Organic Gardening – Strawbale Gardens and Coldframes

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My new favorite gardening material is the strawbale. Strawbales are used for people housing, animal bedding, animal housing, mulch and now in an even bigger way in the garden.

The strawbales used to build homes have high insulating properties. Aside from their thickness, the air spaces between the pieces of straw keep heat from transferring in or out. Air is a great insulator.

Strawbale coldframe

Photo: Grady James

My own strawbale coldframes for gardening

I used the insulating properties of strawbales to build a coldframe this year. I bought 10 strawbales and lined them up to make a rectangle. I dug out all the grass clumps and weeds that were inside. I thought about lining it with weed mat, but I don’t seem to be having a huge problem with weeds growing. That might change once I start watering more and temperatures rise, but for now, bare dirt is fine.

The interior dimensions are about 6’ wide by 12’ long. This was the perfect size to cover with several recycled doors from the Habitat for Humanity ReStore.

I had seedlings growing in the passive solar greenhouse that is attached to my house. I had to move them out to make room for more (I am selling garden starts this year). Once the coldframe was finished, I put a hi-lo thermometer inside for a few nights to see what the overnight temperatures would be. Generally, they were about 10-15 degrees above the outside temperature. Daytime readings hovered between 65-70.

At first I put plants out just during the day, bringing them back in at night. I watched the weather (like every good gardener should do!), and when I thought the coldframe could hold an overnight temperature of about 45, I left the plants outside.

I covered the top with two layers of greenhouse bubble wrap I bought from FarmTek and many blankets that my daughters left behind when they went to college. The whole thing was topped with a tarp held down by pieces of lumber. I waited to remove the covers until the sun was high enough to warm it up.

It’s been successful! The plants are thriving in the heat of the day! I adjust the glass tops as need be to keep it from getting too hot or cooling off too fast. And they are hardy enough to handle 45 degrees overnight, which is our usual summertime temperature. You can see a photo of it on my strawbale gardening Pinterest board.

How do strawbales work as gardening containers?

This spring, two friends mentioned they want to use strawbales as containers for planting. I didn’t quite get it until one of them said you dig out some of the top, add soil and plant in it. She is going to use a row of them as a barrier between the parking area of her bakery and the outside seating section.

Then I came across this article about a strawbale gardening guru, Joel Karsten. He uses strawbales as containers, like my friend said. The idea is that once a bale begins to decompose from water and fertilizer (the simple preparation steps!), it becomes the nutrients the plant needs. Decomposition also heats up the inside of the bale allowing you to plant a little earlier. You can cover it with plastic for chilly nights.

To the top of the strawbale (keep the strings on the sides), add a bit of amended topsoil and fertilizer, and water it well. Karsten is not an organic gardener, but he does give recommendations for organic fertilizer. Run a soaker hose along the top of the bale and add some posts at each end to run twine for a trellis. When the bale is warm (it just takes a few days), add your transplants. Done! No mulching, no sprinklers, no bending. See my Pinterest board for images of Karsten’s work.

Strawbale gardening is a great way to grow something when you have poor soil, don’t want to do a lot of bending, live in the city with minimal space or have arid conditions. I don’t know how long you can use one bale, but it can be used for mulch or compost when it’s worn out. It surely is recycling!

I am going to grow my warm weather vegetables in strawbales this year on the warm side of the house – tomatoes, peppers, winter squash, zucchini, cabbage and sweet potatoes. Wow, what an experiment! I will keep you posted on my strawbale gardening adventures!

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Nan Fischer

Nan Fischer has been living and building green for over 35 years. Nan’s emphasis on the BuildDirect blog is about how to make your dollar stretch further, while also moving toward a more sustainable lifestyle, as well as upcoming and existing technology to help us live in an ecologically-friendly way. Nan also authors posts on the website of her seed business, sweetly seeds.