When to Plant in Denver, CO

Denver sits at 5,280 feet elevation — Zone 6a with a typical last frost around May 9. The mile-high altitude means intense UV rays, cool nights even in summer, and a risk of late frosts well into May. Afternoon thunderstorms and occasional hail are summer hazards.

Denver gardeners work with a growing season of roughly 150–160 days. Starting seeds indoors is essential for tomatoes and peppers, and choosing short-season varieties helps ensure harvest before the first fall frost around October 1.

FAQ

When is the last frost date in Denver, CO?

Denver's average last frost date is around May 9. Start tomato and pepper seeds indoors in mid-March and don't transplant outdoors until after early May.

How does Denver's altitude affect gardening?

The 5,280-foot elevation means intense UV rays that can scorch plants, cool nights that slow warm-season crops, and lower atmospheric pressure that changes water needs. Use sunscreen on new transplants!

What about hail in Denver?

Denver's summer thunderstorms can bring damaging hail. Hail cloth or shade cloth provides protection. Keep old sheets or row covers handy to throw over plants quickly when storms approach.

What grows best in Denver?

Short-season tomatoes, peppers, squash, and beans do well in summer. Fall is excellent for kale, lettuce, broccoli, and carrots. Potatoes and root vegetables thrive in Denver's cool soil.

How does Plan My Garden help Denver gardeners?

Enter your Denver zip code and we'll generate planting dates calibrated to the Front Range's altitude, frost dates, and short growing season.

Frost dates for Denver ZIP codes

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