My father, Errol Groves, who has died aged 69 of cancer, was an activist, gardener, musician and co-founder of the Vale Earth fair, an annual charity music festival held in Guernsey, the Channel Island he made his home.

Every August bank holiday at the fair, around 2,000 people and more than 60 acts gather across five stages at the 15th-century Vale Castle, which Errol chose as the island’s best venue for live outdoor music. The two-day festival is volunteer-run and – largely thanks to Errol’s influence – as green as possible, with all-vegetarian food stands, profits donated to humanitarian causes and everything possible recycled.

Born in Banbridge, Northern Ireland, one of five children of Eva (nee Davis), a shopkeeper, and David Groves, a farmer, Errol attended Banbridge academy. After leaving school he travelled in 1966 to Guernsey, where he had heard there were jobs to be had. An anarchist who was passionately anti-establishment, he helped bring 1960s and 70s counterculture to the island.

He set up his own gardening business, called Earthworks, in the 70s and made it his life’s work, with a roster of loyal customers. A gardener by day, he was a musician by night, playing the bongos and conga drums with panache in three local bands over the years: Two Trumpets, the Coal Hole Combo and Edith’s Head.

His contribution to the island’s music was also to arrange gigs in unusual venues, inspiring others to do the same. In the summer of 1976 he took things further with some friends, and planned Guernsey’s first one-day festival. He was involved in the Vale Earth fair for 41 years and was the only founder who retained a big role in what is today the Channel Islands’ longest-running music festival; what he once called “the best little festival on the planet”.

Resolutely leftwing, in 1982 he co-founded Radical Island Press, or RIP, Guernsey’s alternative magazine, which ran for several years. Other initiatives included the Peace Field, a crop-growing, horse-ploughed field to raise money for good causes in 1985, a three-day outdoor fast against the Gulf war in 1990 and protests against local plans for an incinerator in 2004.

The last part of his life he spent mostly at Duvaux farm, a granite farmstead where he tended his allotment and kept his chickens, spending his time discovering new music online, reading, and, as a Manchester United fan, listening to the football on the radio.

Ever supportive of the underdog, he will be remembered for his kindness, the passion of his beliefs and the joy of his company.

He is survived by three children, Siubhan, Michèle and me, from his 1972 marriage to Carolyn Myryam, which ended in divorce in 1989; a son, Yves, from his relationship with Hayley Le Marquand; three grandchildren, Eloise, Milla and Rudy; and his four siblings, Anne, Gordon, Brian and Enid.