When to Plant Scallions in Colorado (2026 Guide)
Planting scallions in Colorado can provide gardeners with a bountiful harvest throughout the growing season. With their versatility and ease of cultivation, scallions, also known as green onions, can thrive in various locations across the state. Ensuring you plant them at the right time is crucial, especially when considering Colorado's distinct frost dates, such as the median last spring frost on May 5 for Zone 5b.
Knowing when to plant scallions helps maximize your gardening efforts and takes advantage of Colorado's 149- to 174-day frost-free growing seasons, depending on your zone. For example, if you're gardening in a Zone 6a area like Grand Junction, your median last spring frost is as early as April 25, allowing for an earlier planting compared to other regions. This flower can be sown directly outdoors or started indoors at varying times according to your local frost dates.
As you plan for your scallion garden, remember that they can be sown every 3–4 weeks for a continuous supply. Incorporating timeless gardening practices alongside the specific challenges that face Colorado's unique climates will set you up for a fruitful scallion harvest from late spring through fall. With the right timing and care, you can enjoy delicious scallions well into the gardening season, whether you're growing them in Denver or Colorado Springs.
Planting Schedule by USDA Zone in Colorado
| Zone | Indoor start | Transplant out | Direct sow | Harvest |
|---|---|---|---|---|
| Zone 5b | Start February 15 – March 1, ~6–8 weeks before May 5 | Transplant outdoors from May 6 – May 20, after the last frost | Direct sow from May 6 – July 1 for continuous crops | Harvest between June 15 – October 1, just before the first fall frost |
| Zone 5a | Start March 1 – March 15, ~6–8 weeks before May 17 | Transplant outdoors from May 18 – June 1, after the last frost | Direct sow from May 18 – July 2 for a steady supply | Harvest between June 15 – September 27, just before the first fall frost |
| Zone 6a | Start March 1 – March 15, ~6–8 weeks before April 25 | Transplant outdoors from April 26 – May 10, after the last frost | Direct sow from April 26 – July 10 for ongoing crops | Harvest from June 15 – October 16, just before the first fall frost |
Scallions Planting Windows in Colorado
- Indoor start: For scallions in Colorado, the indoor starting window is February 15 to March 15, depending on frost dates.
- Transplant outdoors: Transplanting outdoors should occur from May 6 to June 1 in Zone 5b, while Zones 5a and 6a provide different timelines.
- Harvest: The scallion harvest window in Colorado stretches from June 15 to October 16 based on local frost dates.
Common Mistakes Growing Scallions in Colorado
- One common mistake is delaying the start of indoor scallions in Colorado, particularly in Zone 5a and 5b, where you may miss the optimal planting window if you wait too long into March.
- Another frequent error involves planting scallions too close to frost-sensitive crops. While scallions tolerate light frost, it's best to ensure neighboring plants can withstand the Colorado climate for the growing season.
- Sowing scallions too early can lead to damaged seedlings due to late frosts. It's essential to respect frost dates in your zone and avoid starting too soon, especially in mountainous regions of Colorado.
- Many gardeners forget that scallions can be planted directly in the garden after the last frost, resulting in over-crowding in pots and missed outdoor growing opportunities throughout Colorado's warm growing season.
- Ignoring the benefits of succession planting is a common mistake in Colorado. Planting scallions in regular intervals every few weeks can ensure a continuous harvest, which is often overlooked by novice gardeners.
Frequently Asked Questions
What if I'm in a cold pocket of Colorado?
If you're in a cold pocket, consider starting your scallions indoors about a week earlier than the recommended dates to ensure they are ready to be transplanted outdoors once the frost threat has passed.
Can I still plant scallions in May?
Yes, if gardening in Colorado, once you pass your respective last frost date, May is an excellent time to directly sow scallions for a summer-fall harvest.
How do I know when to harvest my scallions?
You can start harvesting your scallions when they're about 6–8 inches tall, which is usually between June 15 to October 1, depending on your planting timeline.
Are scallions frost-tolerant?
Yes, scallions can tolerate light frosts with minimal damage. However, if it gets very cold (below 25°F), consider using row covers to protect them and extend your harvest season.
What soil conditions do scallions prefer?
Scallions thrive in well-draining, nutrient-rich soil. Considering Colorado's varied soil types, amend your garden beds with organic matter such as compost to ensure optimal growth.
Keep Learning
City guides in Colorado
Other crops in Colorado
Typical fall sowing window for Scallions in Colorado: July 16 – August 6.