5.04 ZIZANIA L.
Edward E. Terrell
Plants annual or perennial; aquatic, usually rooted in the substrate; sometimes rhizomatous or stoloniferous; monoecious. Culms to 5 m, erect and emergent or floating. Leaves concentrated on the lower portion of the stem or evenly distributed; sheaths open, not inflated; ligules membranous or scarious, glabrous; pseudopetioles absent; blades flat, aerial or floating, scabrous or smooth. Inflorescences terminal panicles; branches usually unisexual, lower branches staminate, upper branches pistillate, middle branches sometimes with staminate and pistillate spikelets intermixed; pedicel apices cupulate; disarticulation beneath the spikelets, in cultivated strains disarticulation delayed, the spikelets tending not to shatter until harvested. Spikelets unisexual, with 1 floret. Glumes absent; calluses inconspicuous; lemmas 5-veined; paleas 3-veined; lodicules 2, membranous. Staminate spikelets pendant, terete or appearing so; lemmas membranous; paleas membranous, loosely enclosing the stamens; anthers 6. Pistillate spikelets terete; lemmas chartaceous or coriaceous, margins involute and clasping the margins of the paleas, apices acute to acuminate, sometimes awned, awns terminal, slender, scabridulous; styles 2, bases not fused, stigmas laterally exserted, plumose. Caryopses cylindrical; embryos linear, often as long as the caryopses; hila linear. x = 15. Name from the Greek zizanion, a weed growing in grain.
Zizania includes three North American and one eastern Asian species. Zizania aquatica and Z. palustris are important constituents of aquatic plant communities in North America, providing food and shelter for numerous animal species. Zizania palustris is also an important food source for humans. Zizania texana is federally listed as an endangered species in the United States. Zizania latifolia, an Asian species, is available through horticultural outlets despite its potential for harboring a fungus that would devastate the native species (for additional information, see the comment following the species description).
SELECTED REFERENCES Aiken, S.G., P.F. Lee, D. Punter, and J.M. Stewart. 1988. Wild Rice in Canada. Agriculture Canada Publication 1830. NC Press, Toronto, Ontario, Canada. 130 pp.; Dore, W.G. 1969. Wild Rice. Canada Department of Agriculture Publication No. 1393. Information Canada, Ottawa, Ontario, Canada. 84 pp.; Duvall, M.R. and D.D. Biesboer. 1988. Nonreciprocal hybridization failure in crosses between annual wild-rice species (Zizania palustris × Z. aquatica: Poaceae). Syst. Bot. 13:229–234; Environment Walkato. 2002–2007. Regional Pest Management Strategy. Walkato Regional Council, Hamilton East, New Zealand. http://www.ew.govt.nz/policyandplans/rpmsintro/ rpms2002/operative5.2.7.htm/; Liu, L. and S.M. Phillips. 2006. Zizania. Pp. 187–188 in Z.-Y. Wu, P.H. Raven, and D.-Y. Hong (eds.). Flora of China, vol. 22 (Poaceae). Science Press, Beijing, Peoples Republic of China and Missouri Botanical Garden Press, St. Louis, Missouri, U.S.A. 653 pp. http://flora.huh.harvard.edu/china/mss/volume22/index.htm/; Terrell, E.E. and L.R. Batra. 1982. Zizania latifolia and Ustilago esculenta, a grass-fungus association. Econ. Bot. 36:274–285; Terrell, E.E., W.H.P. Emery, and H.E. Beaty. 1978. Observations on Zizania texana (Texas wildrice), an endangered species. Bull. Torrey Bot. Club 105:50–57; Terrell, E.E., P.M. Peterson, J.L. Reveal, and M.R. Duvall. 1997. Taxonomy of North American species of Zizania (Poaceae). Sida 17:533–549; Warwick, S.I. and S.G. Aiken. 1986. Electrophoretic evidence for the recognition of two species in annual wild rice (Zizania, Poaceae). Syst. Bot. 11:464–473.
For an interactive dichotomous key, click here; the interactive, multientry key is not yet available.
