I have super thick solid tree trunk thighs... but I want slender thin flower stems! (Photo)

 Changing the overall character of your thighs  is going to be tough. Weight loss would help, and there may be a role for some liposuction/liposculpture. "Thin flower stems" would require extensive skin and fat removal and you should think about that long and hard  after you have consulted with a board-certified plastic surgeon with extensive experience doing major post-weight loss procedures. Best of luck to you. 

Thank you for the photos. Though they do not tell the whole story, they do suggest that you could benefit from liposculpture. The key is the artistry of your surgeon, and your expectations.  See a board-certified plastic surgeon who does a ton of Lipo-sculpture and operates at a certified facility, and you will be in good hands. Do not shy away from asking; how many thighs, like mine, have you sculpted? Do not settle for a vague answer, then ask to speak to a patient who had a similar procedure. Do your homework, see more than one plastic surgeon, and good luck. 

Your thighs would have to be evaluated in person to determine if you have enough subcutaneous fat for liposuction to be effective.

I do not have the advantage of examining you but the photos seems to indicate quite muscular anatomy that are reasonably well-defined and not obscured by thick layers of fat except perhaps on the lateral upper thigh area and medial knees. One very important aspect to cosmetic surgery that point out to patients is that choosing to do surgery is really trying to distinguish self from non-self. There are anatomical features that patients feel are "not who they are" and those want to change them with the expectation that what results is more who they are. But just as important in this equation is being able to accept who you are and anatomy that you can identify with or accept as "self". The more you accept "self" and the less you wish to change "non-self", the better candidate you are for cosmetic surgery. You might get some benefit from judicial liposuction but going from "tree trunk" to "flower stem" is probably wishful thinking.