When to Plant Broccoli in Fort Collins, CO
Published: April 21, 2026
Broccoli Planting Dates for Fort Collins, CO
| Start seeds indoors | February 16–23 |
| Last frost (average) | March 30 |
| Transplant outdoors | March 2–12 |
| Direct sow outdoors | March 2–12 |
| Minimum soil temperature | 40°F |
| Expect first harvest | May 1 – May 21 |
| Fall crop planting | August 23–September 2 |
| Fall crop harvest | October 22 |
| First fall frost (average) | November 1 |
Best Broccoli Varieties for Fort Collins, CO
For Zone 6a Fort Collins, the best-performing broccoli varieties are Belstar, Green Comet, and Arcadia — all widely adapted, disease-resistant varieties proven across the transition zone. Marathon is a good alternative where disease resistance matters most, especially in humid summers. These varieties are typically stocked by local nurseries and are the safest bets for gardeners new to broccoli in Fort Collins.
Growing Broccoli in Fort Collins
Fort Collins sits in Zone 6a, with an average last frost of March 30 and first fall frost around November 1 — giving a 216-day frost-free growing season. Cool-season crops like broccoli benefit from Fort Collins's cooler spring and fall windows, when temperatures stay in the 55–75°F sweet spot that produces the best flavor and least bolting.
Fort Collins's moderate climate supports broccoli on the standard transplant calendar with minimal special accommodation. Succession planting — sowing fresh seeds or setting new transplants every 2–3 weeks through spring — stretches the harvest window and gives you a backup crop if pests hit the first planting.
Fort Collins's well-draining loam soils are among the best for broccoli growing — focus on annual organic matter additions (2 to 3 inches of compost) and consistent moisture during drier months. Water broccoli at 1.5 inches per week; loam holds moisture evenly without the drought-crack cycle of heavy clay or the rapid-drain losses of pure sand.
Broccoli Calendar for Fort Collins
| Month | Task |
|---|---|
| February | Start seeds indoors under grow lights |
| March | Transplant outdoors into warm soil |
| May | Expect first harvest window to open |
| August | Start fall crop — transplants or direct sow |
| November | First fall frost — harvest remaining, end of outdoor season |
Broccoli Tips for Fort Collins Gardeners
- •For spring: start indoors 6 weeks before last frost and transplant outdoors 4 weeks before last frost.
- •For fall: start indoors in summer — count 10 weeks back from your first fall frost date.
- •Succession plant broccoli in Fort Collins every 2–3 weeks through spring to extend the harvest window into summer.
Common Broccoli Pests in Fort Collins
- •Cabbage Worm — peaks July in Zone 6a (active May–September); green caterpillars on brassicas; apply Bt spray or use row covers.
- •Cabbage Looper — peaks July in Zone 6a (active May–September); loop-walking green caterpillars; Bt spray works well.
- •Aphids — peaks July in Zone 6a (active May–September); clusters on leaf undersides; blast with a strong water spray or apply neem oil.
Check plants every 2–3 days during peak season — early intervention prevents most infestations from becoming serious.
What to Plant with Broccoli in Fort Collins
In Fort Collins's moderate climate, Onion and Garlic are the most beneficial plants to grow alongside broccoli. Onion deters carrot fly, aphids, and several root-zone pests through sulfur compounds. Keep broccoli away from Tomato — it competes for nutrients or shares pest pressure.
Frequently Asked Questions
When should I plant broccoli in Fort Collins, CO?
In Fort Collins (Zone 6a), start broccoli seeds indoors around February 16–23 and transplant outdoors around March 2–12. The city's average last frost of March 30 is the anchor date — count 6 weeks back for seed starting and 4 weeks back for transplanting.
What zone is Fort Collins, CO for broccoli growing?
Fort Collins is USDA Zone 6a. For broccoli, this means a frost-free growing season of roughly 31 weeks running from March 30 to November 1. Cool-season crops like broccoli thrive in this zone with both spring and fall planting windows available.
When is broccoli harvest season in Fort Collins?
Expect the first broccoli harvest in Fort Collins around May 1, with harvest continuing through May 21. This is based on 60–80 days from transplant or direct sow. A fall crop planted August 23–September 2 adds a second harvest around October 22.
How long does it take to grow broccoli in Fort Collins, CO?
From transplant or direct sow to first harvest, broccoli takes 60–80 days in Fort Collins's climate. Based on a typical planting date of March 2–12, expect your first harvest around May 1. Fort Collins's Zone 6a transition-zone climate produces maturity times right in the middle of the stated range.
What soil does broccoli need in Fort Collins?
Fort Collins's loam soil is near-ideal for broccoli. Work in 2–3 inches of compost before planting to boost organic matter and nutrient content. Minimal amendment is needed beyond that — loam holds moisture evenly without the drought-crack cycle of clay or the nutrient-loss issues of sandy soil.