Actually, it's attached to your image above, ceating a discussion thread which appears in the Plant Photos forum.
Click on the entry,
Suppertunia Black Cherry, scroll down below the images and you can see that you have started two discussions attached to your images. You have to click them to read the post.
Now compare that to another entry where someone used the 'Post a Comment' under the "Adding Actions' box on the left side. It also appears below the images but the comments are visible as part of the entry, these comments are for personal growing experiences and additional details about the plant.
Petunia Celebrity Blue
By the way, it's not for comments about the differences in colors of the various images or if you agree or disagree about the given names of the plants, that is for discussions in the forums.
