Ah! I think I'm able to see now that I've caused confusion by asking for the thumbsup. I often use it as a way of saying thank you to the poster for taking the time to share knowledge or information that really helps me out. I never even thought about it being applied to the original poster's opinion.
Sorry for the mix up. What I'd really like to be able to do is to say thank you without starting a thread for each one that says something like, "Thank you for sharing this! I didn't know where to find such-and-such plant, and now I do! ", and answered with, "You're welcome". I probably wouldn't have known about or used the company before and wouldn't have much more to talk about at that point, so the thread would likely end there. (Once I'd used the company and was happy with it I'd then write my own recommendation, so I'd likely forget to revisit the thread I'd started, anyway.)
Originally, I'd thought that the thumbsup would be a way to express my appreciation of the knowledge I'd gained, plus, it would offer the additional bonus of being a way to mark it to track it back when it was the proper time to order merchandise.
Thanks, greene, for helping to clear up my confusion.
Now that I'm seeing this from a different angle, the thread method does seem to be the best way to go.