As I have said in other threads, it is one of the two of the three ingredients I wouldn't skimp on. You can grow your SFG in pure compost, and will probably get good results but the soil texture/moisture retention benefits added by the peat moss (which I believe you can substitute coco-coir for, although not more cheaply, at least in my area) and vermiculite. My own experience, from days before the new SFG and raised beds, where huge chapters of the original SFG book were devoted to preparing, amending, and fertilizing your native soil rather than making a clean, nearly ideal, garden mix. Over the years of that and newer, experience, I found that the vermiculite had the best, and longest lasting, benefits for the soil. Also, unlike the mushroom mix, which apparently gets "used up" and replaced, the vermiculite in your Mel's mix will serve you for many years, as the compost is the only component in constant replacement. I'd really say it's worth springing for the extra 20% by volume you would need (and think of it this way, you are getting to re-use that vermiculite from your mushrooms).
After a lot of searching I found a big, 8cu ft. bag of vermiculite from a local nursery for around $28, which compared decently to the $14 for 4cu ft., "good price" you will see mentioned in the book and here on the forums. I was able to use this to make Mel's Mix for 2 8 inch deep 4x4 boxes. Anyway, that's my two cents, and since your compost contains vermiculite all the time due to the mushroom substrate, you shouldn't have to worry about the normal, slow, decrease in volume of vermiculite as the particles break down, so it should really be a "one time" investment.

:nods: after doing a little more research and reading your comment's I suppose it's worth the investment. I currently only have about a cubic foot's worth of vermiculite left in the barrel so it's about time to order more anyway, might as well bulk up the order for this garden.

wifey's getting a little flustered at the costs of my projects lately (spent last couple weeks completely renovating the front lawn from bermuda to kentucky blue-grass)...

arjo: Since you will be replenishing vermiculite continuously through the composting of your mushroom growing wastes rather than the one-time addition that is typical in establishing a bed "by the book", I'd skip it. For that matter, I wouldn't add coir or peat moss either with that kind of volume of that component coming in every time your replenish where that is also usually just a one-time addition at setup. Because of the unique nature of your compost, after just a few years you are going to have a higher proportion of those components still "in play" than most beds after a few years, so I don't see a reason to push their levels up at the start.

I didn't put vermiculite in the first year of SQGing. I put some in this year and am MUCH happier with the quality of the mix. It doesn't get impacted as compost can get and it definitely makes for better water retention. Go for it!

I did one of my 12 beds according to the formula found in Mels book. Like you i winced at the cost, but so far, i am truly impressed with the results compared to my other beds. I only have the cool weather crops in so far, but the broccoli and lettuce are performing exceptionally well. I make my own compost and am planning on expanding as that supply allows, and keep an eye out for a sale on peat and vermiculite.

I'm a bit disheartened by the responses, though I do appreciate them. Vermiculite simply is not available in my area. Not available at all. My husband persuaded me to sub the vermiculite with Miracle Gro garden soil for this first year, and I was hoping I'd have something at least close to the results I'd have with Mel's mix. Oh well, it was a nice fantasy. ;)

Is there anything at all to sub for the vermiculite? When it's not available, that pretty much limits one to subbing with *something.*

Just grow away with what you have. The primary thing the vermiculite would do for your bed is help with water retention.

Why not just use what you have and see how things go for you. If you find that your growing mix is requiring you to water more often than you like you can add a soaker hose on a timer and problem solved.

The thing about Sq Ft gardens is that over many years they become almost all compost anyway. The peat breaks down, the compost breaks down and the vermiculite breaks down (turns to mush). The only thing continually being replaced is the compost.

I think you will do fine this year and you can always tweak things for next year if you see a need.

From my experience with the various alternatives you are probably better off not subbing with most of them. Perlite has a nasty texture, a tendency to constantly "float to the top" and does not add the same water retention properties as vermiculite. Things seem to go down hill from there.

Certainly it is possible, at least in the US to order vermiculite over the internet, although not at a particularly good price. This is especially the case with the outfits that sell it as a packing material for shipping containers of liquids (apparently scientific liquid supplies are often shipped in bottles packed in vermiculite, which is absorbent and non-reactive). You should be able to buy it as a garden or insulating supply, although still at a sub-optimal price. Outside the US I have no idea availability wise. (I did find some almost good prices before shipping...)

Contact your local farmer's coop. I've been buying vermiculite online for years and thinking I was getting a good deal. I 30 mile drive out to the local farmer's coop yielded me 4sq. ft. bags of coarse grained verm for only $16 a bag. God I feel like i've been throwing money away on what I've ordered from ebay. Even if only on shipping alone...

It's at least worth a googling and a phone call to check... I can't imagine any reason they'd not have it - although a lot of local nurseries and big-box stores around here that I called told me they didn't stock it.

Outside the US, I think south africa is the only other place it's commonly mined (mica, that is)

Don't get discouraged...lots of folks grew nice gardens, including myself, before the idea of using vermiculite came along. However, here is a link from Sun Gro, a big agricultural company that markets it, and they have a retail place in Nashville. Maybe it will help you out.

http://www.sungro.com/retail_displayState.php?null=''&city=NASHVILLE&state=TN&country=

Thanks so much for the encouragement. I'm so enjoying watching my beans and peas pop up through the soil, and my tomatoes beginning to bloom and bear (verrrry tiny) fruit. I never even thought about the farmer's co-op...next time I'll give that a shot. Since budgetary concerns are extremely important, I'd rather not buy online unless the current mixture is just very unsatisfactory.

Some Building supply companies, some nurseries, often landscaping companies have agriculture grade vermiculite for less than 12 dollars a bag. I've paid as little as 8 dollars for a 4 cf bag.

~tom

Arjo, which coop do you get your vermiculite from? Ive looked around some this weekend HD, Lowes, and the Farmers Market nursery downtown and could only find 2 small 8qt bags.

Tennessee Farmer's Co-Op...

Specifically the Davidson County Farmer's Coop on Dickerson Pike just off I-65. $16 USD per 4cu. ft. bag. They had 17 bags in stock when I was there that day and after buying five of them I'm sure they replenished some of that by now.

By the way, it's Joe. ;-p

My username is my real name, psuedo-phonetically. R. Joe Reich = arjo_reich No one ever get's that. :shrug:

I have been doing a little research & have discovered that vermiculite is not the safest thing to use. Here is the Wikipedia link: http://en.wikipedia.org/wiki/Vermiculite

I just bought several bags of it to start my square foot garden, but am now trying to figure out what else I could possibly use. My children are the ones who help me in the garden & I would hate to think of them breathing in carcigens.Vermiculite its self is not harmful, but (at least in the bags I bought) another ingredient is added that is. Do all vermiculite bags contain more than just vermiculite? And if anyone has a bag that does, I'd love to know what brand it is.

I have been doing a little research & have discovered that vermiculite is not the safest thing to use. Here is the Wikipedia link: http://en.wikipedia.org/wiki/Vermiculite

I just bought several bags of it to start my square foot garden, but am now trying to figure out what else I could possibly use. My children are the ones who help me in the garden & I would hate to think of them breathing in carcigens.Vermiculite its self is not harmful, but (at least in the bags I bought) another ingredient is added that is. Do all vermiculite bags contain more than just vermiculite? And if anyone has a bag that does, I'd love to know what brand it is.