Complex sentence: The Grade I listed house is surrounded by one of Europe's largest rock gardens, a large number of rhododendrons, and a large collection of mostly coniferous trees, among which one Douglas-fir is the tallest tree in England, at 59 m tall.
Split into simpler sentences: The Grade I listed house is surrounded by one of Europe's largest rock gardens, a large number of rhododendrons and a large collection of mostly coniferous trees. One Douglas-fir is the tallest tree in England, at 59 m tall.