Walker's manioc

Distribution map of Walker's manioc

Distribution

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Distribution map of Walker's manioc (Manihot walkerae ).

Scientific Name
Manihot walkerae
Other Scientific Names
None
Other Common Names
Walker’s manihot, Texas tapioca
Status
Federally and State Endangered
Global Rank
G2
State Rank
S1

Global Location

Walker’s manioc grows in southern Texas in Duval, Hidalgo, and Starr counties as well as the state of Tamaulipas in northern Mexico.

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Description

Walker’s manioc is a perennial plant, which dies back during dry periods or following a freeze. The fleshy, underground root stores water and nutrients, and produces new stems each year. The plant has a dull almond odor caused by the presence of hydrogen cyanide in all parts of the plant. Otherwise reclining, the stout, but supple stems will often use other nearby vegetation for vertical support. Leaf stalks attach to the middle of each leaf blade, instead of the more common attachment at the edge of the leaf blade. Leaves grow up to 14 cm long by 11 cm wide, and usually have three to five deep, rounded lobes. The elaborate lobes vaguely resemble a fiddle in outline. The white, five-lobed flowers arise from the same point as a leaf off of the main stem. Female, fruit-producing flowers occur separately from male, pollen-bearing flowers. Immature fruits resemble a small, white-striped, green marble. Mature fruits dry and break open to disperse three seeds.

Walker’s manioc has white, five-lobed flowers. These flowers are male, pollen-bearing flowers (which occur separately from female, fruit-producing flowers).

Walker’s manioc has white, five-lobed flowers. These flowers are male, pollen-bearing flowers (which occur separately from female, fruit-producing flowers).

Credit: Jackie Poole - Texas Parks & Wildlife Dept.

Walker’s manioc has elaborate leaves, usually with three to five deep, rounded lobes. This leaf has three larger lobes and two smaller lobes.

Walker’s manioc has elaborate leaves, usually with three to five deep, rounded lobes. This leaf has three larger lobes and two smaller lobes.

Credit: Jackie Poole - Texas Parks & Wildlife Dept.

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Similar Species

Jicamilla (Jatropha cathartica) has somewhat similarly shaped leaves, but the leaf edges are saw-toothed instead of smooth. Also, jicamilla has red flowers, instead of white. Balsam gourd (Ibervillea lindheimeri) is a vine with thinner stems, yellow flowers, and red fruit. Although it uses other plants for support, Walker’s manioc is not a vine. Another manihot species (spiked manihot) occurs in Texas, but not in the immediate area of Walker’s manihot. Spiked manihot (Manihot subspicata) lobes are narrow and fruits are oval.

Balsam gourd has yellow flowers.

Balsam gourd has yellow flowers.

Credit: Bill Carr

Balsam gourd is a vine with red fruit.

Balsam gourd is a vine with red fruit.

Credit: Bill Carr

Spiked manihot usually has three to five deep, narrow lobes.

Spiked manihot usually has three to five deep, narrow lobes.

Credit: Carlos Velazco

Spiked manihot has oval fruits.

Spiked manihot has oval fruits.

Credit: Carlos Velazco

Jicamilla has red flowers and saw-toothed leaf edges.

Jicamilla has red flowers and saw-toothed leaf edges.

Credit: Bill Carr

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Floral Characters

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Leaf Characters

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Habitat

Walker’s manioc grows in thorn shrublands on shallow, sandy soils often over hardened caliche.

Habitat of Manihot walkerae. The stems often use other nearby vegetation for support and growth. The image shows lotebush, acacia and even barbed wire being used as vertical support.

Habitat of Manihot walkerae. The stems often use other nearby vegetation for support and growth. The image shows lotebush, acacia and even barbed wire being used as vertical support.

Credit: Dana Price - Texas Parks & Wildlife Dept.

Life Cycle Events

Flowering occurs from April to September.

Survey Season

Walker’s manihot dies back during droughts or after a freeze, but during warm months with typical precipitation, it is recognizable by its distinct leaves.

Comments

Seed dispersal, specifically explosive seed dispersal, can be one of the fastest movements in plants. Explosive seed dispersal is seen in several different groups of plants, including impatiens. In Walker’s manioc, the fruit splits open and forcibly ejects the seed up to several meters from the parent plant. This mechanism can substitute or bypass other types of dispersal like animals, wind, or water.