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Invasive noxious weeds & watershed restoration don't mix

Oregon Dept. of Ag advises land managers to watch for weeds as they plant seeds

The planting of desirable grasses and other vegetation is a key strategy in restoring watersheds for salmon and other threatened or endangered species in Oregon. But it will do no good if what is planted is infested with noxious weed seeds. The Oregon Department of Agriculture is using education as a means to ensure the right kind of seeds go into the ground this spring.

“We definitely believe in the importance of watershed restoration projects on both agricultural and non-agricultural lands,” says ODA Director Katy Coba. “We just need to make sure efforts are not compromised by the introduction of invasive weeds in those sensitive areas.”

From the two-acre landowner who plants from a 20-pound bag of seed to a federal agency land manager responsible for thousands of acres that may buy seed by the ton, using clean, weed-free seed is critical to repairing the land and enhancing Oregon’s watersheds.

“We already have some major weeds and don’t need any more from the planting of seeds,” says Tim Butler, manager of ODA’s Noxious Weed Control Program. Yellow starthistle, knapweed, and white top are examples of the kinds of weeds that can derail watershed restoration projects over time.

“Watershed restoration projects are designed to get a desirable plant species to establish on site areas to both compete with invasive weeds and provide fish and wildlife habitat ,” says Butler. “Perennial grasses you are trying to establish have a fibrous root system that holds the soil together and prevents erosion. But if something undesirable like knapweed gets a hold, it can dominate the site with a tap-root system that doesn’t hold the soil and can increase siltation in nearby streams.”

Oregon's first line of defense in integrated weed management is prevention. This includes having adequate laws in place to regulate seeds such as wildflower seed. In 2003, a visiting farmer from Australia detected a plant in Linn County called Paterson's curse, which is toxic to most livestock and one of Australia's major noxious weeds. ODA worked with the Oregon State Weed Board to get Paterson's curse placed on the state noxious weed list and took immediate steps for controlling the Linn County site as well as another site that was confirmed in Douglas County in 2004. Today, both sites are nearing 98 percent control. It took a change in the state’s seed law to regulate wildflower seed mixes,  which included the Paterson's curse, to help prevent a similar intrusion in the future.

Oregon’s history– both past and present– offers other examples of the unintended consequences of seed plantings that inadvertently included invasive noxious weeds.

In the late 1980s, to prevent erosion, the U.S. Forest Service used aircraft to drop grass seed on thousands of acres destroyed by fire in Northeast Oregon. Unfortunately, that seed was contaminated with yellow starthistle. The weed spread like a biological wildfire itself and became an expensive problem to deal with. Hopefully, the lesson has been learned. Efforts by federal agencies such as the Bureau of Land Management (BLM) this past year to restore rangeland destroyed by fire in southeastern Oregon involve replantings that are careful to not include weed seeds.

In the late 1990s, contaminated wheatgrass seed originating from California but sold by a Central Oregon seed dealer introduced yellow starthistle to several counties. As part of the construction of a new spillway at Ochoco Reservoir, a five acre site was seeded in 1997 with the tainted supply. When the site was monitored the following summer, starthistle was thriving. Workers had to hand pull hundreds of weeds. Officials say the damage caused by contaminated seed may be worse than if the site had not been seeded at all. Today, the site still needs to be monitored for any starthistle plants that might pop up.

An ounce of prevention is worth a pound of weed-free seeds, or more.

“It’s better to spend the dollars up front– before planting,” says Jim Cramer, director of ODA’s Market Access and Certification programs.

ODA provides regulatory oversight of seed dealers through sampling and testing of product as well as auditing of records. Some companies may end up facing a civil penalty for selling seed containing a prohibited noxious weed. But even the most reputable of companies can find themselves in trouble with weed seeds if they don’t intensively sample and test what they have. That’s where the education role comes in for ODA.

Purchasers of seed– especially those involved in restoration projects– need to make sure sampling and testing has been done prior to planting the seed. That goes for the farmer or rancher as well as the big agencies responsible for large tracts of land.

“Individual landowners may not be able to afford additional sampling and testing of the seed,” says Cramer. “But at a minimum, they can ask their supplier for the test reports and blending sheets. They should know the origin of their seed. Large agencies and municipalities have the opportunity to resample and retest the seed to minimize the potential of spreading noxious weeds in Oregon.”

Another indicator of seed purity is the label. Like any other product sold commercially, the label will tell the buyer what the package contains– or at least it is supposed to. Some weed seeds are not prohibited as part of a seed lot. But the information should appear on the label.

“We tell municipalities and individual landowners never accept seed that is not labeled,” says Cramer. “The label must state the variety and kind of each component in the bag including the weed seed amount by weight as well as any noxious weed that might be in there. The origin, purity, and germination for each component must be on the label.”

All this effort should be done before the planting of the seed. Once it is in the ground, any weed problems are much more costly in time, effort, and money. Restoration projects will continue. A weed seed planted today can undermine a project counted upon for tomorrow.

For more information, contact Bruce Pokarney at (503) 986-4559.

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