Cold Frames on the Cheap: Keep Greens Alive

I lost a whole flat of spinach last November because I figured it would probably be fine. It was not fine. We got a surprise hard freeze, I had done nothing to protect anything, and by morning the spinach looked like it had just completely given up on life. Every last leaf.

So this year I actually thought ahead. Mostly.

The good news is that keeping greens alive through a PNW winter doesn’t require a fancy greenhouse or a heated growing space. It requires a few dollars and a willingness to look slightly unhinged in your backyard.

What You’re Actually Protecting Against

Here in Redmond, a true killing freeze is less common than the shoulder-season stuff. Those nights that dip into the high 20s or low 30s right when your kale and spinach and lettuce are doing great. Most hardy greens can handle a light frost. It’s the repeated hard freezes without any protection that really hurt them. You’re not trying to build a tropical paradise out there. You’re just buying a few degrees.

Row Cover: The Lazy Option (I Mean That as a Compliment)

If I had to pick one thing that earns its keep out here, it’s floating row cover. The lightweight stuff, around 0.5 oz, adds a couple degrees of protection and lets in enough light and rain that you basically just drape it over your plants and forget about it. The heavier 1.5 oz version adds closer to 6-8 degrees of protection, which actually matters when November decides to be dramatic.

I picked up a roll at Sky Nursery a few years ago and I’m still using it. Reusable, washable, cheap enough that I bought a second roll without feeling bad about it. Which, if you think about it, is the highest praise I know how to give a garden product.

You can hold it down with rocks, boards, soil staples, or in my case whatever random heavy thing is sitting near the raised bed. Last week that was a bag of perlite and a ceramic frog my youngest painted at school. Whatever works.

Cold Frames From Stuff You Already Have

Row cover is great but a cold frame is better for the really cold nights. And here’s the thing: you do not need to buy a cold frame kit. Those run $40-$80 at the garden center and I refuse.

The classic setup is old windows laid over a wooden box. I built mine out of scrap 2x8s from a fence project and two storm windows I found at Earthwise Salvage for $3.47 each. Total out of pocket was under $8.00. It’s crooked and one of the windows has a crack in the corner but it works exactly as well as an expensive one.

No old windows? A shower door works. A sliding glass door panel works. Even a clear plastic storage bin turned upside down over a single plant works in a pinch. The goal is just to trap some ground heat and block the wind. The plants do not care what it looks like. (My wife might have a different opinion but she’s learned to pick her battles.)

The Jug Trick for Individual Plants

For protecting one-off plants, I save gallon milk jugs and cut the bottoms off. Poke a few holes in the sides for airflow, set them over small plants on cold nights, take them off in the morning when temps come back up. Free, which is the right price. I’ve used the same four jugs for three winters now. The caps double as little vents if you leave them off on warmer nights.

I’ll be honest, I forgot to take them off one morning and came home to some very sad, cooked-looking seedlings because the sun heated things up way too fast. So. Lesson learned: these are for nights only unless it’s going to stay cold all day.

What’s Worth Growing Right Now

Even with protection, you want to be realistic about what you’re asking your plants to do in November. Kale, spinach, mâche, arugula, and overwintering varieties of lettuce are your best friends right now. They’re cold-tolerant enough that a little protection goes a long way. Trying to keep basil alive under a row cover in November is, let’s say, an exercise in expensive disappointment. I say this from experience. Recent experience.

Hardy greens under even a cheap cold frame can handle temps down into the low 20s most nights. That covers almost everything we get here in zone 8b until the real cold snaps show up.

The Short Version

Row cover for the easy nights. Cold frame from scrap wood and old windows for the hard ones. Milk jugs for the stragglers. Spend maybe $10 total and keep eating out of the garden through February.

Lettuce not give up on the garden just because it’s November. (I’m not sorry.)

Photo by Cody Nicoll on Unsplash