When To Plant Peppers In Colorado

If you’re planning your Colorado vegetable garden, knowing exactly when to plant peppers is the key to a big harvest. Getting the timing right makes all the difference in our unique climate, where a late frost can set you back and a short growing season demands efficiency.

Peppers are warm-season lovers that need a long, sunny period to produce well. Planting them too early in cold soil will stunt them, while planting to late means your fruits might not mature before the first fall frost. This guide will walk you through the optimal schedule and techniques for success.

This is the core question for every Colorado gardener. The simple answer is: you transplant pepper seedlings outdoors after the last spring frost date has safely passed and soil temperatures have warmed. Rushing this date is the most common mistake.

For most of Colorado’s Front Range and urban areas, the average last frost falls between May 5th and May 15th. In mountain towns and higher elevations, it can be as late as early or even mid-June. Always check your local frost dates, as microclimates vary widely.

Understanding Your Colorado Growing Zone

Colorado spans USDA Hardiness Zones 3 through 7. This huge range affects your planting calendar directly.

Zones 5-7 (Front Range, Grand Junction, Pueblo): Target transplanting around mid-May. You can often start seeds indoors in early to mid-March.
Zones 3-4 (High Mountain Valleys, San Luis Valley): Wait until early to mid-June. Start seeds indoors in early April to have robust plants ready.

Your local county extension office is a fantastic resource for hyper-local advice.

The Critical Role of Soil Temperature

Air temperature is only half the story. Pepper roots hate cold soil. Use a soil thermometer to check at a 2-inch depth.

Ideal Minimum: 60°F (70°F is even better for rapid growth).
Danger Zone: Planting in soil below 55°F can shock plants, causing them to sit dormant or become susceptible to disease.

If your soil is still cool past your frost date, be patient. Warm it faster by using black plastic mulch for a week or two before planting.

Starting Peppers From Seed Indoors

Because of our short season, starting peppers from seed indoors is almost essential for good harvests. They need a long head start.

Timing: Sow seeds 8-10 weeks before your planned outdoor transplant date. For a mid-May planting, start seeds in early March.
Method: Plant seeds ¼ inch deep in a seed-starting mix. Use a heat mat to maintain soil temperature around 80°F for best germination, which can be slow (up to 2-3 weeks).
Growing On: Provide strong light (a south window is rarely enough; use grow lights). Keep seedlings consistently moist but not soggy.

The Hardening Off Process

Never move tender seedlings directly from indoors to the garden. They need a gradual transition called hardening off.

About 7-10 days before transplanting, begin placing seedlings outdoors in a shaded, sheltered spot for just 1-2 hours.
Gradually increase their time outside and their exposure to direct sun over the week.
By the end, they should be able to handle full sun and gentle breeze all day and stay out overnight if temps are safe.

This step toughens their stems and reduces transplant shock, which is crucial for Colorado’s intense sun.

Choosing the Right Pepper Varieties for Colorado

Selecting varieties with shorter “days to maturity” (DTM) increases your success rate. Look for DTM under 75 days for higher elevations, and up to 85 days for warmer zones.

Quick Producers (Great for everywhere): ‘Ace’ Bell (50 DTM), ‘Early Jalapeño’ (60 DTM), ‘Hungarian Wax’ (65 DTM).
Good for Warmer Areas (Zones 5-7): ‘Carmen’ Italian Sweet (70 DTM), ‘Poblano’ (70 DTM), ‘Sugar Rush Peach’ (80 DTM).
For a Challenge (Need season extenders): Large bell peppers (80+ DTM) or super-hot varieties like ‘Ghost Pepper’ (100+ DTM).

Step-by-Step Outdoor Planting Guide

Site Selection: Choose the sunniest spot in your garden—at least 8 hours of direct sun. Ensure good drainage.
Soil Prep: Amend Colorado’s often clay-heavy soil with 3-4 inches of compost. Peppers prefer a slightly acidic to neutral pH (6.0-7.0).
Planting: Transplant on a cloudy afternoon or evening. Dig a hole slightly deeper than the root ball. Space plants 18-24 inches apart in rows 24-36 inches apart.
Deep Planting (Optional): Unlike tomatoes, peppers shouldn’t be buried deeply along the stem. Plant them at the same depth they were in their pot.
Water & Mulch: Water deeply immediately after planting. Apply 2-3 inches of organic mulch (straw, wood chips) to retain moisture and regulate soil temp.

Protecting Your Peppers from Colorado Weather

Our weather is unpredictable. Have protection methods ready.

Frost Protection: Keep row covers, cloches, or old bedsheets handy for unexpected late or early frosts. Even a plastic gallon jug with the bottom cut out can work.
Wind: Use a windbreak or plant near a fence if your area is windy. Staking plants early also provides support.
Intense Sun: If a newly planted seedling shows signs of scorching, provide temporary shade for a few days with a shade cloth or even a lattice propped over it.

Season Extension Techniques

To get more from your peppers, start early and end late.

Walls of Water: These plastic teepees surround plants, creating a mini-greenhouse that can let you plant 2-3 weeks earlier.
Cold Frames & Hoop Houses: Ideal for both early spring planting and protecting plants into the first fall frosts, often extending harvest by a month or more.
Container Growing: Growing peppers in pots allows you to move them to sheltered areas (like a garage) during early or late cold snaps.

Common Colorado Pepper Growing Problems

Stay vigilant for these issues:

Blossom End Rot: Dark, sunken spots on fruit bottoms. Caused by inconsistent watering and calcium uptake. Keep soil evenly moist and ensure proper pH.
Sunscald: Pale, leathery patches on fruits exposed to direct, intense sun. Provide light shade during peak summer heat or ensure good leaf coverage.
Poor Fruit Set: If flowers bloom but no fruit forms, it’s often due to nighttime temperatures below 60°F or above 90°F. Be patient for weather to improve.
Pests: Aphids and flea beetles are common. Spray aphids with a strong stream of water; use floating row covers for beetles early in the season.

FAQ: Planting Peppers in Colorado

What is the absolute last date to plant peppers in Colorado?

For most areas, aim to have transplants in the ground by mid-June at the absolute latest. This gives them enough time to establish and produce before fall frost. Starting from seed outdoors directly is not recommended except in our very warmest, longest-season valleys.

Can I plant peppers in July in Colorado?

Planting peppers in July from a transplant is generally to late for them to reach full production before frost, unless you are using strong season extension methods. You might get a few fruits, but it’s not optimal.

How do I get my peppers to turn color?

Peppers start green and mature to their final color (red, yellow, orange, etc.). This process requires time and warmth. If your peppers are staying green as frost approaches, you can harvest them and they will often continue to ripen indoors on a sunny windowsill.

Should I use fertilizer for peppers in Colorado soil?

Yes, but go easy. To much nitrogen promotes leafy growth at the expense of fruit. At planting, use a balanced fertilizer or one higher in phosphorus. Once flowers appear, a fertilizer lower in nitrogen and higher in potassium can help fruit development.

By following this Colorado-specific schedule—waiting for warm soil, starting seeds indoors, choosing smart varieties, and being ready to protect your plants—you’ll give your peppers the best possible start. With careful attention, you can enjoy a productive pepper harvest from midsummer right up until the first snow flies.