I've used both albeit for different reasons. Vermiculite was used in my aquarium setups as it can retain and slowly release iron (at least that is what I've read). Perlite I use pots for houseplants. I doubt that it is just styrofoam but am willing to be corrected on this. 2 years ago I broke up some new ground for my vegetable garden and the soil was pretty much clay. In the late fall I added in 2-3 cubic feet of peat moss. Come the Spring where I added the moss was sooo easy to work. So, I'd add homemade compost first and if none were around use the moss. YMMV

Vermiculite IS a clay, so it just makes it worst. The best thing, actually, for clay soil is leaf compost, but in the absence of that, I'd add manure and coarse sand.

Perlite isn't styrofoam. It's a volcanic rock. Some growers use styrofoam pellets in lieu of perlite in their mixes, because it doesn't float to the top like perlite.

Organic matter, definitely. Leaf compost is perfect if you've got it, or just dried leaves or lawn clippings tilled in lightly and left over the winter. I respectfully disagree with bruggirl about the sand, though. It sounds logical that if sand drains too fast and clay drains too slow, a mixture should do well, but in my personal experience, clay + sand = concrete. Perlite is fine for pots, but I don't think it would do much good in clay soil, not to mention that it's awfully expensive!

My soil is a natural mix of sand and clay and yes, Anarie, it turns to concrete. I added wood chips as mulch and the next season tilled it in for a wonderful improvement. Now, as I add in more wood chips it continues to improve. The wood chips (and leaves) disappear in the soil over a season.

Perlite here is really cheap right now due to year end clearances. I'm going to get *some* I want to do a raised bed with a *soil-less* mixture as an experiment. But need something for the other beds.

I added both wood chips and gypsum. Gypsum's OK but the wood chips!! I really noted an improvement with them.

Re sand, I once read where you'd have to add so much you'd go broke buying sand to make a difference.

You have to be careful on the wood chips (can't have any treated wood in there) but if you can get them, they're the best.

Cher

We all garden on a clay base here...The link has a great recipe for improving clay that works anywere though. Please note the sequence of adding compost/organic matter and sand...organic materials first, then sand to eliminate the possibility of making cement. (80#s coarse sharp sand from a builders supply is about $3)

Here is a link that might be useful: improving clay

Vermiculite and Perlite are not clay!
Vermiculite is a mineral called mica that's been heated and expanded.
Perlite (the white stuff) is volcanic rock heated and expanded (like how you pop popcorn you go from a hard kernal to a soft piece or pop corn, same deal applies here. Hard minerals exposed to extremely high temps will make them pop) The person whoc said about perlite not decomposing is absolutely correct. Rock will not decompose, and therefore that is why only one treatment of perlite is suffice to last years and years

Blessed, I went to my local 'Rock Products' center, where they sell different sized gravels, sands, mulches etc. They have a product called 'soil pep', which is supposed to be a by product of the lumber mill industry. Little tiny chunks of wood, and it does great to loosen up clay soil. I didn't think it was too pricey (but you do have to pay some $ for it), I just filled up the tall sized rubbermaid in the trunk of my car, I used it as a mulch in my containers, but had some extra to work in around my plantings in the garden, and I love how loose the soil feels when I poke my fingers in to check for moisture. I paid about $4 for the rubbermaid quantity.

Perlite comes from a type of rock that when heated expands 20 times its normal volume. This article will tell you more than you want to know about it. Here in southern California you can buy it for around $8 for a 4 cubic foot bag. Be careful not to breathe the dust from perlite or even peat moss.
http://www.perlite.net/

Why do we need to be careful breathing possible dust around peat moss or perlite?

~Angela

According to another discussion, you can get silicosis.

http://forums2.gardenweb.com/forums/load/strucs/msg0116233421772.html

Breathing in small dustlike particles of anything is generally not good for you.

Don't know if this is a coincidence, but my cold/cough seemed to have subsided this morning, but acted up in the afternoon right after I'd been mixing perlite/peat moss/compost for a new container.

I am surprised no one mention's using expanded shale. I have not used it but have heard of others using it with good results. Might check it out?

I use dried out grass clippings and leafs topped of with mulch.

Here is a link that might be useful: expanded shale - a new possibility for amending clay soil

Since this is the 'frugal' gardening forum have you thought of not buying either perlite or vermiculite? I have gardened all my life and have never had occasion to use either. My vegetable gardening is done on heavy clay sil to which I add manure and home made compost.

When you say you add "wood chips," what does that mean, exactly? Do you just get mulch? Or is it something different?

I need help with my soil...it's about as bad is it can get. Solid clay, except for the gravel that's mixed in. 2 inches down I can pull out rocks that weigh 50+ lbs.

Does Gypsum really work? A lady at the local nursery told me it does, but I read online that there is a debate on whether it does or not...

First off vermiculite is used only in potting soils for drainage. Perlite is used in potting mixes also to give roots plenty of oxygen. You would never use perlite in the ground. That's not the purpose.

Quite a few inaccurate comments in here. Since the thread is old I will just address the last comment.

Perlite is used for many different applications with native soils. Specifically golf courses and football fields.

http://www.perlite.org/perlite_info/guides/plants/HORTICULTURAL%20PERLITE%20-%20THE%20NATURAL%20GROWING%20MEDIA%20FOR%20OUTDOOR%20GARDENING.pdf

Perlite will help with clay soils in regards to compaction and drainage.

Besides being a manufacturer of Perlite and Vermiculite I was a landscaper for 15 years and amended many perennial beds with heavy clay soils with success. Never hurts to add compost also to bring the nutrients where they need to be also. Perlite and Vermiculite are neutral PH and sterile hence they don't help with soil nutrients.

Have a great day,
Mike

Here is a link that might be useful: Perlite plant guide