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Plant Profile

Texas Wild Rice (Zizania texana)

This shot shows the plant growing in a flowing river. Photo Credit: San Antonio Botanical Garden

Global Rank: G1 - Critically Imperiled
Legal Status: Federally Endangered
Family: Poaceae
State: TX
Nature Serve ID: 155192
Lifeform: Graminoid
Date Inducted in National Collection: 04/01/1990

Description:

Texas wild rice is an aquatic herbaceous perennial which can be found growing only in the cool, clear waters of the San Marcos River in Texas. This species was so abundant in the 1930's that the local irrigation company considered it difficult to keep this plant from clogging its ditches. In striking contrast, this species is now listed as federally endangered (USFWS 1978), with only a few populations known in the wild. A main cause of this decline is the fact that water has been pumped out of the Edwards Aquifer to supply water for agriculture, industry, and human use. This directly effects the spring flow of the San Marcos River, which this wild rice depends upon. Lowering of the river water levels is a major threat to the survival of this species. Texas wild rice is related to commercially grown wild-rice, and therefore a potentially invaluable resource of hardy genetic stock.

Where is Texas Wild Rice (Zizania texana) located in the wild?

Habitat:

This aquatic grass is found in the San Marcos River, forming large clones or masses of clones firmly rooted in shallow gravel beds near the middle of the river. This plant is adapted to and requires fast-flowing, high quality water at a constant year-round temperature. Critical habitat was designated in 1980. (WWF 1990; USFWS 1980)

Distribution:

Upper San Marcos River in Hays County, Texas

States & Provinces:

Texas Wild Rice can be found in Texas

Which CPC Partners conserve Texas Wild Rice (Zizania texana)?

National Laboratory for Genetic Resource Preservation (USDA-ARS)

Not Sponsored

Conservation Actions

Assigned 08/15/23

Lady Bird Johnson Wildflower Center

Not Sponsored

Conservation Actions

Assigned 10/30/24

CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.

Conservation Actions

Tina Stanley

04/22/2024

Lady Bird Johnson Wildflower Center (LBJWC) participated in a series of studies on the factors affecting sexual and asexual reproduction of this species. The species is primarily outcrossing with short-lived pollen, which limits sexual reproduction. Asexual reproduction by tillers is also likely important in nature. Reproduction occurs at all times of year but exhibits seasonal variation.

LBJWC participated in a survey of culm density and status. Mean number of culms was 8.03/0.065m^2 (approximate area occupied by a single plant), and 1% of culms were producing seeds.

Center for Plant Conservation

12/02/2021

Texas wildrice (Zizania texana Hitchc.), an endangered macrophyte, is endemic to the San Marcos River and Spring Lake in Hays County, TX. Its population declined dramatically between 1940 and 1967. In a reintroduction program that was initiated by the Southwest Texas State University in 1992, plants were transplanted into five microhabitats at a density of 10 plants/m2. Seasonal monitoring identified an initial increase in plant size followed by high mortality in three of five sites. Data suggests that stem density is a good indicator of future transplant success and that current velocity is an important environmental factor associated with transplant success. However, herbivores have continually clipped reproductive culmns below the water surface. This limits transplants to clonal reproduction.

10/09/2020

Christina Walters and Darren Touchell at NSSL are working on cryopreservation techniques of Texas wild rice. (CPC Annual Report, 1998)

10/09/2020

Dr. Mike Antolin of Colorado State University in Fort Collins, Colorado has been doing studies on the genetics of the wild and captive populations at SWT and SMNFH&TC.

Nature Serve Biotics

05/02/2017

Endemic to the upper few km of the San Marcos River in south-central Texas, where it was locally abundant as recently as the the 1950s. It is now reduced to a precariously small population covering about 1200 square meters on an urbanized segment of the river. This remnant population rarely flowers or produces seed in the wild. The decline of this grass, which is narrowly adapted to high quality, aquifer-fed waters, is the result of drastic draw-downs in the aquifer level to support human population growth in the area, combined with past dredging and vegetation removal, damming, increased siltation and sewage loads, trampling and removal by recreationists, and herbivory by native and introduced waterfowl and by the non-native nutria. Efforts to establish new populations off the San Marcos River using cultivated plants have not been successful.

Cindy Barrett

01/01/2010

Groundwater pumping of Edwards aquifer Pollution from vegetation management Stream modification by damming Recreation--including swimming and boating in and around the populations Nutria (aquatic rodents) eating stalks

Cindy Barrett

01/01/2010

140 clumps in one unprotected population 100 plants introduced at Spring Lake, 90 surviving and doing well, starting inflorescence development population maintained on the Southwest Texas State University campus in an outdoor cement raceway Current distribution of wild rice extends from the uppermost part of the San Marcos River just below Spring Lake dam and throughout the critical habitat down to an area slightly below the wastewater treatment plant, except for the river portion between the Rio Vista railroad bridge and the dam above Cheatham Street.

Cindy Barrett

01/01/2010

Research has been conducted by the Department of Biology, Southwest Texas State University and The San Marcos National Fish Hatchery and Technology Center. Dr. Mike Antolin of Colorado State University in Fort Collins, Colorado has been doing studies on the genetics of the wild and captive populations at SWT and SMNFH&TC. Christina Walters and Darren Touchell at NSSL are working on cryopreservation techniques of Texas wild rice. (CPC Annual Report, 1998)

Cindy Barrett

01/01/2010

In 1998, Paula Powers reported that she was working in a collaborative restoration project with Dr. Robert Doyle, North Texas State University, Denton. This project involves identifying potential restoration sites and establishing methods for transplanting Texas wild rice into the San Marcos River.

Cindy Barrett

01/01/2010

Response to disturbance Seed dispersal and seedling recruitment Genetic analysis Public education campaign Restore/maintain the historic flow of the San Marcos River