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plant collections fall 2016 33 A Potpourri of pan dans TEXT AND PHOTOS BY CHAD HUSBY The Genus Pandanus Pandanus plants (family Pandanaceae) are distinctive woody monocots of the tropics and subtropics, ranging from West Africa through Asia and the Pacific all the way to Hawaii and Pitcairn Island. They grow as trees or shrubs in diverse habitats from the seashore to swamps, riversides, and forests. There are about 450 species known and new species continue to be discovered. The largest species can reach 60 feet or more in height, with leaves 15 or more feet long. As monocots (like palms and bamboos), they lack the secondary woody growth produced by most trees, so their stems do not continually increase in diameter as they grow. The tight spiral arrangements of their leaves leads them to be called “screw pines” or “screw palms,” though they are often simply called “pandans.” This spiral pattern remains imprinted on the stems in the form of leaf scars after the leaves are shed. Many Pandanus exhibit branching, which is constrained by the inability of their stems to increase in diameter with secondary woody growth. Some species have a marked difference in orientation between an upright central trunk and horizontal branches, creating architecture not found in any other woody monocots and leading to surprising similarities with woody trees. This differentiation can be so great, with horizontal branches that cease growing once they reach a certain length, that some species in Madagascar develop a very regular architecture resembling conifers. Other species are either solitary or form clumps of unbranched trunks, their architecture much like that of typical palms. A distinctive feature of this genus is the large aerial (stilt) roots that emerge from the trunks of most species. These roots can form a dense skirt around the trunks, providing benefits in trunk support and water transport


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