Zizania palustris L.

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Wildrice grows in shallow water and on muddy shores, mainly in the north central United States and adjacent Canada. In Iowa, wildrice is found scattered primarily throughout the northern half of the state with records from a few counties in the southern half (Ringgold, Johnson, Muscatine, and Louisa), but it is relatively uncommon. The plants are usually found growing with their bases in mud or more commonly in water no more than 2 feet deep (Runkel & Roosa 1999) with the rest of the leafy stems and flowering heads easily visible. The plants are often large, reaching up to as much as 10 ft. in height (Runkel & Roosa 1999). This species is distinctive because of the large flowering heads with the male (staminate) spikelets borne on the spreading lower branches and the female (pistillate or grain-bearing) spikelets borne on the more or less erect (but sometimes spreading) upper branches. After flowering in July and August, the male spikelets quickly fall off, leaving the lower branches naked. When ripe, the grain-bearing female spikelets fall off (shatter) easily in wild plants, but they remain on the flowering heads in cultivated strains. Although best known as a grain harvested by Native Americans, and subsequently brought into cultivation in a number of areas, notably California, wildrice is also an important food source for wildlife. Runkel & Roosa (1999) note that in Iowa, the grains are often parasitized by a weevil, which markedly reduces seed production.

Two varieties of wildrice are recognized in Iowa. Interior wildrice (Z. palustris var. interior) is by far the most common; northern wildrice (Z. palustris var. palustris) is only known from four counties in central and northwestern Iowa (Story, Lyon, Palo Alto, and Cerro Gordo). Interior wildrice has wider leaves and the lower female branches tend to have more spikelets per branch than in northern wildrice. Sometimes the two varieties intergrade and it can be difficult to distinguish them. The female part of the flowering head is supposed to be much narrower (1-8 cm wide or occasionally up to 15 cm wide) in northern wildrice, and usually 10-20 cm wide in interior wildrice, but all of our material is like northern wildrice even though the two varieties can be distinguished using the differences mentioned above.

Etymology: Zizania from the Greek zizanion = growing in water; palustris (Latin) = swampy and marshy, referring to the typical habitat of the species; interior (Latin) = inner, interior, referring to the distribution of this variety in the interior of the continent.


Plants annual. Culms to 1-2 (3) m tall, erect, the bases usually in water. Leaves with the sheaths smooth; ligules 10-20 (-24) mm long, the margin often more or less irregular; blades 25-73 (-82) cm long, (6-) 9-35 mm wide, smooth. Flowering heads (29-) 36-57 (-64) cm long, 5-26 cm wide; male branches below, ascending or spreading; female branches above, mostly appressed or ascending, sometimes 1 to a few spreading. Male lemmas 5.5-11 mm long excluding the awn or awn tip, usually purple, sometimes greenish, the tip or the awn 0.3-1.5 (-5.5) mm long. Female lemmas 9.5-17 (-19) mm long excluding the awn, 1.2-1.6 mm wide, leathery or hardened, shiny, smooth or with lines of hairs, the tip usually with coarse, stiff hairs, the awn 17-55 mm long; lemma and palea remaining closed at maturity. Chromosome number 2n = 30.


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