Cheap and Easy Lasagna Gardening
Bamboo makes for one sexy garden bed. And I love the chop and drop cold composting (biodegredation) in place, however adding the cardboard to the bottom may not always be the best choice if your “compost” added on top has seeds in it like David’s kitchen scraps and almost finished compost might. This is why I prefer the cardboard/paper on top, and planting in holes method where you then add a mulch layer on top, like Morag does here in her forked grass garden.
I will leave you to decide if forking is not digging. Because at the time I write this, 48 downvote people think forking is digging. 🙂
I also know that David’s only renting and so probably doesn’t care how long his bamboo bed lasts, but if others want the bamboo to stick around longer than a couple of years the bamboo needs an environmentally friendly “fixing type” preservation treatment that isn’t affected by rain that is also safe to burn or mulch later on.
Treating wood isn’t always a perfect process as I found with some treated pine I used as a temporary walk way in one of my beds. It’s now covered by a lovely white rot fungi! It’s also covered in dog shit since my brothers dogs, chicken, canary & cat have come to stay…
Here’s an overview of different eco friendly preservation methods.
Traditional options include water leaching where bamboo is submerged in water for months, and smoke treatment is another. Another is transpiration where freshly cut bamboo is sat in a solution like copper sulphate 1:10 parts water, or boric acid and boron, soaked like you would cut flowers. The use of cashew nut shell oil and wood vinegar sound like other options. Any materials you have that don’t break down readily probably have natural oils in them you can extract. Shou-sugi-ban and pine tar may be other options. I’d try a combination and keep any biochar used to make the smoke and wood vinegar, for the garden bed.
In David’s lasagne bed he mentions the salty seaweed he added to the bottom. I’ve read of a farmer here in Australia using a layer of biochar in their orchard to reduce the salinity of soil caused by a saline water aquifer. So maybe a layer of biochar on top of the seaweed might help? It’d also catch and hold any of the nutrients biodegrading and leaching from above!