Walls don't have ears, but apparently plants do..

Crowley had heard about talking to plants in the seventies, and thought it a great idea. Not only did he terrorise his plants into growing, though, he also passed the time in his rather lonely flat by chatting to his plants. He found it rather therapeutic to be able to talk endlessly about his fears, hopes and dreams, and for it to feel like somebody was there to listen.
One day, after the averted apocalypse, Aziraphale wandered into the flat looking for Crowley. He had needed help with cleaning out the back of the bookshop (he thought it about time, it hadn't been cleaned in at least a century).
Instead of finding Crowley, though, Aziraphale found himself standing in the middle of the flat, surrounded by plants covered in shimmering gold words...