I think it's a song called Mountain Dew and has been done by Robert Plant and The Grateful Dead - not sure which orginally. It's on an album by Robert Plant called Dreamland.
Morning Dew was actually written by Bonnie Dobson alone, it was not co-written with Tim Rose. It was released on a Bonnie Dobson LP "Live at Folk City" recorded at Gerdes Folk City, New York in 1962, way before Tim Rose came on the scene. Tim Rose changed some words for his version and US copyright laws enabled him to claim co-song writing credit but Bonnie, some time ago, completely established her rights to being credited as sole author.