soil mix for square foot boxes

Today I bought the materials to make 3 4'x4' raised boxes for my backyard. The info at Square Foot Gardening says the mix should be 1/3 compost, 1/3 peat moss and 1/3 vermiculite. But, when I was up at Gesthemene today, they didn't have any vermiculite, saying it was "banned" (I'm assuming they were thinking of the asbestos contamination thing from a few years ago) and only had small bags of perlite, which I assume would cost a bundle for 9-10 cu/ft I'd need.

So my questions are:

- is vermiculite still available and if not, where can I get large bags of perlite ?
- short of getting either of those, anyone have any suggestions for another mix ?

I'd not heard of the asbestos, so I did a search to find out what it was about.

This site might help you: http://www.vermiculite.com/

I hope you find it; I was going to look for some this season myself.

tem wrote:- is vermiculite still available and if not, where can I get large bags of perlite ?

Yes, but I get it in KC, so the source may not be of much help.

I did get a fine grain vermiculite at Lowe's for sprouting seeds, but only found the coarse grain at a local nursery.

Perlite and horticultural vermiculite are more or less interchangeable for most horticultural purposes. Note that horticultural vermiculite absorbs water very well while vermiculite for insulation is treated to resist water. Few places seem to carry larger bags of either as they are used mostly for mixing your own growing media while garden centers would rather sell premixed stuff at higher prices. Perlite used as a lightweight aggregate in plaster or interior concrete is the same as used in gardening.

The four cubic foot bag of perlite that I am working on was purchased at Sid's Greenhouse in Palos Hills several years ago. Most real greenhouses use a fair amount although polystyrene pellets have replaced perlite in many bedding plant growing operations. Unfortunately, most local greenhouses don't really grow a lot of their own plants any more.

Edit to add: Perlite and vermiculite dust can be nasty, so wear one of those paper dust masks when dumping or mixing.

well, after calling about 10 different places, I found that Anton's in Evanston has the 4 cu/ft bags of vermiculite for $18 so I'll be heading up there on Saturday for 4 of those plus 16 cu/ft of compost and 16 cu/ft of peat moss. They also have a 10% of coupon on their website so that will cut down on the cost as well.

As for the compost, they have one that's $2.75 for a 1.5 cu/ft bag that I'm assuming is the 10% manure (or mah-nuah as George Costanza would say). They also have a mushroom compost for $3 cu/ft. But, does the "100%" manure places like Gethsemane for $6.99/per make a difference ? I've also heard conflicting things about mushroom compost, which I could get at Lake Street Landscaping Supply for $1.23/per (in cu/yard quantities). I'm waiting to hear back from them re: a custom mix of compost, peat and their own additive that would probably be about $2.25-$2.50/per cu/ft.

Ekreider ... opinions ?

thanks !

I make my own compost so am not the best source regarding purchasing the stuff. I do collect bags of other peoples' leaves in the alley in the fall to augment my own supply.

Do not substitute composted manure for compost making up a third of your mix. The nutrient level (and smell) will be way too high. Treat composted manure as fertilizer.

Everything I have seen about mushroom compost is that it is a pretty good source of organic matter but has little nutrient value because the mushrooms pretty much use up the nutrients. Five to ten percent composted manure with the rest mushroom compost could be a good way to approximate good compost.

ekreider wrote:Do not substitute composted manure for compost making up a third of your mix. The nutrient level (and smell) will be way too high. Treat composted manure as fertilizer.

Everything I have seen about mushroom compost is that it is a pretty good source of organic matter but has little nutrient value because the mushrooms pretty much use up the nutrients. Five to ten percent composted manure with the rest mushroom compost could be a good way to approximate good compost.

so maybe I should just get the 10% manure compost, which has, I assume, 90% other organic matter ?

who knew s*** would be so confusing. Perhaps I should just get myself a case of Activia and go to town

When I made Mel's mix, I used 1 part manure, 1 part Duck Doo (available at the place I got the vermiculite), 1 part mushroom compost, and 2 parts a blend (from the same place) which is about 70% cotton burr, but also has 5 or 6 other things...alfalfa is the only one I can remember off-hand.

heh heh ... strange how these things happen ..

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