Fresh Greens in April

Charlie’s harvesting spinach.

Last fall, Charlie built several cold frames for his garden in South Boulder. Cold frames are basic structures which are used to extend your season (with an early start or a later end). With four walls and a glass top, cold frames operate as green houses; heat from the sun becomes trapped in the box to keep plants warm through cold nights. They’re very easy to make. Check out a local used building material source (like the Resource Yard,) to build your own cold frame. Here’s a great guide for building cold frames: http://www.gardengatemagazine.com/main/pdf/coldfram.pdf. But, there’s no need to get too fancy.

While the last three days have been quite hot with intense sun all day long, cold winter nights might still threaten our plants. To protect them, Charlie added those gallon containers to snuggle up with his spinach. Painted black and filled with water, these containers retain heat which they release slowly as cooler temperatures settle in overnight.

Organic Gardening magazine warns cold frame newbies to make sure you don’t bake your plants. According to them, “The temperature inside the cold frame should stay below 75 degrees F for summer plants, below 60 degrees for plants that normally grow in spring and fall. The way to keep temperatures cool inside a cold frame is to lift the lid. A good rule of thumb: when outdoor temperatures are above 40 degrees, prop open the lid 6 inches; when the outdoor temps clear 50 degrees F, remove the lid. Be sure to restore the lid in late afternoon to trap the heat inside for the cool night” (http://www.organicgardening.com/feature/0,7518,s-5-19-106,00.html).

Unfortunately, this spinach has already been baked. Charlie had to pick through the patch to remove scorched leaves. (Scorching seems to be the theme of the week around here.) Despite that, his cold frames have served him well so far. He planted about a month ago and he’s been harvesting spinach for about 2 weeks. That’s a solid 45 days before Brian and I can expect to harvest anything.

As you can see, a good cold frame can be moved. Spinach is frost-tolerant, and hopefully the lowest temperatures are behind us, so Charlie moved the cold frame off his spinach.

If cold frames are considered season extenders, I take this to mean the season has begun!