The planters have been funded by a government grant distributed by Wiltshire Council under its towns programme, aimed at transforming high streets.
The troughs use downpipes to catch rain water which then supports the plants.
Emma Binns, from ARK, said: “That helps take water out of the combined sewer network – if that’s where the pipes go – and it also can filter the water that goes in there [the planters].
“This is just the first phase. We hope that it will spark some interest and people may just go ahead and make their own rain planters, and we hope to have subsequent phases of this project in the future.”