Iva annua
（重定向自Marsh elder）
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Iva annua, sumpweed or marshelder, is a North American herbaceous annual plant in the sunflower family. It is native to northeastern Mexico (Tamaulipas) and to the central and southern United States, primarily the Great Plains and Mississippi Valley as far north as North Dakota. There are some populations in the eastern US, but these appear to represent introductions.