What you'll find here is "prensado paraguayo" (like the mexican bricks) -> strong ammonia smell, really harsh to smoke but does the job (rather a stoned effect than a high one).
That's just what you find easily, that you can pretty much find just by walking down the street and smelling in certain places. I hear they actually soak it with Coca-Cola to get it to press into the bricks. If it smells ammonia-ish is may have gone moldy...
Flowers are available, but like most things, you have to know someone. And that can be tough with this subject - many Argentinos with the good buds won't sell it and you have to find them when there is extra. However, there are some producers...