude summer heat and low humidity.

In spring, with cooler temperatures, you might only need to water once a week. As the summer heat intensifies, increase watering to two or three times a week. Signs of underwatering include wilting leaves and shriveled pods. Overwatering can lead to yellowing leaves and root rot. A layer of mulch around your plants will help retain moisture and keep the soil cool, a boon in our intense sunlight.

Snap peas are vining plants and need support to climb. A trellis, chicken wire, or even pea brush works well. Aim for a support that's 4-6 feet tall, as some varieties can get quite large.

Install the support at planting time to avoid disturbing the roots later. As the plants grow, gently train them to climb the support. They'll naturally start grabbing on with their tendrils, but you may need to guide them initially.

You can expect your first snap pea harvest from late May through early October, depending on when you planted. Snap peas are ready to harvest when the pods are plump, crisp, and the peas inside are fully developed. The pods should be bright green and snap easily when bent.

Harvest by gently snapping the pods off the vine, being careful not to damage the plant. Regular harvesting encourages continued production. Check your plants every few days, as snap peas can mature quickly. As the first frost approaches in late September, harvest any remaining pods, even if they're not quite fully ripe. They can still be used in stir-fries or soups.

Here are some common problems you might encounter with snap peas in the Mountain West:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes pods. Leaves curl, yellow, and die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it.
• How to fix/prevent it: Improve air circulation through spacing and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays help. Milk spray (1 part milk to 9 parts water) is surprisingly effective. Plant resistant varieties.

Pea Aphids

• What it looks like: Small, soft-bodied insects clustered on stems, leaves, and pods. Leaves may be curled, distorted, or yellowed. Sticky honeydew (aphid excrement) may be present.
• What causes it: Aphids are attracted to stressed plants and can multiply rapidly in favorable conditions. Our high altitude and intense UV can stress plants.
• How to fix/prevent it: Blast aphids off plants with a strong stream of water. Introduce beneficial insects like ladybugs and lacewings. Insecticidal soap or neem oil can also be used.

Root Rot

• What it looks like: Yellowing leaves, stunted growth, wilting, and mushy, brown roots.
• What causes it: Overwatering and poorly drained soil create conditions favorable for soilborne fungi that attack roots. Heavy clay soils common in the Mountain West can exacerbate this.
• How to fix/prevent it: Improve soil drainage by adding compost and other organic matter. Avoid overwatering. Ensure good air circulation around plants.

Fusarium Wilt

• What it looks like: Wilting on one side of the plant first, then spreading. Yellow leaves starting on one side. Brown streaks in stem when cut open.
• What causes it: Soil-borne fungus (Fusarium oxysporum). Persists in soil for years. Enters through roots. Warm soil temperatures favor it.
• How to fix/prevent it: No cure once infected — remove and destroy the plant. Plant resistant varieties (look for 'F' on seed labels). Rotate crops on a 4-year cycle. Solarize soil in hot zones. Raise soil pH above 6.5.

Mountain West Specific Challenges: Our moderate-at-altitude summer heat, low humidity, and dry rainfall can create conditions that stress snap peas. Intense sunlight can also scorch leaves if plants aren't adequately watered. Be sure to monitor your plants closely and adjust your watering schedule as needed.

Companion planting can help your snap peas thrive. Carrots and radishes are good companions because they loosen the soil, making it easier for snap peas to establish roots. Cucumbers and corn provide natural trellises for snap peas to climb. Lettuce benefits from the shade provided by snap peas, which helps prevent bolting in our intense sun.

Avoid planting snap peas near onions or garlic. These alliums can inhibit the growth of snap peas. Keep your snap peas happy by choosing the right neighbors in your Mountain West garden.