|Field Trip - Indiana Dunes National Lakeshore - 4 of 12
By Paul Katula, Dateline: GARY, Ind. (May 27, 2006)
Cottonwood trees also help secure the sand:
The cottonwood tree has distinctive "spade-shaped" leaves. The key to this tiny-looking tree, though, is not the two feet of it you see above the surface, but rather the 60 feet or so just below the sand. The stems of the cottonwood tree, like the rhizomes of the marram grass, help to build up the dune by holding sand in place. They function as roots when the sand buries them. Unlike marram grass, though, the cottonwood needs a sheltered spot in order to sprout.