If you're looking for the easiest, and cheapest, way to propagate your seedlings then you can't go past this primitive coldframe.

Aaron from <a href="http://groovygreen.com/groove/?p=578" target="new" rel="noopener">GroovyGreen</a> recently posted this very simple DIY on putting it together but honestly, I think most people could work it out from the picture.

Simply box together 4 straw bales and stick an old window frame over top. Not really that challenging, is it?

The theory behind the concept is that as the straw begins to decompose it builds up heat which then warms up your propagated material. The window frame allows sunlight into the middle of the bales and also traps the heat from escaping. It's probably not the best idea to start in the middle of summer - but then I guess that's why it's called a coldframe.

Aaron suggests in one of his comments that the inside of the bales could be lined with plastic to give it even more heat but this would only apply in the coldest of climates.

If you plan to construct one of these in your backyard putting aside a day to complete it will be overkill. Five minutes ought to do it....