Hermitage, where the heel of Roxburghshire kicks into the once-lawless Debatable Lands, seems an unlikely place to find a botanical artist. It’s hard to make anything grow here, let alone an exhibition-load of rare and sometimes exotic plants. Lorded over by Hermitage Castle, a menacing hulk of medieval brutalism described by George MacDonald Fraser as ‘shouting “sod off” in stone’, this is a remote, rarely visited stretch of the border.