Federal and State Listed Species of Texas:
Texas wild-rice

Distribution

Current

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Distribution map of Texas wild-rice (Zizania texana).

Scientific Name
Zizania texana
Other Scientific Names
None
Other Common Names
None
Status
Federally and State Endangered
Global Rank
G1
State Rank
S1

Global Location

Texas wild-rice is only known from the upper two miles of the San Marcos River in Hays County, Texas.

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Description

Texas wild-rice is a clumping perennial grass that roots underwater in riverbeds. The 1-2 m long stems bend, flowing parallel to the current, but the upper stem can bend back upward, above the water surface. The linear leaves are narrow (usually 3-25 mm wide), to 200 cm long, and a prominent vein running down the middle of the blade. Male and female flowers occur separately on side branches of a 16-31 cm long flowering stalk. The male flowers dangle off the lower side branches of the flowering stalk, while the female flowers are produced on the stiffly erect upper side branches. As is typical of grasses, flowers are quite small (6.5-12.5 mm long, 1.2-2 mm wide) and inconspicuous. Male flowers bear pollen, are oblong to egg-shaped, and are slightly pointed at both ends. Female flowers produce seed, and the flowers are topped with a very thin, 9-35 mm long bristle. Texas wild-rice seeds are cylindrical, 4.3-7.6 mm long, 1-1.5 mm wide, and either black, brown or greenish.

The upper stems of Texas wild-rice can emerge above the water surface. The male and female flowers occur separately on side branches of a flowering stalk. The male flowers dangle lower down the flowering stalk than the rigid female flowers.

Credit: Jackie Poole - Texas Parks & Wildlife Dept.

Texas wild-rice roots underwater, and the stems bend, flowing parallel to the current. The leaves have a prominent main vein running down the middle of the blade.

Credit: John Thomaides

Texas wild-rice flowers are quite small. Female flowers are topped with a very thin, long bristle and seeds are cylindrical (shown in the upper right of the illustration overlapping the bristle of the female flower).

Credit: USDA-NRCS PLANTS Database / Hitchcock, A.S. (rev. A. Chase). Manual of the grasses of the United States.

Similar Species

Stems of giant cutgrass (Zizaniopsis miliacea) usually emerge from the water and grow to 4 m long. The male and female flowers occur on the same branches, with the female flowers closer to the stem’s tip than the male flowers. Eel grass (Vallisneria spiralis) and Illinois pondweed (Potamogeton illinoensis) both occur with Texas wild-rice and appear similar, but neither have the strong vein which runs down the middle of the Texas wild-rice blade.

Illinois pondweed can be identified by its oval to tear-drop shaped leaves, as opposed to the longer, linear leaves of Texas wild-rice.

Credit: Bill Carr

The male and female flowers of giant cutgrass occur on the same side branches of the flowering stalk.

Credit: Bill Carr

Giant cutgrass roots in shallow waters of wetlands, but generally holds its leaves above the water surface.

Credit: Bill Carr

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Floral Characters

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Leaf Characters

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Habitat

Texas wild-rice grows in gravelly or coarse sandy soils in clear, cool, fast-flowing waters of spring-fed rivers.

Habitat of Texas wild-rice.

Credit: Wyatt McSpadden - Courtesy of the Edwards Aquifer Authority.

Life Cycle Events

Flowering occurs from spring to summer, but flowering has been observed throughout the year.

Survey Season

Texas wild-rice can be identified year-round.

Comments

Rare in both extent and distribution, Texas wild-rice is threatened by the factors associated with its urban location near the headwaters of the San Marcos River. Texas wild-rice must live with continual habitat alteration, non-native species introductions, pollution, and recreational impacts. Although it has been shown that the areal coverage of the Texas wild-rice populations has increased over the last 35 years, the population has simultaneously decreased in overall range.