When to Plant in Colorado

Colorado's high altitude and arid climate create unique gardening challenges — and opportunities. The Front Range cities like Denver sit at over 5,000 feet, which means intense sun, cool nights, and a risk of frost well into May.

Water-wise gardening is essential in Colorado. The state receives relatively little rainfall, and most of it comes as afternoon thunderstorms in summer. Drip irrigation, mulching, and choosing drought-adapted varieties are key strategies for success.

Common Mistakes

Underestimating altitude — even Denver's mile-high elevation means cooler nights and more intense UV than sea-level gardens.
Not protecting plants from hail — Colorado's summer thunderstorms can destroy crops in minutes; hail cloth helps.
Overwatering — Colorado's dry air and fast-draining soils trick gardeners into overwatering, which can cause root rot.
Planting too early — the Front Range can get snow through Mother's Day, and mountain towns even later.

FAQ

What is the last frost date?

The last frost date is the typical date in spring when your area has its final frost. After this date, it's generally safe to plant warm-season crops outdoors.

When should I start tomatoes indoors in Colorado?

Start tomato seeds indoors about 6–8 weeks before your last frost date. In the Denver area, that's typically mid to late March. Mountain areas may need to start in April.

Can I plant before the last frost?

Yes — cool-season crops like lettuce, peas, spinach, and broccoli can handle light frost and should be planted 4–6 weeks before your last frost date.

Why does timing vary so much within Colorado?

Altitude is the main factor. Denver at 5,280 feet has a different season than mountain towns at 8,000-10,000 feet. The Western Slope and eastern plains also differ significantly.

What if I live in a frost-free area?

Colorado doesn't have frost-free areas. Even the Grand Junction area and southeastern plains have winter frosts. Enter your zip code in the app for your exact frost dates.

How does Plan My Garden create my schedule?

You enter your zip code, and we look up your local frost dates. Then based on the crops you pick, we calculate when to start seeds, transplant, and harvest — personalized to your location.