Extension Service Garden Hints

Wildflower mixes may include unwanted surprises

CORVALLIS, Ore. - Like ready-mixed, all-in-a-box "gourmet" meals, wildflower seed packets seem to promise spectacular results with greatly reduced effort. There's no need to research long lists of ingredients or spend time shopping for them when time is what you don't have – much less figuring out later how they all go together. Wildflower seed mixes sound like the answer to a busy gardener's prayer.

But your visions of an instant flower meadow may turn into a headache if you aren't careful.

"Not only might some of the species listed in the contents be known invasive plants in Oregon, but the packet might also contain weed seeds that are not listed," said Susan Aldrich-Markham, agronomist with the Yamhill County office of the Oregon State University Extension Service.

"In addition," she said, "it is not unusual for ornamental plants or even native plants from other regions of the United States to become noxious weeds in Oregon, where the growing conditions are good and the natural enemies have been left behind."

In an unpublished study carried out at the University of Washington a few years ago, an undergraduate student researcher grew the contents of 19 wildflower seed mix packets. All 19 contained from three to 13 species that were identified as being invasive in some part of North America. Worse, eight plants were identified as noxious weeds in at least one state or Canadian province.

Tim Butler, manager of the Oregon Department of Agriculture Noxious Weed Control Program, said there are "some examples here in Oregon where we believe that noxious weeds have found their way into wildflower mixes.

"One example is yellow toadflax, (Linaria vulgaris), which is on the state noxious weed list," Butler said. "Another plant, Paterson's curse, (Echium plantagineum) showed up in Linn County in 2003 in association with wildflower plantings in field borders. This weed is a major problem in Australia where it is making a $30 million a year impact and affects range/pasture lands and livestock production."

Paterson's curse was later added to Oregon's noxious weed list.

If you are really short on time but nevertheless want to have an abundant medley of wildflowers growing next summer, the safest course is to buy seed packets of individual wildflowers. That way you can be sure of what you're planting while you customize your own mix.

If you still decide to buy a seed mix, think ahead now to avoid trouble next summer. Aldrich-Markham recommends that home gardeners take the following precautions.

First, buy from a local seed company. The wider the distribution area for seed packets, the more likely they are to contain species that are inappropriate for certain areas.

Second, check to be sure the packet actually lists the seeds it contains. Not all seed mix packets do. If there are plants listed you aren't familiar with, take a few minutes to check them out in a standard gardening reference or on the web.

To learn more, OSU Extension has noxious weed publications with photos on-line:

EC 1419

EM 8776

EC 1563

The Oregon Invasive Species Council lists the "100 worst invaders," including 20 land plants, at its website http://oregon.gov/OISC.

To look at the Oregon noxious weed list, go to http://egov.oregon.gov/ODA/PLANT and click on Noxious Weed Control.

On the general subject of invasive plants, see The Nature Conservancy's website on The Global Invasive Species Initiative at http://tncweeds.ucdavis.edu.

For more about native plants in Oregon, see http://www.npsoregon.org, the website for the Native Plant Society of Oregon.

By: Davi Richards
Source: Susan Aldrich-Markham, Tim Butler

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