Please share with us what "plant" superdrol comes from or better yet what bottle of superdrol do you have that says "FDA approved" on it..
And no they dont regulate plants.. They regulate the products. There rules for dietary supplements are actually pretty lenient (compared to other industries) and companies try to slip one by all the time. It is pretty self regulating at the moment but I would imagine that wont last that much longer especially with all the "tainted", "spiked" and synthetic drugs they sell.
Superdrol is not DSHEA compliant (meaning it does not occur naturally) and thus a drug and requires FDA approval hence illegal from day one. It is also a anabolic steriod hence being listed as a schedule 3 drug now.
To back what I am saying, do me a favor and simply google "does the FDA regulate vitamins, and supplements" See what you get, first off the FDA is to busy regulating the ungoing food hazards we face everyday to have a predominant foot in this door. However, he FDA can withdraw vitamins (and other supplements and foods) only when danger has been proven. What you're likely thinking of is the way the FDA regulates drugs. The difference can be subtle: a claim to cure a specific disease or treat a certain condition makes something a drug instead of a supplement. For example, if your pill says it will "improve heart function," it's considered a supplement, but if it says "improve hypertension," it's considered a drug.
DRUGs are at minimum regulated by the FDA and often take years, 100's of millions of dollars in trials to prove safety and efficacy, and literally truckloads of paperwork. You or I could sell a SUPPLEMENT we made in our garage tomorrow and the FDA would have no legal power to regulate it.
Technically, the FDA doesn't approve or deny any supplements aside from general vitamins and minerals (those that have an RDA), they aren't "approved". If it was "FDA denied" (eg. contaminated product, bottles not containing the right product, etc), it's removed from the market and/or the company making it gets shuts down.
It's already happened a number of times... one of the biggest cases I can think of is when they banned Tryptophan for around a decade because of a contaminated batch that some people died from. It was banned that long because of misinformation that came up about it and partially from media coverage that spread that got some people thinking that it was the supplement, not the company.
With all that being said, there actually are watchgroups and organizations that do regulate supplements and regularly report to the FDA for any major adverse reactions (and the supplement companies that sell them are supposed to report these as well). The GMP (Good Manufacturing Practices) and USP (U.S. Pharmacopoeia) are the main quality assurance organizations (USP is for the U.S., GMP is for the U.S. and worldwide).