Several cameras will let you attach sound memos to a picture.
Canon will let you record up to one minute (for each Memo).
But I doubt that you will find it convenient for what you are doing.
To attach a sound memo takes many steps, using the menu.
You have to select the sound memo feature
Then select the photo that you want to attach it to.
Then make the recording.
Then go back to the picture taking mode.
Plus, to retrieve the information from the Sound Memo, you will have to know how to spell the name of the plant.
And with some of the plant names that I have seen, that can be a challenge.
It is much easier to just take two pictures.
One of the plant and one for the label.
Since they will be numbered in sequence it is easy to see the association.
I am pretty sure that all of the newer Canon SD series of cameras have "Sound Memo"
I attend a lot of field trials taking pictures of plants. I have to first take a shot of the label than the plant. Is there a camera that would allow me to either write on the screen or even talk into it before i take the picture? this would save me having to take two pictures ever time.