When to Plant Broccoli in Colorado

Growing Broccoli in Colorado: Complete Guide

Broccoli (Brassica oleracea var. italica) is a warm-season crop that needs a head start indoors before Colorado's last frost. Most Colorado gardeners begin seeds indoors around Monday, March 9, 2026 and move transplants outside around Monday, April 20, 2026, after the risk of frost has passed.

Because Colorado stretches across 7 USDA hardiness zones (4a, 4b, 5a, 5b, 6a, 6b, 7a), planting windows can shift by as much as six to eight weeks from one end of the state to the other. Gardeners in the warmer southern zones can start earlier, while those in cooler northern zones should wait until the zone table above shows their last frost has passed.

With 60 days to maturity, Broccoli needs the indoor head start that Colorado's growing season requires. Starting indoors ensures you have strong transplants ready the moment outdoor conditions are right.

Broccoli requires full sun (6 hours) and regular (1-1.5 inches/week) moisture. Most of Colorado receives adequate sunlight during the growing season, though gardeners in humid eastern regions should watch for fungal issues and ensure good air circulation.

For the most precise planting dates tailored to your exact location, enter your ZIP code on our planting calendar or use the zone table above to find the schedule for your area of Colorado.