Yes! You Can Start Seeds in a Zone 6a Coldframe in the Middle of Winter

In researching winter coldframe growing, I found not many gardeners start cold frame plants in the middle of winter. Reasons given are: seeds will rot in cold, wet soil, not the natural sprouting time for seeds, tender small plants will freeze.

While all of the above are accurate statements, I'm in zone 6a, where winters are mostly forgiving. The average weekly temps can range from low teens to high 50Fs and above. Typically, Jan and Feb bring a couple weeks of freezing weather when cold frame plants need extra protection, but there are milder days through much of the winter months.

Here are the growing assists I've given my cold frame plants:
1. Good composty, humus rich soil prepped two months before planting.
2. Seeds chosen for sowing are cold tolerant, hardy plants that prefer cool grow conditions.
3. Interior (and exterior) of wooden coldframe is painted with moisture resistant, light reflective white enamel paint.
4. Solid foil faced insulation sheet along the interior frame walls for sunlight reflection/cold air barrier.
5. A light bulb hanging in the interior - for heat and light on cold, cloudy days.
6. Milk jugs filled with dark color water for passive heat radiation.
7. Soft adhesive faced, foam insulation added along cold frame top edge to prevent cold air from entering the frame along the closed glass lid.
8. When outdoor temps drop below 40 with cloudy skies, the light bulb is turned on, the cold frame glass lid is covered with cardboard sheets and an old sleeping bag - all topped by heavy black plastic sheeting.
9. Attention to: adequate watering - venting on warm sunny days, closing lid before outside temps drop below 40F.
10. Dilute liquid fertilization tri-weekly after sprouts are 3-4" tall.

Two points of this grow-box that I will change up:
Install a height movable, 4 ft long narrow profile grow light to prevent excessive sprout reaching. **Note: the sprouts are sturdy due to cooler growing temperature.
Add more water jugs along back of frame interior.



Seed/Plant List:
Broccoli Raab
Cabbage - Pak Choy, Shang Hai
Claytonia
Herbs - Borage, Chervil, Coriander
Greens - Arugula, Blk Seed Simpson, Mache Vit, Rouge d'Hiver, Tatsoi, Wabasina Mustard
Kale - Black Magic
Kale - Lacinato
Onions, Tokyo Bunching
Radish - Cherry Belle
Spinach - Space F1
Transplants: Garden Sage, Italian Oregano, Celery, Leeks