I saved my garden plastic bags and used them when I screened pine bark mulch to get a gritty size suitable for opening up a potting mix so it holds more air and less water. The too-big pieces went into bags for mulch or re-chopping. The finest stuff was saved in bags for lightening raised bed (clay) soil when I dug it up every few years.
But now I use most of my saved bags for lining raised beds' walls to slow down evaporation. These pictures are from before I started doing that, and I had to water some of the beds daily.
(That is a downside of using concrete paving stones stood upright as bed walls. The thin concrete wicked water away which then evaporated on the outer surface of the pavers, leaving white salt deposits behind. The cracks between pavers also promoted drainage and evaporation.)
(You can see how much the soil subsided in two years after I amended some clay with a lot of bark and compost and coir and only a little crushed stone. If I had lined those walls with plastic and then let the amended soil subside, you would have seen 6-8 inches of ugly plastic film flapping at the soil surface.)
(Sometimes it seems funny to create raised beds so water can drain OUT of clay soil, then line the walls with plastic so the raised, amended soil
doesn't dry out between waterings! But I can't grow at-grade in clay, and some of my raised, amended beds used to dry out like a seedling in a tiny newspaper pot.)
In one case, I also lined the
bottom of the bed because it sits on top of heather roots and Rhododendron roots. So far that seems to be working (crossed fingers).
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