Search / Plant Profile / Manihot walkerae

Plant Profile

Walker's Manihot (Manihot walkerae)

The white, 5-lobed flower of Walker's manoic. Photo Credit: San Antonio Botanical Garden

Global Rank: G2 - Imperiled
Legal Status: Federally Endangered
Family: Euphorbiaceae
State: MX, TX
Nature Serve ID: 160439
Lifeform: Forb/herb
Date Inducted in National Collection: 02/25/1988

Description:

Manihot walkerae is an endangered plant in South Texas and parts of Mexico (USFWS 1993). It is related to other Manihot species which are grown in Third World countries in order to provide cassava, an important source of starch for millions of people. The roots must first be boiled in order to extract poisonous, possibly fatal, acids. Tapioca is a product derived from cassava. Manihot walkerae is the most cold hardy of the Manihots. Crossing this species with others may increase the growing range of those Manihots used as a food source. Manihot walkerae may also contain important disease resistant genes. (USFWS 1993). Separate female and male flowers occur on the same plant, with all flowers blooming from April to September following rain. Male flowers occur on elongated stems and are white with light purple streaks. They have five lobes, are nearly 1/2 inch long, and are shaped as tubes. Female flowers, much smaller than male flowers at only 3/8 of an in long, occur at the base of the long stalks of the male flowers. (Texas Parks and Wildlife 2002)

Where is Walker's Manihot (Manihot walkerae) located in the wild?

Habitat:

Found in the Tamaulipan Biotoic province, on mesic upland in or near dense stands of native brush, which create a microclimate of shade, protection from trampling/grazing, and lower temperatures,.

Distribution:

Known from the Lower Rio Grande Valley of Texas (Hidalgo and Starr counties) and northern Tamaulipas, Mexico. (Texas Parks and Wildlife 2002)

States & Provinces:

Walker's Manihot can be found in Mexico, Texas

Which CPC Partners conserve Walker's Manihot (Manihot walkerae)?

San Antonio Botanical Garden

Conservation Actions

Tina Stanley

08/29/2022

As of August 2022, San Antonio Botanical Garden holds this species in living collection and has conducted propagation research.

09/19/2020

Also, Chris Best at the U.S. Fish and Wildlife Service's Santa Ana Wildlife Refuge has investigated the effects of using mechanical and chemical scarification, aeration, seed storage time, and growth regulators

09/19/2020

09/19/2020

Seed from core collection plants are being stored on site for research.

09/19/2020

Currently the San Antonio Botanical Garden maintains a core collection of Manihot walkerae from plants at UT-Austin in a cold frame and greenhouse. Some plants were planted into a test plot and demonstration garden for both research and educational reasons

09/19/2020

Walker's Manihot has been under cultivation at the University of Texas at Austin (UT-Austin) since 1940

Nature Serve Biotics

05/02/2017

A regional endemic of southern Texas and northern Mexico, this species was thought to have been extirpated from the U.S. until a single surviving plant was discovered in 1990. Several additional occurrences have since been found (1995) on U.S. Fish and Wildlife refuge tracts. 2 surviving populations were recently reverified (1993) in Mexico; 1 with about 10 plants, the other with about 100. Over 95% of this species' native brushland habitat has been cleared for agriculture, grazing and development. Remaining native habitats exist as fragments, and are vulnerable to accidental herbicide application, overgrazing, and other threats.

Cindy Barrett

01/01/2010

The major threat to Walkers manioc is the destruction and fragmentation of native brush and grassland habitats where it is currently found. As of 1993, when the recovery plan for this species was written, it was estimated that over 95% of the habitat tha

Cindy Barrett

01/01/2010

Found in four locations in Hidalgo and Starr Counties in Texas. One is located on private land, and contains only one plant, the other three are located in the Lower Rio Grande National Wildlife Refuge. (Texas Parks and Wildlife 2002) Two populations are known from northern Tamaulipas, Mexico. (USFWS 1993)

Cindy Barrett

01/01/2010

The San Antonio Botanical Garden conducted a germination study using an environmental growth chamber at Trinity University. Treatments included heat stratification, as well as, mechanical and acid scarification. For the first time, Manihot seeds germinated under cultivation, giving insight into breaking seed dormancy through heat stratification. Also, Chris Best at the U.S. Fish and Wildlife Service's Santa Ana Wildlife Refuge has investigated the effects of using mechanical and chemical scarification, aeration, seed storage time, and growth regulators.

Cindy Barrett

01/01/2010

Walkers manioc has been under cultivation at the University of Texas at Austin (UT-Austin) since 1940. Currently the San Antonio Botanical Garden maintains a core collection of Manihot walkerae from plants at UT-Austin in a cold frame and greenhouse. Some plants were planted into a test plot and demonstration garden for both research and educational reasons. Seed from core collection plants are being stored on site for research. In cooperation with the U.S. Fish and Wildlife Service, Manihot plants and habitat existing on U.S. sites are being voluntarily protected by private landowners. Mexico populations are being monitored by a Mexican botanist, Fransisco Gonzalez Medrano, under a U.S.-Mexico cooperative agreement with the U.S. Fish and Wildlife Service. (USFWS 1993)

Cindy Barrett

01/01/2010

Monitoring and surveys Pollination biology Response to disturbance Seed dispersal and seedling recruitment Habitat characterization Genetic analysis Germination requirements