Maggie McElroy, 50, of Towyn said she went out to the store and returned to discover friend Barry Brennand, 65, had filled her "pride and joy" flower beds with 6 feet of suds, The Sun reported Thursday.
McElroy said Brennand's prank was revenge for the time she filled his garden with a zoo's worth of stuffed animals while he was away on vacation.
McElroy laughed off the prank with a foam party in her yard with Brennand and other neighbors who were in on the joke.
"I thought I'd left my washing machine on until I heard giggling. But I'll get him back," McElroy said.