The Park derives its name from the giant guanacaste or tubroos tree growing near the southwestern edge. This colossal old tree shelters a large population of epiphytes, or airplants, among its branches and to view it is well worth the short walk from the park entrance. The guanacaste or tubroos tree is a fast-growing species and one of the largest trees found in Central America. The tree has a large, flat, wide spreading crown, pale green leaves and small white flowers. The seed pods are broad, flat, shiny dark brown, three to four inches across, and coiled into almost a complete circle, somewhat resembling a human ear.
Cattle feed on the leaves, flowers and pods.
Tubroos is a favourite timber for the dugout canoes that Belizeans call doreys. The wood is not readily attacked by pinworms. Feeding troughs and mortars for hulling rice are also made from the tubroos tree. The guanacaste tree escaped being made into a dorey despite the tree's easy access to river traffic. The trunk, instead of growing straight, divided very near the base, so that the tree, instead of having one straight trunk, has three.