Later - in the early '60's he became interested in folk and bluegrass. His mother listened to the Grand Ole Opry shows on the radio when he was a kid, and he grew up listening to Bill Monroe, Flatt + Scruggs etc.
He was in two bluegrass bands in the early '60's. One was called the "Hart Valley Drifters". After that he got more interested in jugband style music. He played Scruggs style (for want of a better term) banjo, and then a more claw-hammer style banjo with the jugband format. The jugband he was in was the proto-Warlock group, that was the proto-Grateful Dead group.
Garcia also played banjo in the 70's in a group called the Great American Music Band. David Grisman - mandolin; Richard Greene - fiddle; David Nichtern - guitar; Taj Mahal - bass (sometimes).
In addition to the people mentioned, Old & In The Way included David Grisman on mandolin and Peter Rowan on guitar and vocals.