Friday, April 9, 2010

Will it Be a Weed?

Jane Paterson has a plant named after her. Unfortunately it’s a noxious weed; the plant is called Paterson’s Curse. Ms. Paterson was an early settler in Australia. She brought seeds from Europe to beautify her garden. This plant was well adapted to Australia and has become one of that country’s worst weeds. Paterson’s curse has shown up twice in Oregon: in a pasture in Douglas County and in a field border planted to wildflowers in Linn County. It was thriving at both sites before the Oregon Department of Agriculture stepped in to eradicate it.

Not all our noxious weeds have escaped from gardens, but the list of Oregon weeds that were introduced on purpose is long and growing: English ivy, Scotch broom, Japanese knotweed, Portuguese broom, Jubata grass, yellow flag iris, Giant hogweed, orange hawkweed, kudzu, Spanish heath, yellow floating heart, Himalayan blackberry, seeded butterfly bush, gorse, spurge laurel, old man’s beard. . .

So you’d like to try a new plant, but you don’t want to make the same mistake as Ms. Paterson. How do you know if a plant will become a weed?

Researching a few simple questions when choosing plants can minimize the risk.
1.) Is it a weed anywhere else?
If it is, beware. The characteristics that make it weedy in one place will likely cause it to be weedy in any place with favorable conditions. Next, find out:
2.) How does it spread?
3.) Where does it thrive?
4.) Would it be difficult to control?
5.) Is there any possible negative outcome from planting it?

Plants likely to become invasive generally produce lots of seeds that spread by wind or birds. They often thrive in a variety of habitats with or without competition from other plants. Usually they are difficult to control and have a down side, like thorns, poisonous sap, or a tendency to contaminate crops. Beware of plants that fit these patterns.

Let’s try these quick & dirty screening questions with a few plants you are familiar with:
1.) Daffodil – Not considered a weed anywhere; produces very few seeds; naturalizes but doesn’t out-compete other plants; control isn’t an issue; no drawbacks, plus they are beautiful. =Good plant.
2.) Himalayan Blackberry – Weedy in many places in the world; produces lots of seeds which are spread by birds and other wildlife; lives just about anywhere and out-competes native vegetation; difficult to control and their thorns are nasty. =Noxious weed.
3.) Blue Spruce – Not a weed anywhere; not a lot of seeds; grows where it’s planted, if you take care of it; no control issues and no dark side. =Good plant.
4.) Seeded Butterfly Bush – Zillions of tiny seeds, competes with native plants; weedy in New Zealand and Europe. =Noxious weed. (Note that the new seedless varieties coming on the market now should eliminate the invasiveness of this plant. Yeah!)
5.) Tree of Heaven – prolific seeder; grows just about anywhere; considered a weed in many places (though not yet an official State noxious weed in Oregon); difficult to control. Warning! Warning! Warning! =Not a good choice.

A little research and careful choices will keep you from having a weed named after you. Your descendants will be so glad!

Daniel J. Hilburn
Administrator, Plant Division
Oregon Department of Agriculture

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