A new and distinct variety of Lomandra longifolia plant, designated 'LM300', is characterized by a fine, narrow leaf blade, and compact habit as compared with other varieties of Lomandra longifolia. 'LM300' is further characterized by a yellow green to deep-green leaf blade color with greyed orange to greyed purple basal shoots. In addition, 'LM300' is cold tolerant with excellent color retention as compared with other varieties of Lomandra longifolia.