The diversity of Mount Olympus ecosystems is the reason behind its rich flora. One of the most beautiful flowers hikers and climbers happen upon during their trails is the orchid. For those in the know, the mountain represents a field of special interest as there have been recorded over 50 orchid species. At an altitude of 300 to 500 m. (above Vrontou and Dion) the following varieties grow: Anacamptis pyramidalis, Anacamptis morio, Dactylorhiza romana, Neotinea tridentata, Orchis simia, Ophrys mammosa, Ο. oestrifera, Ο. oestrifera-minuscula, Ophrys helenae. At 500 -1.000 meters-high (by the northern slopes of the mountain and over the Valley of Kserolakkia) the Ophrys zeusii, Orchis purpurea, Cephalanthera rubra and C. Damasonium types of orchid make their appearance. Dactylorhiza saccifera is met in the eastern and northern slopes of the mountain. Epipactis atrorubens and Cephalanthera rubra are usually found at an altitude of 1.000 to 1.400m. The best period to visit in order to discover them is from April to July.