I just put together a quick and easy strawbale cold frame to grow late winter/early spring greens. It took about 30 minutes from start to finish.
Step 1. Gather materials: straw bales and a cover. Schlepping strawbales from around the farm was the most labor intensive part of this project. I had enough extra bales lying around, but to purchase them would add about $5 a bale to the cost of the project. Sometimes you can get rained on bales for less than perfect new bales. I didn’t have any old windows lying around (just wait till I get rid of that sliding glass door!) so I used a sheet of 6 mil plastic (25 feet by 10 or 12). This cost $20 at the local big box store.
Step 2. Prepare the soil. I wanted my cold frame not too far from the house and so chose a bed that had been seeded to winter rye in the fall. I chopped up the rye, added a bucket of chicken manure compost, and smoothed the soil with a rake.
Step 3. Arrange the bales. You can see the C shape I used to arrange the bales in the photo. I do not put a fourth strawbale “wall” up because the winter sun is low, and I don’t want additional shade in the front of the growing area. Since I was using plastic sheeting as my cover, I simply let that slope down from the edges of the bales. I set my bales “on edge” so that my walls are higher.
Some people make a cube of straw bales and put an old window on top. This will create a deep frame. To minimize shade you can add crumpled newspaper or mulch or soil on the bottom to third way up the bale, then add 8 inches or so of soil. Make sure you leave enough room on top so the plants don’t hit the glass.
4. Shape the beds and plant. I created a long furrow lengthwise down the middle of the bed for irrigating when the greens are larger. I created small 1 inch trenches parallel to the irrigation trench for planting the seeds. I watered the bed thoroughly with a hose, then planted my seeds, noting in my journal what I planted where. The larger greens I planted in the back next to the straw bale and in the front I seeded mesclun which I will harvest when still small. This way I don’t have to worry about the plastic sheeting squashing larger greens in the front of the bed. Since I had extra row cover lying around, I covered the bed with that and secured with some old rebar.
5. Cover the cold frame. I tucked the plastic inside the twine at the back of the strawbale (see photo). You could also tuck the plastic under the strawbale or use clips to attach it to the twine. We have very strong spring winds here so I put additional rocks on top of the bale to weigh down the plastic. I tucked the plastic under the bales at the edges. In the front, I tucked the plastic under the railroad tie and added a t-post across the length of it for good measure.
The next day we got quite a bit of rain, so I pulled back the plastic so the soil could get watered. The plastic goes back on at night. When your greens start growing, be sure to monitor the temperature inside your cold frame and open it up so you don’t cook your new greens.
Now I have a nice toasty secure mini greenhouse to grow my spring greens. You can also do this in the winter to extend your fall vegetables. I like these strawbale mini hoophouse/cold frames because I can move them around wherever I have open space. I don’t need to commit to a permanent hoop house location or use lumber and concrete or PVC to build it. I can simply compost the bales or use them as mulch when they decompose. The downside of this type of cold frame as opposed to a larger hoophouse is that you can’t walk in it, so if you make it very deep, managing the glass or plastic can be unwieldy.
Happy planting! – Jen