Container gardens

August 7, 2012 1:26 PM

Is coarse sand a cheap alternative to perlite, coconut coir or vermiculite when you want to use it in container garden?

I usually mix peat moss and compost in my container garden. This mix compresses by the end of the season. Is there a less expensive material that would work better?

posted by boby to home & garden (8 answers total)

No. Those other ingredients are mainly there to increase water retention, which is important in container gardening. Sharp sand (or better still, grit) will improve drainage, which is kind of the opposite; it's useful for cuttings or other purposes where there's a danger of plant material rotting due to waterlogging.
posted by pipeski at 1:40 PM on August 7, 2012 [2 favorites]

I might be off-base here but it stands to reason that you might be able to use pine straw or some other fairly neutral, small-piece mulch to bulk out the soil, improve aeration, and slow decomposition without affecting water retention as much as sand or grit. I *think* it's quite cheap and would be unlikely to harm your plants. Hopefully someone else will know better.
posted by Scientist at 2:18 PM on August 7, 2012 [1 favorite]

Those things you listed are what you want to use , not sand.
They not only retain water, but allow expansion in the soil to help promote root growth by adding space for air as well.
posted by handbanana at 2:22 PM on August 7, 2012

Those other ingredients are mainly there to increase water retention, which is important in container gardening.

This is actually wrong. Perlite and vermiculite, in particular, aren't great for water retention. They are mainly there to make for a light and airy soil, and to resist soil compaction. That is something important for root development. Coarse sand will not help with that, but there are other things, like leaf mold, that will. Coconut coir, in my experience, goes a long way.
posted by OmieWise at 3:10 PM on August 7, 2012 [2 favorites]

Shredded expanded polystyrene packaging is inert and has many if the structural properties of vermiculite. It has no water retention at all though. Chopped packing peanuts is another option.
posted by cromagnon at 4:22 PM on August 7, 2012

Perlite and vermiculite, in particular, aren't great for water retention.


This is actually half-wrong. Vermiculite does help retain water.
posted by ecourbanist at 9:33 PM on August 7, 2012

Some sort of bark mulch?
I use fir fines in a lot of soil mixes, mostly with mushroom compost.
Good to bulk up soil, and improve aeration.
posted by St. Sorryass at 2:04 AM on August 8, 2012

Thanks for all the advice. I think I'll give coconut coir a try for a few containers next year. It seems to last the longest and be the least expensive by volume.
posted by boby at 5:30 AM on August 8, 2012