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Landscape Gardening

Filtration for wooden planters

I have recently built 2 wooden planters 400cm x 50cm @ 50cm deep.
My question is I don't want to fill them with soil I've seen these stones at the bottom of a friends planter there like little hollow breeze block stones really light and take up room as well as acting as a filtration for water so my question is does anyone know what they are? And where I can get them from or anything else I could use instead?


1 Answer from a MyBuilder Landscape Gardener

HI Tom - If you want to improve the drainage in the planter it's best to make the potting mix coarser, rather than rely on a bottom layer of rocks for filtration. The coarseness of the mix and gravity's pull on the water aren't changed any by adding extra rocky pieces at the bottom. Use chunks of bark or another suitable organic product evenly mixed throughout the potting mix rather than relying on bottom layer of gravel. The suggestion that a bottom layer of rocks aids with drainage isn't correct as all it does is pushes any saturated layers (water that is held by the finer potting mix particles, which the roots rely on for nutrient uptake) upwards through the mix.


Answered 18th Aug 2018

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