1. Culms decumbent, completely immersed or the upper parts of the culm emergent; known only from the San Marcos River in Hays County, Texas ... Z. texana
1. Zizania aquatica L.
Plants annual. Culms 0.2–5 m, usually emergent. Sheaths glab-rous or scabridulous; ligules 5–30 mm, upper ligules truncate to ovate or acuminate, often erose or irregularly lobed; blades to 1.5 m or longer, (3)10–55(75) mm wide, abaxial and adaxial surfaces scabrous or glabrate. Panicles 20–120 cm long, (5)10–50 cm wide; branches unisexual. Staminate branches ascending to reflexed; pedicel apices 0.2–0.6 mm wide. Staminate spikelets 5–12.5 mm, lanceolate, acuminate or awned, awns to 3 mm. Pistillate branches divaricate, sometimes appressed if immature or bearing only aborted spikelets; pedicel apices 0.5–1.2 mm wide. Pistillate spikelets 5–24 mm long, 1–2.5 mm wide, lanceolate or oblong, chartaceous and flexible, dull or sublustrous, with scattered short hairs, these not or scarcely denser at the apices, awned, awns to 10 cm; lemmas and paleas often partly separating at maturity; aborted pistillate spikelets 0.4–1 mm wide, linear, shriveled, often threadlike. Caryopses 6–22 mm long, 0.8–2 mm wide. 2n = 30.
Zizania aquatica is native from the central plains to the eastern seaboard. It is sometimes planted for wildfowl food. The records from western North America reflect such plantings. Most, possibly all, have since died out. The population in northern Arizona was discovered in 1967, and persisted until the early 1990s. It is presumed to have been extirpated because the area has since been developed into a golf course, and no plants have been found downstream.
1. Plants to 5 m tall; blades (5)10–75 mm wide; pistillate spikelets 7–24 mm long; awns to 10 cm long ... var. aquatica
1. Plants 0.2–1 m tall; blades 3–12(20) mm wide; pistillate spikelets 5–11 mm long; awns 1–8 mm long ... var. brevis
Zizania aquatica L. var. aquatica
Southern Wildrice, Zizanie Aquatique
Plants to 5 m. Blades (5)10–75 mm wide. Pistillate spikelets 7–24 mm; awns to 10 cm.
Zizania aquatica var. aquatica grows in fresh or somewhat brackish marshes, swamps, streams, and lakes. Its native range extends from southeastern Minnesota to southern Maine, and south to central Florida and southern Louisiana. Plants in the Wading River, New Jersey, grow mostly immersed; narrow-leaved populations occur locally in the New England states and near Ottawa, Ontario.
Zizania aquatica L. var. brevis Fassett
Plants 0.2–1 m. Blades 3–12(20) mm wide. Pistillate spikelets 5–11 mm; awns 1–8 mm.
Zizania aquatica var. brevis is known from tidal mud flats along the St. Lawrence River, about 80 km up- and downstream from Quebec City, and from a small delta along the northern shore of the northwest Miramichi River estuary in New Brunswick.
2. Zizania palustris L.
Plants annual. Culms to 3 m, erect, usually at least partly immersed. Sheaths glabrous or with scattered hairs; ligules 3–16 mm, upper ligules trun-cate, lanceolate or triangular, erose; blades 20–60 cm long, 3–21(40+) mm wide, glabrous, margins glabrate or scabrous. Panicles 24–60 cm long, 1–20(40) cm wide; branches unisexual. Staminate branches ascending or divergent; pedicel apices 0.2–0.4 mm wide. Staminate spikelets 6–17 mm, lanceolate, acuminate or awned, awns to 2 mm. Pistillate branches mostly appressed or ascending, a few sometimes divergent; pedicel apices 0.7–1.2 mm wide. Pistillate spikelets 8–33 mm long, 1–2.6 mm wide, lanceolate or oblong, coriaceous or indurate, lustrous, glabrous or with lines of short hairs, apices usually hirsute and abruptly narrowed, awned, awns to 10 cm; lemmas and paleas remaining clasped at maturity; aborted pistillate spikelets 0.6–2.6 mm wide. Caryopses 6–30 mm long, 0.6–2 mm wide. 2n = 30.
Zizania palustris grows mostly to the north of Z. aquatica, but the two species overlap in the Great Lakes region, eastern Canada, and New England. It is cultivated as a crop in some provinces and states, with California being the largest producer. All records from the western part of the Flora region reflect deliberate plantings; none are known to have persisted. In cultivated strains, the pistillate spikelets remain on the plant at maturity.
1. Lower pistillate branches with 9–30 spikelets; pistillate part of the inflorescence 10–40 cm or more wide, the branches ascending to widely divergent; plants 1–3 m tall; blades 10–40+ mm wide ... var. interior
1. Lower pistillate branches with 2–8 spikelets; pistillate part of the inflorescence 1–8(15) cm wide, the branches appressed or ascending, or a few branches somewhat divergent; plants to 2 m tall; blades 3–21 mm wide ... var. palustris
Zizania palustris L. var. interior (Fassett) Dore
Plants 1–3 m. Blades 10–40+ mm wide. Pistillate part of inflorescences 10–40+ cm wide; branches ascending to widely divergent; lower pistillate branches with 9–30 spikelets.
