The mesquite — landowner's friend or foe?

The Pima called it "The Tree of Life." Ranchers call it something else entirely. It has overtaken more than 52 million acres of pastureland statewide. "It" is the Honey Mesquite tree.

We can blame mastodons and ground sloths for bringing the mesquite up from Argentina 50 million years ago. When the animals died off during the Ice Age, the mesquite retreated to flood plains and washes. Wildfires kept them contained. Then the buffalo came, taking over the role of the giant herbivores.

Finally, the perfect ally arrived in European livestock. Cattle devoured the grasses, eliminating wildfire fuel. They ate the mesquite, distributing the seeds along cattle trails. When the cattle were confined to fenced pastures, the grass had no chance due to overgrazing, but the mesquite thrived.

The mesquite is almost the perfect plant. It sheds its leaves to conserve moisture. Its seeds last for decades, and it has two root systems, which it can switch between rapidly. Usually, mesquites take water through roots that reside in the first three feet of soil. However, if needed, the mesquite can use its taproot to suck water from over 100 feet deep.

A quail takes cover among the branches of a mesquite tree. A quail takes cover among the branches of a mesquite tree. The Honey Mesquite can grow 20 feet high. Before man began killing it with chemicals and machines, mesquite usually grew as a single-trunked tree. Unfortunately, those attempts caused it many times to grow back as a multistemmed shrub, where it creates dense thickets that crowd out everything else. It's almost impossible to completely eradicate, as it can regenerate from a piece of root left in the soil. A bright side is the droppings from a mesquite thicket make excellent compost.

The mesquite is a legume. Its roots are hosts to nitrogen-fixing bacteria, so the tree actually helps enrich poor soils. The Pima would leave the trees in the middle of their fields to keep the soil healthy.

Wildlife uses the trees for shelter and food. In some areas 75 percent of a coyote's "undefined" diet in late summer is mesquite beans. Bees make honey from the yellow flowers that bloom in May.

One strategy for managing mesquite is the "mesquite savanna," where low densities of mature, upright trees are dotted throughout either native or pasture grasses. This provides habitat for both wildlife and livestock. Even in this scenario, the mesquite needs to be controlled. Through studies by A&M, one way to maintain the savannah would be a combination of low-intensity fires and Reclaim (clopyralid) at a quarter-pound per acre rate.

Native Americans relied on the tree for food, shelter, and medicine. The Cuchendados, Coahuiltecan, Tohono O'odham, Pima, Seri, and Mescalero Apache used it. Settlers turned to mesquite for food during droughts. Soldiers during the Civil War made coffee with the beans. In the 1870s mesquite gum was shipped east where candy makers used it for gumdrops.

The eight-inch pods can be ground into nutty tasting flour. Medical studies have shown that mesquite flour is effective in controlling blood sugar levels in diabetics. Mesquite gum, leaves, and bark have antiseptic qualities to soothe everything from ailing eyes to sore throats, headaches, and dysentery.

The mesquite's hard wood is used for furniture, fenceposts and homebuilding. Indians used it for tools and weapons. Mesquite woodblocks once paved San Antonio's downtown streets. It makes great firewood because it burns smokeless and slowly. It also adds that great taste to barbeque.

Mesquite could one day fuel vehicles. One ton of mesquite wood yields 214 gallons of ethanol. By comparison, corn yields about 124 gallons per ton.

Learning to live with the mesquite could bring many economic opportunities that could give it back the title "The Tree of Life."

El Camino Real Master Naturalists: http://grovesite. com/page.asp?o=tmn&s=ecrmn&p=204556

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2009-08-13 digital edition

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