Thanks to the terrain, which is very complex geomorphologically, the park is exceptionally rich from a natural science point of view. Here you can find rocks, and shady and sunlit woods. In the Blanice River floodplain there are damp meadows, and the area below the Old Castle has a primeval character. Many rare and protected plant species grow here, such as European Monkshood and Martagon Lily. English Oaks grow in the woods, and other giants of the forest grow all over the site, which is home to rare insects and birds, for which the park is the last refuge in a wide area. Vlašim Park has therefore been included in a European register of nature reserves.