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Arizona
Range Grasses Back to the Table of Contents
Growth habit: A coarse perennial bunchgrass 1 to
2 feet tall, growing from a coarse scaly rootstock. Stems spread out
at the base, then curve inward at the top, giving each bunch a pointed
appearance. Stems are not woolly. Tobosa grows over a wide range of
climatic conditions and shows considerable variation in form, depending
on conditions under which it grows. In the drier portion of its range
it becomes very coarse while at higher elevations, where moisture is
more plentiful, the plants are much smaller and finer.
Occurrence Locally common in Yavapai, Gila, Mohave, Graham, Yuma,
Cochise, Santa Cruz, and Pima counties at elevations from 2,000 to 6,000
feet. In the lower or more southern parts of its range, tobosa grows
on fine-textured soils in swales that receive runoff water. Farther
north or at the higher elevations it occurs typically in fine-textured
soils on dry rocky hillsides or mesa tops. Forage Value The forage value of tobosa grass varies from good during the summer months when it is green, to very poor during the winter months, when it becomes harsh and wiry and loses most of its value as forage. Forage value during the summer is also variable, depending upon the amount of old growth remaining on the plants. If old growth is profuse, animals will not graze the plant unless forced.
Tobosa appears fairly resistant to grazing. However because
of its coarseness and low palatability it is usually rather lightly
utilized. It should be used during the summer when it is green and has
its highest forage value. A rotation developed in southern New Mexico
utilizes tobosa grass areas during the summer and black grama during
the winter. This has maintained the black grama range in top condition
and has not materially injured the tobosa. Best quality tobosa grass is obtained by eliminating as
much of the old growth as possible, which may be done by heavy grazing,
burning or mowing. Heavy grazing will keep the old growth down, but
may injure the stand because of close use during the growing season,
trampling, or both. Burning every third or fourth year during late winter
or early spring has been satisfactory on many areas.
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Cooperative
Extension,College of Agriculture & Life Sciences, The University of
Arizona