Zizania palustris var. interior grows on muddy shores and in shallow water, mainly in the north central United States and adjacent Canada. It resembles Z. aquatica in its vegetative characters, and Z. palustris var. palustris in its pistillate spikelets. Crossing experiments (Duvall and Biesboer 1988) suggest that hybridization between the two may occur. Isozyme data (Warwick and Aiken 1986) do not support the hypothesis that Z. palustris var. interior is a hybrid.
Zizania palustris L. var. palustris
Northern Wildrice, Zizanie des Marais, Folle Avoine, Riz Sauvage
Plants to 2 m. Blades 3–21 mm wide. Pistillate part of inflorescences 1–8(15) cm wide; branches appressed or ascending, or with 1 to few branches somewhat divergent; lower pistillate branches with 2–8 spikelets.
Zizania palustris var. palustris grows in the shallow water of lakes and streams, often forming extensive stands in northern lakes. It has been introduced to British Columbia, Nova Scotia, Idaho, Arizona, and West Virginia for waterfowl food; some of the stands in the Canadian prairies may also have resulted from planting (Aiken et al. 1988).
3. Zizania texana Hitchc.
Plants perennial; stoloniferous. Culms 1–2(5) m, decumbent, geniculate, floating or the distal portions emergent. Sheaths glabrous; ligules 4–12 mm, upper ligules caudate or acuminate; blades to 1 m long and 13(25) mm wide, glabrous. Panicles 16–31 cm long, 1–10 cm wide; branches unisexual. Staminate branches ascending or somewhat divergent; pedicel apices about 3 mm wide. Staminate spikelets 6.5–11 mm, ovate or oblong, acute to acuminate. Pistillate branches appressed or ascending; pedicel apices 0.5–0.9 mm wide. Pistillate spikelets 9–12.5 mm long, 1.2–1.8 mm wide, lanceolate, somewhat coriaceous, somewhat lustrous, with scattered short hairs, apices scabrous or hispidulous, awned, awns 9–35 mm; aborted pistillate spikelets 0.7–1.5 mm wide. Caryopses 4.3–7.6 mm long, 1–1.5 mm wide. 2n = 30.
Zizania texana grows only in the headwaters of the San Marcos River, in San Marcos, Texas (Terrell et al. 1978). It is officially listed as an endangered species in the United States.
4. Zizania latifolia (Griseb.) Turcz. ex Stapf
Plants perennial; rhizomatous. Culms 1–2.5(4) m, erect, rooting at the lower nodes, emergent. Sheaths glabrous, lower sheaths tessellate; ligules 10–15 mm, triangular; blades (30)50–100 cm long, 1–3.5 cm wide, abaxial surfaces smooth, adaxial surfaces scabrous. Panicles 30–50 cm long, 10–15 cm wide; branches unisexual or bisexual, lower branches with staminate spikelets, middle branches with staminate and pistillate spikelets, upper branches with pistillate spikelets. Staminate branches spreading; pedicel apices 0.2–0.5 mm wide. Staminate spikelets 8–12 mm, elliptic-oblong, margins ciliate, awned, awns 2–8 mm, scabrous; anthers 5–8 mm. Pistillate branches erect; pedicel apices 0.3–0.6 mm wide. Pistillate spikelets 15–25 mm, linear, veins scabrous, awned, awns 15–30 mm, scabrous. Caryopses about 1 cm. 2n = 30, 34.
Zizania latifolia is native to Asia, extending from northeast India and Russia through China and Myanmar to Korea and Japan. In its native range, it grows in the shallow waters of lakes and swamps, forming large patches.
The rhizomes and basal parts of the culms of Z. latifolia are edible, and become swollen when infected with the fungus Ustilago esculenta Henn. The infection also prevents the plants from flowering and fruiting. If infected plants were introduced into North America, the fungus might also infect the native species of Zizania and likewise prevent their flowering (Terrell and Batra 1982), a possibility that should be strenuously resisted. Plants of Z. latifolia should not be brought into North America. Many states do not permit importation of plants of Z. latifolia from another state without examination by a state-approved plant pathology laboratory.
New Zealand has designated Z. latifolia a prohibited plant because it “displaces all species by its dense growth, blocks drainage and access to water, and increases the chance of flooding. It forms dense colonies in swampy areas, thus affecting productive farm land” (Environment Walkato 2002–2007).