"Flowers are inserted into an acrylic tube containing a magnetic coil and an oscillating component. Applying an alternating electrical current causes the tube, and the flowers, to vibrate at high speed, producing audible sound."
Apparently it can reproduce audio from a CD or the radio. Naturally "some experts remain sceptical about the idea", questioning the sound quality from such a flexible component ... but who cares about sound quality if we can make flowers sing!
I think this page on the Let's site may be about the system.
Last word to Let's, with this fabulous and bizarre quote:
"We have added the fifth and final sense, sound, to the four senses already expressed by flowers - colour, scent, taste, and touch," the company said when launching the technology."