I noticed today that we have a garden tag. It is currently applied to 17 questions, and is the only tag on 5 of them.
Now, the gardening tag is blacklisted because it's an intrinsic tag, one that is so general that it could be applied to most or all questions on a site. There is also the concept of a meta-tag, which is one that doesn't describe the contents of the question on its own and relies on other tags to give it context.
I would argue that garden is intrinsic because it's closely related to the word "gardening", and a large proportion of our questions could have it applied. I'd also say that it's a meta-tag, since it doesn't help to describe the questions it's used on: looking through that list of questions, it could be removed from all of them without altering the meaning of the question.
Should we ask to have this tag blacklisted (Stack Exchange staff will do the actual blacklisting once it has been discussed)? If we do, we'll need to re-tag those questions to remove all uses of the tag, then submit the request.