A probe is underway to ascertain how cannabis plants came to bloom in official council flower pots.
Around 20 plants could be seen sprouting from at least six separate locations in Newport city centre in the past week.
Shopkeepers Dean Beddis and Steve Reynolds told Wales Online: “I have never seen cannabis growing in the wild before so it was crazy to see it.
“We thought Newport was trying to be a new Amsterdam and doing its best to win City in Bloom.
“It’s actually a rather beautiful plant and stood out wonderfully. But they have gone now. I don’t know who took them.”
A Newport Council spokesman told the Huffington Post UK: "The council made an inspection of all its planters on 1 August and did not find any evidence of cannabis plants. The planters also did not look as though they had been disturbed.
"The photographs provided by the report appear to show mature plants added to a council planter.
“Although this could be a hoax, it is a serious issue and Newport City Council will be informing the police, and checking its CCTV cameras for additional evidence. If anyone has any information about this the council hopes they would contact the police."