Manihot walkerae
Manihot subspicata
Texas tapioca, Walker's manihot
palo mulato, spike manihot
decumbent to ascending (often growing through associated vegetation), terete when young;
nodes not swollen;
leaf and stipule scars not elevated.
lax (often leaning on other vegetation), terete when young;
nodes not swollen;
leaf and stipule scars not elevated.
stipules lanceolate, entire;
petiole 1–7 cm;
blade peltate, 3–5-lobed, lobes with rounded secondary lobes distal to middle or with 2 pairs of rounded secondary lobes of nearly equal width proximal and distal to middle, median lobe 2–7 cm, margins neither thickened nor revolute, entire, apex cuspidate, surfaces glabrous, abaxial smooth.
stipules lanceolate, entire;
petiole 2–10 cm;
blade basally attached to subpeltate, 5-lobed, lobes with acute secondary lobes near base, median lobe 2–10 cm, margins thickened and revolute, remotely serrate, apex acute to acuminate (bristle-tipped), surfaces glabrous, abaxial smooth.
axillary, subspicate racemes, 5–10 cm.
terminal, racemes, 25 cm.
staminate 1–3 mm;
pistillate 15 mm in fruit, downcurved.
staminate 1–5 mm;
pistillate 10–20 mm in fruit, downcurved.
calyx tubular, base gibbous, midsection constricted, 10–20 mm, lobes erect or spreading;
stamens 6–8.
calyx campanulate to conic, 8–13 mm, lobes reflexed;
stamens 10.
1 cm, verrucose-rugose, not winged.
1.5 cm, smooth, not winged.
globose, 8–9 mm.
oblong, 10 mm.
Manihot walkerae
Manihot subspicata
Manihot walkerae is a globally endangered species known from Duval, Hidalgo, and Starr counties and nearby Tamaulipas, Mexico. It is restricted to areas of sandy or gravelly calcareous soils overlying caliche or limestone bedrock. An estimated 95 percent of its habitat in the United States portion of the lower Rio Grande Valley has been converted to largely agricultural uses (www.natureserve.org).
The stamen number (6–8) of Manihot walkerae is notable relative to that of other species in the genus, which typically have 10 stamens per staminate flower.
Manihot walkerae is in the Center for Plant Conservation's National Collection of Endangered Plants.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Although D. J. Rogers and S. G. Appan (1973) characterized leaf blades of Manihot subspicata as peltate, seldom are leaves unambiguously so. Typically, just the thickened margins of lateral lobes are confluent across the distal end of the petiole. Though relatively common in northern Mexico, M. subspicata is known in Texas only from the vicinity of Lake Corpus Christi (Jim Wells and Live Oak counties); whether native or introduced there is unresolved. In Mexico, M. subspicata appears to be tolerant of disturbance, frequently colonizing roadsides and similar habitats.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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