The Mesquite Bosque

illustration of forest at base of mountain illustration of forest at base of mountain

Left image
An artist's rendering of forest at the foothills of the mountains

Right image
Tumacácori's mesquite bosque


How It Was

The mesquite's history and value to desert dwellers goes far back in time. Mesquite bosques (Spanish for small forests) reach their greatest development near desert rivers or where their long roots can reach ground water. This rich woodland plant community on the floodplain of the river provided the mission community with wood, medicine, and foods that were essential to life.

The tiny mesquite flowers, rich sources of pollen and nectar for wildlife, are crowded onto long spikes called catkins. Although the principal bloom normally occurs in spring after the winter rainy season, a second bloom of lesser intensity may occur in response to the summer monsoon rains.

When fertilized, the flowers form long green fruits that resemble string beans. These grow and mature through the summer months. The ripe beans are tan or streaked with red, and are sweet. A second harvest of mesquite beans is usually possible in the fall as a result of the summer bloom; this is why you sometimes see mesquite beans persisting on some trees well into winter.

The beans can be eaten at all stages of their growth. They were an important food for the O'odham, who ate them as a vegetable when green, and ground the pods into flour when ripe. They are favored by many animals, including hares, pocket mice, kangaroo rats, pack rats, and javelinas. Small bruchid beetles lay their eggs on mesquite beans so that the larva can bore through the pod and into the seed, where they pupate. The mature beetle then eats its way out of the seed and pod, leaving the little holes so often seen on mesquite beans.

Although other varieties of mesquite like honey and screwbean mesquite exist in the region, the velvet mesquite (Prosopis velutina) dominates the landscape of Tumacácori.

(text adapted from Ruth Greenhouse, Desert Botanical Garden
courtesy The Arizona Republic, May 13, 1988)


How It Is Now

The term mesquite bosque describes a closed canopy woodland dominated by mesquite trees on river flood plains. It is now a rare ecological community due to wood cutting, land use for development, and water pumping for human use, livestock grazing, and agriculture. Mesquite trees depend on the availability of ground water within a certain distance below the surface of the landscape in order to grow to heights sufficient to create a closed canopy.

Other species of trees that make up the top canopy of the mesquite bosque include velvet ash (Fraxinus velutina), netleaf hackberry (Celtis reticulata), and Arizona walnut (Juglans major). The understory is home to many shrubs including Wolfberry (Lycium spp.), greythorn (Ziziphus obtusifolia), Mexican elderberry (Sambucas mexicana), and catclaw acacia (Senegalia greggii). Among the many unique flowers and vines that live on the forest floor are pigeonberry (Rivina humilis), violet wild petunia (Ruellia nudiflora), virgin's bower (Clematis drummondii), passionflower (Passiflora mexicana), and indian root (Aristolochia watsonii).

This unique vegetative association located near the river makes the Tumacácori mesquite bosque home to a wide variety of insects, amphibians, reptiles, birds and mammals. In the Southwest, it is second only to the adjacent cottonwood-willow forest in the number of species of breeding birds that occupy it, making this area a wonderful destination for those who enjoy watching birds and other wildlife. Mesquite catkins, leaves, and seeds, as well as those of other associated plant species, are favorite foods of many insects, which then provide food to other animals. Mule deer and javelinas eat mesquite pods and rely on the shade provided by this critical semi-desert habitat. They, in turn, provide food for mountain lions. In addition to all of these characteristics, the mesquite bosque is also an essential migration corridor for birds and other animals.

Humans also enjoy the gifts of the mesquite bosque. This floodplain system provides clean water and protection from flooding and erosion. The vegetation both filters and slows the flow of runoff from rainfall into the Santa Cruz River, allowing clean water to filter through the soil, recharging the aquifer which is used for drinking water and irrigation.

Visitors can get an up-close look at mesquite bosque by exploring the Juan Bautista de Anza National Historic Trail from the Tumacácori mission grounds to the Santa Cruz River.


Forests of the National Park System

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    Last updated: July 23, 2020

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