The invasive salt cedar, or tamarisk, hogs our scarce water supplies and threatens to overwhelm our floodplains and wetlands.
by Jay W. Sharp
Since its introduction more than a century ago, salt cedar, or tamarisk, has become an unwelcome guest, not only along the Rio Grande in south-central New Mexico but also along waterways and around lakesides throughout the Southwest. Indeed, it is so unwelcome in New Mexico that our state legislature appropriated funds for a "Lower Rio Grande Salt Cedar Control Project," which is aimed specifically at dis-inviting the plant as well as other noxious botanical invaders.
Salt cedar, or tamarisk, thickets crowding the Rio Grande, just north of Las Cruces. (Photos by Jay W. Sharp)
Salt cedar reminds you of an intrusive mother-in-law, who arrives just as you and your spouse are having a serious discussion about dirty socks on your bedroom floor, grubby dishes next to your kitchen sink, empty beer cans on your coffee table, a wet shot glass on your new and expensive end table, a new Browning over-and-under shotgun charge on your credit card, and a flirtation at your recent neighborhood get-together.
The salt cedar — encompassing several species now on the loose in the United States — has spread as an intrusive plant, helping itself to our dwindling water supply, poisoning the soils of our lands, setting the stage for wildfire, usurping riparian growing areas from our native plants, degrading the environment for our wildlife, changing the character of our drainages, and increasing the potential for flooding and sedimentation. Indeed, government agencies rank it as one of the 10 worst noxious weeds in the United States.
And when it comes, it comes to stay. Indeed, as Kris Zouhar wrote in a US Forest Service publication, "In New Mexico, individual shrubs 75 to 100 years old have not yet shown signs of deteriorating due to age."
Native to the arid Middle East, the salt cedar — a lacy-looking large shrub or shrub-like tree typically 10 to 15 feet in height in our part of the world — was imported into the arid Southwest around the 1830s. It would, its importers apparently thought, serve to decorate yards and parks, control erosion, and check spring winds. Promptly escaping its human hosts, it now grows in impenetrable thickets along the banks of rivers, streams, wetlands, reservoirs and irrigations ditches, with its new plants shooting up as much as 10 feet in a single season under favorable conditions. It actually thrives in alkaline and saline soils.
Dense salt cedar growth.
Its slender curving trunk and its older branches, according to Oklahoma State University experts, have a reddish-brown bark that becomes "grooved and wrinkled as the limbs age," dying and becoming potential fuel for wildfire. New branches have a smoother, reddish-brown bark.
The salt cedar puts down a deep and extensive root system, according to Zouhar. Its primary root probes downward 10 or 12 feet, with little branching, reaching for moisture. Then it sends out a profusion of secondary root branches, which may extend laterally for 25 feet or more, well beyond the canopy of the plant. Salt cedar roots within a single thicket may be densely intertwined.
The salt cedar's leaves give the plant a distinctive character. Greenish, scale-like, narrow and pointed, they measure only about 1/16th of an inch in length. Although they resemble the leaves of our native evergreen junipers or cedars through the spring and summer, the salt cedar leaves turn golden and drop off in the autumn. The leaves, says the US Department of Agriculture's Natural Resources Conservation Service, have salt-secreting glands on their undersides. These serve, during the growing season, to secrete the salt from moisture that passes through the salt cedars rooted in saline soils. The tops of its leaves may become glazed with secreted salt. When they drop, they can leave a salty litter of leaves on the ground's surface and then in the top soil — an annual event. They also become potential fuel for wildfire.
The plant blooms from spring into late summer or early fall, producing clusters of white to pink flowers at the tips of its branches. Pollinated by bees and other insects, the flowers, about 1/16th of an inch in length, have five distinct petals. At full maturity, a flower forms a capsule packed with tiny seeds.
A mature salt cedar's blooms produce perhaps half a million seeds, each about 1/25th of an inch in length, with a tuft of fine hairs. A seed may ride on our Southwestern winds for miles, becoming a primary agent for the plant's dispersal. It may also float in nearby stream waters to a new home. It can hitch a ride in the coats of animals or even on the clothes, boats and trailers of humans. Absent transportation, it may simply fall to the ground's surface, forming a dense litter. "One hundred seeds per square inch have been produced within a salt cedar forest," according to a fact sheet produced by the University of Nevada at Reno.
The salt cedar has a tenacious facility for propagation and survival. Under favorable conditions, a high percentage of salt cedar seeds — produced throughout the growing season — may germinate within hours, according to Zouhar. They may, in fact, form a veritable carpet of seedlings beneath the plant canopy. Additionally, says Zouhar, a mature salt cedar's roots may give birth to new shoots adventitiously, or essentially randomly, beyond the plant's canopy. If a salt cedar's above-ground portions fall to machine, ax or fire, the plant may simply produce new sprouts from its root crown. If it loses a limb to, say, flood waters, that limb may become an agent for expansion, for if it becomes buried by moist sediments, it can develop its own roots and sprout, growing as an independent plant.
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