Tamarisk (or salt cedar) infestations are yet another example of what happens when people think their back yards are not connected to the natural world. Tamarisk is the name of a family of pretty flowering bushes or small trees from Eurasia. They were first introduced to the East coast sometime in the 1820's, and later found a niche in the American west. They escaped from gardens and soon took over flood plains and river banks. They often have enormous taproots which can suck up hundreds of gallons of water a day. Whole lakes have dried up due to the tamarisks on their shores.
Besides hogging groundwater, tamarisks exude salty moisture from their leaves in the morning and evening. As the leaves fall, they form a salty layer on the soil, making it nearly impossible for native plants to survive.
When small, these trees can sometimes be removed with a shovel and some loppers. If you're really lucky, you can just pull them out by hand. However, most all the upper root mass needs to be removed to prevent re-sprouting. When they're too big to pull, cut down the trees, leaving the stumps close to the ground. Immediately drive 4 or 5 holes into the stumps and apply undiluted Roundup® Weed & Grass Killer Concentrate Plus. Be careful removing the tree debris, since small pieces can break off and re-sprout. In places where the trees are very close to water, some people have had success cutting them down below the root crown.
Tamarisks have trouble becoming established in undisturbed areas. So you'll want to plant something desirable (and non-invasive) as soon as you can. You can treat the soil with one of several soil conditioners to reduce the salt left from the tamarisk. Ask your county extension office for information on the soil treatment that's best for your area. Amending your soil with organic material, such as Miracle-Gro® Organic Choice® Garden Soil, can help provide nutrients and better drainage. When your soil is ready, there are plenty of beautiful landscaping shrubs and small trees to choose from that are suitable for your area.
Article by Penny Wilson. Penny is a gardening writer who specializes in California native plants