Colorado · zones 5a–7a
When to plant garlic in Colorado.
Colorado's window for garlic runs on the fall side of the season. A second, fall sowing fits Sep 29 to Oct 14. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Garlic dates for a typical Colorado season.
Fall round
Sep 29 to Oct 14
Counted back from the ~Sep 29 first frost.
Harvest
~240 days later
~0.2 lb per plant over ~1 weeks.
Colorado spans more than one climate: Zone 6 is the most common zone, but the state runs 5a to 7a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
In Colorado: watch for
The pests that find garlic here.
The short season here, about 143 frost-free days, keeps garlic in front of onion thrips only briefly. One early row cover usually carries a planting through the worst of it.
Silvery streaks and curled leaf tips in hot spells.
Organic fix: Insecticidal soap or neem; hang sticky traps.
Seedlings wilt; white maggots in the bulb base.
Organic fix: Float a row cover over the row; rotate beds each year.
Pale patches with fuzzy gray growth in damp weather.
Organic fix: Space for airflow, water early in the day, spray neem.
White rot
Yellowing and dieback, then wilt; fluffy white mold at the bulb base and roots so rotted the plant lifts straight out.
Organic fix: No cure once it is in the soil. Plant clean stock, never follow onions with onions, and keep infested soil off tools and boots.
Your season math: Colorado gives garlic about 143 frost-free days, and it needs roughly 240 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting garlic in Colorado: questions
When should I plant garlic in Colorado?+
Colorado's window for garlic is in fall: Sep 29 to Oct 14, keyed to the first fall frost around Sep 29.
What USDA zone is Colorado?+
Colorado spans zones 5a–7a, mostly zone 6. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many garlic plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.