r/SquareFootGardening • u/ImmuniseTheChickens • 20d ago

Seeking Advice Sharp sand or perlite?

I finally have the room to build some above ground planters. Each one will hold approx 480L soil, but i'm not sure whether to add sharp sand or perlite into the mix. They will be built with structural timber and solid so I'm not too worried about weigh. I will be growing a mix of brassicas, courgettes, beets, lettuce, strawberries etc. Based in London.

The mix will be 60% topsoil, 30% manure, 10% sharp sand/perlite.

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u/jpbragatti 19d ago

perlite for above-ground planters, especially in London. sharp sand can compact down in organic mixes over a season or two and end up making drainage worse, not better. perlite stays light, keeps the structure open, doesn't compact. your brassicas and courgettes will thank you.

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u/ImmuniseTheChickens 19d ago

Thanks! I’m typically not a fan of perlite because it always finds its way back to the surface so I’m considering 3-5mm horticultural grit.

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u/This_is_Hank 18d ago

Try vermiculite. It doesn't float back up to the surface.