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.

DDr. Sarah Green

November 30, 2025

Pepper plants growing in Denver garden with Colorado mountains in background — — Image © PlantReference.org 2025

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.

Product Recommendations

XLUX Soil Moisture Meter T10 Bonsai Moisture Gauge

https://www.amazon.com/XLUX-T10-Moisture-Sensor-Garden/dp/B014MJ8J2U

This accurate 3-in-1 meter measures soil moisture, pH, and light levels without requiring batteries or calibration. The 7-inch probe reaches pepper root zones effectively, crucial for managing irrigation in Denver's clay soils and arid climate. Features easy-to-read analog display and durable construction for outdoor use. Perfect for preventing both overwatering in clay soil and underwatering during Colorado's hot, dry summers. Helps optimize soil conditions for pepper growth while conserving water in Denver's drought-conscious environment.

Price: $9.99 → $11.99

Johnny's Selected Seeds Certified Organic Pepper Seeds

https://www.johnnyseeds.com/vegetables/peppers/

Professional-grade pepper seeds selected for cold climate performance and disease resistance. Offers proven varieties like 'Shishito' and 'Carmen' that excel in Zone 5a conditions. Seeds undergo rigorous testing for germination rates and genetic purity, ensuring reliable performance in Denver's challenging growing environment. Detailed growing instructions included with variety-specific advice for northern climates. Certified organic options available for sustainable growing practices. Excellent germination rates reduce replanting needs in Denver's short season.

Price: $2.95 → $4.95

Agfabric Plant Cover Freeze Protection 0.55oz Floating Row Cover

https://www.amazon.com/Agfabric-Plant-Cover-Protection-Floating/dp/B01LWRXQ4W

Professional-grade spunbond fabric provides 4-6°F frost protection while allowing air, water, and sunlight penetration. Essential for protecting pepper transplants during Denver's volatile May weather patterns. UV-resistant material withstands Colorado's intense high-altitude sun without degrading. Lightweight 0.55oz weight won't crush tender plants while providing wind protection crucial in Denver's Front Range location. Reusable for multiple seasons with proper storage. Available in various sizes to cover individual plants or entire beds during late spring freeze events.

Price: $14.99 → $24.99

FoxFarm Ocean Forest Potting Soil Mix Indoor Outdoor Plants

https://www.amazon.com/FoxFarm-Ocean-Forest-Potting-Cubic/dp/B000BYCJI2

Premium potting mix combining aged forest products, sphagnum peat moss, and marine-based nutrients ideal for container pepper growing in Denver. pH-balanced between 6.3-6.8, perfect for pepper cultivation without soil amendment needs. Excellent drainage prevents root rot in clay pot conditions while retaining adequate moisture during Denver's dry periods. Ready-to-use formula eliminates mixing requirements for busy gardeners. Works exceptionally well for overwintering peppers indoors during Colorado's harsh winters. Contains beneficial microorganisms that support healthy root development and nutrient uptake.

Price: $11.99 → $17.99

Jiffy 7C Coir Pellets 42mm Seed Starting Supplies

https://www.amazon.com/Jiffy-Peat-Pellets-Starting-Supplies/dp/B01MUAGZXJ

Compressed coir pellets expand to create perfect seed starting environment for pepper germination. Biodegradable mesh allows direct transplanting without root disturbance, critical for pepper establishment success. Optimal air-to-water ratio prevents damping-off diseases common in Denver's variable spring conditions. pH-neutral coir provides excellent drainage while maintaining consistent moisture for reliable germination. Eliminates transplant shock by allowing seedlings to develop undisturbed root systems. Perfect size for pepper seeds and early seedling development before transplanting to larger containers or garden beds.

Price: $7.99 → $14.99

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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Written By

Dr. Sarah Green

Sarah earned her doctorate in plant biology and spent time working in botanical garden education before transitioning to freelance writing and consulting. Now based in Portland, Oregon, she teaches plant identification workshops at local community centers and maintains a modest collection of over 60 houseplants in her small apartment. Sarah specializes in helping beginners understand plant science without the jargon—her approach focuses on practical observation over theory. She's killed her fair share of fiddle leaf figs and finally cracked the code on keeping them alive.