Winter sowing is letting seeds experience winter outdoors in protected containers so they germinate naturally at the right time.
Winter sowing is a simple seed-starting method where you sow seeds outdoors in winter, usually in recycled containers, and let nature handle the cold stratification, moisture, and timing.
Instead of babying seedlings under grow lights, you create tiny 'mini greenhouses' outside and let them sprout in their own time when conditions are right.
How it works
The container traps warmth like a greenhouse, but still allows natural cold exposure. Seeds germinate at the proper time - no hardening off is needed.
Why gardeners love it (especially in Colorado)
In our climate, it’s especially helpful because spring weather swings wildly. Winter-sown seedlings are already adapted using this method.
Best seeds for winter sowing
When to winter sow in Colorado
January – February
Late February – March
Important note: Place containers where they get sun but won’t blow away. Let snow do its thing - it actually helps!
There are numerous videos on YouTube with visuals and easy step by step instructions.
Instead of babying seedlings under grow lights, you create tiny 'mini greenhouses' outside and let them sprout in their own time when conditions are right.
How it works
- Cut a milk jug (or similar container) almost in half. Leave the cap off (this is important for allowing snow and rain to enter to hydrate the soil and also provides air circulation to prevent mold, fungus, and premature sprouting).
- Add drainage holes in the bottom.
- Fill with I potting mix.
- Sow seeds, label well.
- Tape the jug closed and place outside.
The container traps warmth like a greenhouse, but still allows natural cold exposure. Seeds germinate at the proper time - no hardening off is needed.
Why gardeners love it (especially in Colorado)
- Perfect for seeds that need cold stratification
- No grow lights required
- Strong, sturdy seedlings (not leggy)
- Naturally acclimated to sun and wind
- Takes pressure off indoor space
In our climate, it’s especially helpful because spring weather swings wildly. Winter-sown seedlings are already adapted using this method.
Best seeds for winter sowing
- Perennials (coneflower, penstemon, delphinium, larkspur, bachelor's button, calendula - see full list below)
- Hardy annuals (larkspur, calendula, snapdragon)
- Native plants
- Cold-tolerant vegetables (kale, lettuce, spinach)
- Heat lovers like peppers or tomatoes (those still prefer indoor warmth)
When to winter sow in Colorado
January – February
- Larkspur
- Coneflower
- Penstemon
- Shirley Poppy
- Clarkia
- Pansy
- Moldavian Dragon's Head
- Annual Mallow
- Lacy Phacelia
- Blue Pimpernel
- Poor Man's Orchid
- Scarlet Sage
- Blanket Flower (Gaillardia)
- Black Eyed Susan
Late February – March
- Snapdragons
- Bachelor’s buttons
- Calendula
- Cool-season veggies late March early April
Important note: Place containers where they get sun but won’t blow away. Let snow do its thing - it actually helps!
There are numerous videos on YouTube with visuals and easy step by step instructions.