Sweet Peppers in Zone 6B — Mountain West

Sweet peppers are a fantastic addition to any Mountain West garden. Their sweet, crisp flavor shines in everything from summer salads to grilled skewers, and the satisfaction of harvesting colorful peppers you grew yourself is hard to beat. Plus, cool nights even in summer intensify their sweetness.

High altitude gardening has its challenges: intense sun, alkaline soil, and our short season. But with a little planning and attention to timing, you can absolutely enjoy a bountiful sweet pepper harvest. Our 163-day growing season is plenty if you start indoors and choose the right varieties.

Starting your sweet pepper seeds indoors is essential in our climate to get a head start on the short growing season. Begin in early to late March, about 8 weeks before you plan to transplant them outside. This gives them plenty of time to mature before our first frost arrives in early October.

Use seed trays or small pots filled with a good-quality seed-starting mix. Keep the soil consistently moist but not soggy, and consider bottom watering to avoid damping off. Place the trays in a warm location (around 75-80°F) and provide plenty of light, either from a sunny window or a grow light. Remember, our spring weather can be unpredictable, so indoor starts are key!

Transplant your sweet pepper seedlings outdoors from early May through early June, once the danger of 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 of our region.

Choose a sunny spot in your garden with well-drained soil and space the plants 18-24 inches apart. Be mindful of potential late-season frosts and have row covers ready to protect your young plants if needed. Our spring weather can be a bit wild!

Consistent watering is vital for sweet peppers in our dry Mountain West climate. The key is to provide enough water to keep the soil consistently moist, but not waterlogged. Aim for about 1-2 inches of water per week, depending on rainfall.

Use the "finger test" to check the soil moisture: stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Water deeply at the base of the plant to encourage strong root growth and reduce the risk of foliar diseases in our low-humidity environment. Avoid overhead watering, which can lead to fungal issues.

Signs of underwatering include wilting leaves and stunted growth. Overwatering, on the other hand, can cause yellowing leaves and root rot. Mulching around your pepper plants with straw or wood chips helps retain moisture and regulate soil temperature, which is especially helpful with our temperature swings.

While not always necessary, providing support for your sweet pepper plants can be beneficial, especially as they become laden with fruit. Bush-type peppers can get quite heavy, and staking prevents branches from breaking.

Tomato cages or individual stakes work well for supporting sweet peppers. Install the supports at planting time to avoid disturbing the roots later. As the plants grow, gently tie the stems to the supports using soft twine or plant ties.

Pinching off the first few flowers that appear on your sweet pepper plants is a common practice that encourages stronger growth and higher overall yields. It might seem counterintuitive, but removing these early flowers directs the plant's energy into developing a strong root system and leafy growth.

Simply pinch off the flowers as soon as they appear. As the season progresses, remove any yellowing or damaged leaves to improve air circulation. Towards the end of the season, as our first frost approaches in early October, consider removing any new flowers that won't have time to develop into mature peppers. This will help the plant focus its energy on ripening the existing fruit.

You can expect your first sweet pepper harvest from mid July through late August, about 65 days after transplanting. Look for peppers that have reached their full size and color for the variety you're growing. Sweet peppers get sweeter the longer they ripen on the plant, so don't be afraid to let them stay on the vine until they're fully colored.

To harvest, use sharp scissors or pruning shears to cut the pepper from the plant, leaving a short stem attached. Regular harvesting encourages the plant to continue producing more peppers. As the first frost approaches in early October, harvest any remaining peppers, even if they're still green. These can be ripened indoors by placing them in a paper bag with an apple or banana.

Even with the best care, sweet pepper plants can sometimes encounter problems. Here are a few common issues we see in the Mountain West:

• Blossom Drop
• What it looks like: Flowers fall off without setting fruit. Small fruit yellows and drops. Plant looks healthy but produces no fruit.
• What causes it: Temperature stress. Peppers don't set fruit well when nights stay above 75°F or days exceed 95°F. Low humidity, excess nitrogen, or poor pollination can also contribute.
• How to fix/prevent it: Be patient — fruit set resumes when temperatures moderate. Provide afternoon shade during extreme heat. Keep plants well-watered. Avoid excess nitrogen. Try hand-pollination.
• 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: Rapid-reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may farm them for honeydew.
• How to fix/prevent it: Strong water spray knocks them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer (it attracts them).
• Sunscald
• What it looks like: White, papery patches on fruit exposed to direct sun. Affected areas may blister and become susceptible to rot.
• What causes it: Intense, direct sunlight on fruit — usually after leaves are removed or lost to disease, suddenly exposing previously shaded fruit. High altitude sun makes this more likely.
• How to fix/prevent it: Don't over-prune foliage. Use shade cloth in extreme heat. Maintain healthy foliage to shade fruit naturally. If fruit is already exposed, drape a small piece of row cover over it.
• Blossom End Rot
• What it looks like: Sunken, dark brown or black leathery patch on the bottom (blossom end) of fruit. Often affects first fruits of the season.
• What causes it: Calcium deficiency caused by inconsistent watering. Not a disease — it's a nutrient uptake problem triggered by drought/flood cycles.
• How to fix/prevent it: Water consistently (the single most effective fix). Mulch heavily to maintain even soil moisture. Don't over-fertilize with nitrogen. Calcium sprays help marginally. Remove affected fruit.

Mountain West Specific Challenges: Our moderate-at-altitude summer heat, combined with low humidity and dry rainfall, can create challenges for sweet pepper plants. Consistent watering is key to preventing blossom end rot and blossom drop. The intense UV at high altitude can also lead to sunscald, so be sure to provide adequate shade during the hottest part of the day.

Companion planting can be a great way to improve the health and productivity of your sweet pepper plants. Tomatoes make excellent companions, as they share similar growing requirements and can provide shade for each other during the hottest part of the day. Basil is another great choice, as it repels aphids and other pests.

Carrots and onions can also be beneficial companions, as they help to deter soil-borne pests. Spinach can be planted between pepper plants to provide ground cover and help retain moisture. Avoid planting fennel, kohlrabi, or brassicas (like cabbage and broccoli) near your sweet peppers, as they can inhibit growth or attract pests.