Sweet Peppers in Zone 5B — Mountain West

Sweet peppers are a rewarding crop for the Mountain West gardener. Their sweet, crisp flavor shines in summer salads, grilled dishes, and vibrant salsas. Plus, there's nothing quite like the satisfaction of biting into a sun-ripened pepper you grew yourself, especially when our cool nights here seem to concentrate the sweetness.

Our high altitude, intense sun, and short growing season definitely present challenges for warm-season crops like peppers. But with careful timing and a few tricks, you can absolutely enjoy a bountiful harvest within our 149-day growing season.

Starting your sweet pepper seeds indoors is essential for high altitude gardening. This gives them a head start before the risk of frost is completely gone in mid-May through mid-June. You'll want to sow your seeds indoors mid-March through early April, about eight weeks before you plan to transplant them outside.

Use seed trays or small pots filled with a good seed-starting mix. Keep them consistently warm (around 75-80°F) using a heat mat, and provide plenty of light with grow lights. Bottom watering is a great way to keep the soil consistently moist without risking damping off. Remember, spring here can be unpredictable, so be patient and don't rush the process.

Transplanting your sweet pepper seedlings outdoors mid-May through mid-June is a critical step. Before transplanting, be sure to 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 nights.

Plant your seedlings 18-24 inches apart in a sunny spot with well-drained soil. Even in late spring, keep an eye on the weather forecast for any late frosts. A frost blanket can be a lifesaver if temperatures dip unexpectedly.

Consistent watering is key to growing sweet, thick-walled peppers in our dry Mountain climate. While we don't have the humidity issues of other regions, we also don't get much rain, so you'll need to be diligent. Aim for consistent moisture, but avoid soggy soil.

During the hottest part of the summer, you'll likely need to water your pepper plants deeply a couple of times a week. Use the "finger test" – if the soil feels dry about two inches down, it's time to water. Give them about 1-2 inches of water each time. Water at the base of the plant to avoid wetting the foliage, which can lead to fungal problems.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can cause yellowing leaves and root rot. A layer of mulch, like straw or wood chips, can help retain moisture and regulate soil temperature.

While not always necessary, providing support for your sweet pepper plants can be beneficial, especially as they become laden with fruit. Some varieties tend to get quite bushy. Choose determinate varieties for better support, and consider that fruit load is a factor.

Staking is a simple and effective method. Insert a sturdy stake near each plant at planting time and gently tie the main stem to the stake as it grows. Cages also work well, providing all-around support.

Pruning sweet peppers is fairly minimal, but a little attention can boost your harvest. Pinching off the first few flowers that appear on the plant encourages it to focus its energy on vegetative growth, resulting in a stronger plant and higher overall yields later in the season.

Throughout the season, you can remove any yellowing or damaged leaves. As the first frost approaches in early October, you can remove any small, immature peppers to encourage the plant to focus on ripening the larger ones before the cold hits.

You can expect your first sweet pepper harvest late July through early September, about 65 days after transplanting. The best indicator of ripeness is the full size and color typical for the variety you're growing. Remember, sweet peppers get sweeter the longer they ripen on the plant.

Harvest peppers by using pruning shears or a sharp knife to cut the stem just above the fruit. Be careful not to damage the plant. Regular harvesting encourages continued production. As the first frost approaches, harvest all remaining peppers, even the green ones.

Green peppers can ripen indoors if kept in a warm, sunny location.

Here are some common problems you might encounter growing sweet peppers in the Mountain West:

Blossom Drop

• What it looks like: Flowers fall off without setting fruit, or small fruit yellows and drops.
• What causes it: Temperature stress is a big culprit here. Nights that stay too warm or days with intense sun can prevent fruit set. Low humidity and poor pollination can also contribute.
• How to fix/prevent it: Be patient – fruit set usually resumes when temperatures moderate. Provide afternoon shade during the hottest part of the day. Keep plants well-watered, especially during dry spells. You can also try hand-pollinating the flowers.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. You might also see sticky honeydew or curled leaves.
• What causes it: These sap-sucking insects thrive in warm weather.
• How to fix/prevent it: A strong blast of water from the hose can knock them off. Encourage natural predators like ladybugs. Insecticidal soap or neem oil can be used for heavy infestations. Avoid over-fertilizing with nitrogen.

Sunscald

• What it looks like: White, papery patches on the fruit, usually on the side facing the sun.
• What causes it: Intense, direct sunlight, especially after leaves have been removed or damaged. Our high altitude and intense UV make this a real risk.
• How to fix/prevent it: Avoid over-pruning. If fruit is exposed, drape a small piece of row cover or shade cloth over it.

Blossom End Rot

• What it looks like: A sunken, dark brown or black leathery patch on the bottom of the fruit.
• What causes it: Calcium deficiency due to inconsistent watering. This is common in our dry climate where we often experience cycles of drought and flood.
• How to fix/prevent it: Water consistently! Mulch heavily to maintain even soil moisture. Remove affected fruit.

Mountain West Specific Challenges: The combination of intense sun, low humidity, and dry conditions in the Mountain West can make it challenging to provide the consistent moisture that sweet peppers need. Be vigilant about watering, especially during hot, dry spells, and consider using shade cloth during periods of extreme heat to prevent sunscald and blossom drop.

Companion planting can be a great way to improve the health and productivity of your sweet peppers.

Good companions:

• Tomatoes: They share similar needs (sun, water, nutrients) and can offer mutual support.
• Basil: It repels pests like aphids and whiteflies.
• Carrots: They improve soil drainage and aeration.
• Onions: They deter pests.
• Spinach: Acts as a ground cover, suppressing weeds and retaining moisture.

Bad companions:

• Fennel: It inhibits the growth of many plants.
• Kohlrabi and Brassicas (cabbage, broccoli, cauliflower): They compete for nutrients and attract pests.