Jalapeño Peppers in Zone 7A — Mountain West

Jalapeño Peppers are a fantastic addition to any Mountain West garden. Their spicy kick adds zest to our dishes, and they're incredibly versatile for everything from salsas to stuffing. Plus, there’s real satisfaction in harvesting your own peppers, especially when our cool nights even in summer help concentrate their flavor.

Our high altitude and short season present some challenges, but with a little planning, you can absolutely grow a bumper crop of Jalapeños. Our 173-day growing season is enough time to get these peppers from seed to harvest if you start them indoors early.

Starting Jalapeño seeds indoors is the way to go here in the Mountain West, giving them a head start before our late spring arrives. Aim to sow your seeds indoors from early to late March, about 8 weeks before you plan to transplant them outside. You have about a 3-week window.

Use seed trays or small pots filled with a good seed-starting mix. Keep them consistently warm, around 75-80°F, and provide plenty of light – a grow light works wonders. A heat mat can help with germination. I like to bottom-water my seedlings to encourage strong root growth.

Remember, our spring weather can be unpredictable, so don't rush to put them out too early.

Transplant your Jalapeño seedlings outdoors from early May through early June, after the risk of frost has passed. You have a good month to get them in the ground. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week.

Choose a sunny spot with well-draining soil. Space your plants 14-18 inches apart. Be mindful of potential late-season frosts, and have row covers ready to protect your young plants if needed.

Jalapeño Peppers need consistent, moderate watering, but overwatering is a common mistake in our region. Our low humidity means the soil can dry out quickly, but the alkaline soil retains water well.

During the heat of summer (moderate-at-altitude), aim for about 1-2 inches of water per week, depending on rainfall. Use the "finger test" – stick your finger about 2 inches into the soil. If it feels dry, it's time to water. Water deeply at the base of the plant to avoid wetting the foliage, which is especially helpful in our low humidity.

Wilting leaves are a sign of underwatering, while yellowing leaves can indicate overwatering. Mulching around your plants with straw or wood chips helps retain moisture and regulate soil temperature, especially with the intense sun at our altitude.

While not always essential, providing some support for your Jalapeño plants can be beneficial, especially as they become laden with fruit. Their bush habit means they can get top-heavy.

A simple stake works well to keep the plant upright and prevent branches from breaking. Install the stake at planting time to avoid disturbing the roots later. Gently tie the main stem to the stake with soft twine or plant tape, allowing room for growth.

Pruning Jalapeño Peppers isn't strictly necessary, but a little maintenance can improve your harvest.

Pinch off any early flowers that appear to encourage the plant to focus on vegetative growth and develop a stronger root system. If you prefer smooth peppers, remove any fruit that develops corking lines. As the first frost approaches in early October, you can remove any remaining flowers to direct the plant's energy into ripening existing peppers.

You can expect your first Jalapeño harvest from mid-July through early September, about 75 days after transplanting.

Harvest the peppers when they are 3-4 inches long and green, or wait for them to turn red for a sweeter, hotter flavor. Corking lines on the pepper indicate maturity. Use pruning shears or a sharp knife to cut the peppers from the plant, being careful not to damage the branches.

Regular harvesting encourages continued production. As the first frost approaches in early October, harvest all remaining peppers, even the green ones. Green peppers will ripen indoors if stored in a paper bag with an apple or banana.

Here are some common problems you might encounter growing Jalapeño Peppers in the Mountain West:

Blossom Drop

• What it looks like: Flowers fall off without setting fruit. Small fruit yellows and drops. The plant looks healthy but produces no peppers.
• What causes it: Temperature stress is the main culprit. Peppers don't set fruit well when nights stay above 75°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 fertilizer. Try hand-pollination, gently shaking the plant to distribute pollen.

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: These sap-sucking insects reproduce rapidly, especially in warm weather. Ant colonies may farm them for honeydew.
• How to fix/prevent it: A strong spray of water from the hose can knock them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap works well for heavy infestations. Neem oil can also be effective. Avoid excess nitrogen fertilizer, which attracts them.

Pepper Maggots

• What it looks like: Small, white, legless larvae tunneling inside pepper fruits. Damaged or distorted peppers. Premature fruit drop. Small entry holes on the pepper surface.
• What causes it: Adult pepper fruit flies lay eggs on developing peppers. The larvae hatch and burrow into the fruit, feeding on the flesh.
• How to fix/prevent it: Use sticky yellow traps to catch adult flies. Inspect peppers regularly for signs of damage. Remove and destroy infested peppers. Use row covers to prevent flies from laying eggs on the fruit. Insecticides can be used, but be sure to follow label instructions carefully.

Bacterial Leaf Spot

• What it looks like: Small, dark, water-soaked spots on leaves that eventually turn brown or black. Spots may have a yellow halo. Lesions can also appear on stems and fruit.
• What causes it: A bacterial pathogen that thrives in warm, humid conditions. Spread by splashing water, insects, or contaminated tools.
• How to fix/prevent it: Remove and destroy infected leaves. Avoid overhead watering. Improve air circulation by spacing plants properly. Use copper-based fungicides as a preventative measure. Sanitize tools regularly. Choose disease-resistant varieties.

Mountain West Specific Challenges: The intense sun at our high altitude can stress plants, making them more susceptible to problems. Our low humidity helps reduce the risk of fungal diseases, but it also means we need to be vigilant about watering. The alkaline soil can lock out certain nutrients, so amend your soil with compost to improve nutrient availability.

Companion planting can really give your Jalapeños a boost here in the Mountain West.

Tomatoes make great companions because they enjoy similar growing conditions – full sun and well-drained soil. Basil is another excellent choice; it repels pests like aphids and whiteflies and is said to improve the flavor of peppers. Carrots help loosen the soil and attract beneficial insects. Onions also deter pests and can help prevent fungal diseases.

Avoid planting fennel or kohlrabi near your Jalapeños. Fennel inhibits the growth of many plants, and kohlrabi can attract pests that also target peppers.