Planting Guides

When to Plant Peppers in Denver: Complete Guide + Best Varieties for Zone 5a

Denver, Colorado

USDA Zone 5a

Last Frost: May 10

Last updated: November 30, 2025

Learn when to plant peppers in Denver with specific dates for Zone 5a's 148-day growing season and May 9 last frost date.

NNathan Brooks

November 30, 2025

Pepper plants growing in Denver garden with Colorado mountains in background — — Image © PlantReference.org 2026

Quick Answer

Start pepper seeds indoors March 15-22 in Denver for Zone 5a's May 9 last frost. Transplant outdoors May 16-23 when soil temperatures reach 60°F consistently.

TL;DR

Start pepper seeds indoors March 15-22 for Denver's May 9 last frost date. Transplant outdoors May 16-23 when soil warms above 60°F. Choose fast-maturing varieties like Capsicum annuum 'Shishito' and Capsicum annuum 'Sweet Banana' for Zone 5a's 148-day growing season. Use black plastic mulch and protective row covers for best results in Denver's variable spring weather.

Frequently Asked Questions

Can I direct sow pepper seeds in Denver?

Direct sowing pepper seeds in Denver soil is not recommended for Zone 5a. Pepper seeds require consistent soil temperatures above 70°F (21°C) to germinate, which doesn't occur reliably in Denver until mid-June—too late for most varieties to mature before October's first frost. Even with soil amendment and black plastic mulch, spring soil temperatures remain too variable for dependable germination.

Do I need a greenhouse to grow peppers in Denver?

A greenhouse isn't required for most pepper varieties in Denver, but it significantly expands your options and extends the season. Standard varieties like [[Growing Jalapeño Peppers]] and Capsicum annuum 'Sweet Banana' grow successfully outdoors with proper timing and protection.

When should I start hardening off pepper seedlings in Denver?

Begin hardening off pepper seedlings during the first week of May in Denver, timing this process with the approach of the average May 9 last frost date. Denver's dramatic temperature swings make gradual acclimation crucial for transplant success.

What's the latest I can plant peppers in Denver and still get a harvest?

The absolute latest transplant date for peppers in Denver is June 15 for early varieties only. This timing allows approximately 110 days until Denver's October 4 average first frost date, sufficient for Capsicum annuum 'Shishito' (60-70 days) and Capsicum annuum 'Sweet Banana' (65-75 days) to produce harvestable fruit.

How do I protect peppers from Denver's hail storms?

Hail protection is essential for pepper growing in Denver's "Hail Alley" location. Install 1/4-inch (0.6 cm) mesh hail netting over garden beds, supported by PVC hoops or metal framework that keeps netting 12-18 inches (30-45 cm) above plant tops. This permanent protection works throughout the May-August hail season without impeding growth.

Can I grow hot peppers like habaneros successfully in Denver?

Growing Capsicum chinense 'Habanero' peppers in Denver's Zone 5a climate is extremely challenging without season extension. Habaneros require 90-120 days of consistent heat—longer than Denver's 148-day growing season allows when accounting for cool spring and fall periods.

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Tagged with

#denver gardening #zone 5a peppers #colorado vegetables #pepper planting dates #high altitude gardening #denver frost dates #pepper varieties colorado #front range gardening #denver growing season #pepper transplanting

Written By

Nathan Brooks

Nathan is a garden designer in Denver who focuses on water-wise plantings adapted to Colorado's Front Range climate. He grew up in Nebraska, studied environmental science in college, and fell into garden design after spending summers working at a native plant nursery in Fort Collins. Denver's climate is genuinely challenging—low humidity, intense UV, alkaline clay soil, and wild temperature swings that can go from 70°F to snow in 24 hours. Nathan designs gardens that handle all of that without supplemental irrigation once established. He writes about xeric gardening, native plant selection for the Front Range, and the practical realities of high-altitude growing.