Photo by Peter McIntosh.
Garden information services officer Clare Fraser said staff noticed the "completely random" lime-green leaves on Tuesday.
Though she had "no idea" who had put them there, they "looked like they planned it".
The plant was due to be removed from its spot in the rock garden, but "we can't rip something like that out in a hurry", she said.
Dunedin City Council botanic garden and cemeteries team leader Alan Matchett described it as "a wonderful piece of art", and while he did not generally condone the practice of attaching foreign objects to plants, this case was an exception.
The pair were interested to know if any more crochet was planned, and would like to meet the creator.
