Complex sentence: Following the end of the war the arboretum was neglected by a series of different owners until 1958 when the Silesian Museum took control of the site, and restored the original style, consisting of both solitary and mixed groups of trees spread around open areas.
Split into simpler sentences: Following the end of the war the arboretum was neglected by a series of different owners until 1958 when the Silesian Museum took charge. They restored the original style which consists of both solitary and mixed groups of trees spread around open areas.