Calcium oxalate crystal formation and leaf toughness were measured and compared in five species, (Cyclanthus subpalmata, Pandanus leram, Crinum amabile, Heliconia longiflora and Guzmania zahnii) pre-selected for known leaf raphide production and toughness. Nine to eleven representative individuals from each species were randomly selected for the same microenvironment. The study was conducted in Las Cruces, Costa Rica. Leaves from each species were classified as two age classes: young and mature. Leaf crystal number was quantified by light microscopy. Leaf toughness was measured with a penetrometer. For all five species, the number of crystals was highest in young leaves and lowest in mature leaves. In addition, crystal formation was inversely related both to the leaf age class and to leaf toughness. It is proposed that crystal formation may be an alternative plant defense to toughness in young leaves.