Early progenitors of what later came to be termed "acid folk," London's Trees launched a relatively brief creative campaign between their 1969 formation and 1973 dissolution. In between, the quintet managed two studio albums for CBS while gigging heavily in support slots for bigger names like Pink Floyd, Fleetwood Mac, and Genesis. Arriving at the crest of the U.K. folk-rock boom, Trees had a similar makeup as Fairport Convention's storied Liege & Lief lineup with their own enigmatic frontwoman in Celia Humphris and a daring lead guitarist in Barry Clarke. Also like Fairport, they put a rugged electric spin on traditional British material which they supplemented with originals in a similar vein written by bassist Bias Boshell. However, it was Trees' progressive bent and, in particular, their penchant for unruly psychedelic jamming that set them apart from the cream of the folk-rock crop. Often thrilling and occasionally shambling, the group's post-career legacy grew toward the periphery as their records -- 1970's The Garden of Jane Delawney and 1971's On the Shore -- slowly accumulated cult classic status, thanks to discerning collectors who heard something unique in their approach. Released by Earth Records a half-century after their debut, this eponymous four-disc anthology celebrates Trees' story, gathering both albums along with a bevy of remixes, demos, BBC sessions, and other assorted rarities. Listening to the whole of their catalog, time has been kind to the group, for the most part. Less whimsical than the Incredible String Band and lacking the polish of Steeleye Span, Trees' folk-rock exists in a more liminal place where early-'70s rock guitar bounty meets the pastoral woodsiness of folk. On "The Great Silkie," Humphris' dulcet voice and David Costa's crystalline acoustic work soon give way to a muscular second half, transporting the song from misty folk ballad to druggy, off-the-rails psych rock. This push and pull between melodic structure and cerebral sonic wayfaring plays out even on the quieter acoustic cuts, but it's the full-band romps where Trees take the most risks. Bookended by some neatly arranged orchestral and vocal work, the excellent "While the Iron Is Hot" is pure rock lightning in its heavy middle section. These fractious shifts are likely one of the reasons Trees couldn't capture a larger audience during their existence, but in hindsight, their unpredictability is a big part of their appeal and this warts-and-all set reveals an exciting if occasionally flawed band.