'Rhubarb is a radio idiom for unintelligible background speech. Typically extras would mutter the word over and over to provide ambience for a crowd or party scene. In The Goon Show the cast was usually only the three principals, who would pretend to try to sound like a larger group by repeating "rhubarb" very quickly but clearly, with outbreaks of "Custard!" for good measure.'
With thanks to Wikipedia
The first harvest of the year from my garden. I've had a stalwart rhubarb plant sitting under a bucket which has been weighted down with a large granite sett to stop the wind blowing it away, and look how rewarded I have been! The ruby red has now been cooked gently and sits happily mixed into a tub of yoghurt. No custard.