Bell Peppers in Zone 5A — Mountain West

Bell peppers are a rewarding addition to any high altitude garden. Their sweet, crisp flavor shines in salads and cooked dishes, and the vibrant colors brighten any plate. Growing your own bell peppers, especially in our short season, is deeply satisfying.

Our Mountain West climate presents challenges like intense sun, alkaline soil, and cool nights, but with careful timing and a few tricks, you can harvest a beautiful crop of bell peppers. Our 138-day growing season means starting indoors is essential, but it's absolutely doable.

Starting bell pepper seeds indoors is key to getting a head start in our short growing season. Aim to sow your seeds from late March through mid April, about eight weeks before you plan to transplant them outside. This gives them ample time to develop before our last frost.

Use seed trays or small pots filled with a good quality seed-starting mix. Peppers need warmth to germinate, so a heat mat underneath the trays can really help. Provide plenty of light, either with a grow light or a very sunny south-facing window. Don’t forget to water from the bottom by setting the tray in a shallow container of water until the soil surface is moist.

Remember, spring here in the mountains is known for cool nights and unexpected temperature swings, so keep your seedlings protected indoors until the weather truly settles.

Transplant your bell pepper seedlings outdoors from late May through late June, once the danger of frost has passed. Before planting, 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 temperatures.

Space your pepper plants 18-24 inches apart in a sunny spot with well-draining soil. Our alkaline soil can be amended with compost to improve drainage and nutrient availability. Keep an eye on the forecast; late spring hail is always a concern.

Consistent watering is crucial for bell pepper production, especially in our dry Mountain West climate. Aim for moderate watering, keeping the soil consistently moist but not waterlogged. Bell peppers are not drought tolerant, and inconsistent moisture can lead to blossom end rot and thin-walled fruit.

During the hottest part of the summer (moderate-at-altitude, around 85°F), you'll likely need to water deeply two to three times per week, providing about 1-2 inches of water each time. Use the finger test: stick your finger about two inches into the soil. If it feels dry, it's time to water. Given our low humidity, watering at the base of the plant is preferable to overhead watering, which can encourage fungal diseases in more humid climates.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can cause yellowing leaves and root rot. A layer of mulch around your plants will help retain moisture and regulate soil temperature, which is especially helpful given our intense sun and cool nights.

Bell pepper plants can benefit from support, especially as they become loaded with fruit. The weight of the peppers can cause branches to break or the entire plant to topple over, particularly after a summer storm.

A simple stake or tomato cage works well. Install the support at planting time to avoid disturbing the roots later. As the plant grows, gently tie the stems to the stake with soft twine, providing support without constricting the plant. This is especially important for larger bell pepper varieties.

Pruning bell peppers can encourage better fruit production and airflow. Pinch off any early flowers that appear before the plant is well-established; this directs the plant's energy towards vegetative growth, resulting in a stronger plant and more peppers later in the season.

Remove any fruit that touches the ground to prevent rot. Throughout the season, prune out any interior branches that are crowded or crossing, which improves airflow and reduces the risk of disease. As the first frost approaches in late September, you can remove any new flowers that are unlikely to mature before the cold weather arrives.

You can expect your first bell pepper harvest from early August through mid September, about 70 days after transplanting. Bell peppers are ready to harvest when they are full size and firm. They can be harvested green at their immature stage, but the flavor is sweetest when they are fully colored red, yellow, or orange.

To harvest, use sharp pruners or scissors to cut the pepper from the plant, leaving a short stem attached. Regular harvesting encourages continued production, so pick peppers as they ripen. As the first frost approaches in late September, harvest any remaining peppers, even if they are still green.

Green peppers will ripen indoors if stored in a paper bag with an apple or banana. The ethylene gas emitted by these fruits helps to speed up the ripening process.

Bell peppers can encounter a few common problems in our Mountain West gardens:

Blossom End Rot

• What it looks like: Sunken, dark brown or black leathery patch on the bottom of the fruit.
• What causes it: Calcium deficiency caused by inconsistent watering. Our dry climate and alkaline soil exacerbate this issue.
• How to fix/prevent it: Water consistently, especially during dry spells. Mulch heavily to maintain even soil moisture. Avoid over-fertilizing with nitrogen. Remove affected fruit.

Blossom Drop

• What it looks like: Flowers fall off without setting fruit. Small fruit yellows and drops.
• What causes it: Temperature stress, especially cool nights. Our high altitude can lead to significant temperature fluctuations.
• 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.

Aphids

• What it looks like: Clusters of tiny soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue.
• What causes it: Rapid-reproducing sap-sucking insects. Populations explode in warm weather.
• How to fix/prevent it: Strong water spray knocks them off. Encourage ladybugs and lacewings. Insecticidal soap or neem oil for heavy infestations.

Sunscald

• What it looks like: White, papery patches on fruit exposed to direct sun.
• What causes it: Intense, direct sunlight on fruit, common in our high altitude.
• How to fix/prevent it: Don't over-prune foliage. Use shade cloth in extreme heat. Maintain healthy foliage to shade fruit naturally.

Mountain West Specific Challenges: Our moderate-at-altitude heat, combined with low humidity and infrequent rainfall, means consistent watering and protection from intense UV are vital for successful bell pepper growing. Monitor your plants closely and adjust your care as needed.

Companion planting can benefit bell peppers in our Mountain West gardens. Tomatoes make good companions because they share similar growing requirements and can provide some shade during our hot afternoons. Basil is also a great choice, as it repels pests like aphids and whiteflies.

Carrots and onions are beneficial because they attract beneficial insects and deter pests. Spinach can be planted as a ground cover to help retain moisture and suppress weeds. Avoid planting bell peppers near fennel, which inhibits their growth. Also, kohlrabi and other brassicas like cabbage and broccoli should be avoided as they can compete for nutrients and attract similar pests.