America is being overrun with weeds — most of them exceptionally difficult to eradicate. Some are worse than others and the worst of the bunch, the noxious weeds, pose a threat to people, wildlife or the native plants which support our ecosystem. What does this mean to the home gardener or land owner? Help out!
Weeds are dominators. Allowing them to flourish and seed means more seeds to travel and infest other areas, so we all need to help in keeping the population of the really obnoxious weeds down. Here's a primer on some noxious plants.
It's estimated 50 to 85 percent of us are allergic to poison oak (Rhus diversiloba or Toxicodendron diversilobum), and those who are, may consider it the most noxious of weeds.
Digging it up by hand is one method of eradicating it, but only by the non-allergic. Leaving even a half-inch of root in the soil will allow it to re-grow.
Once the plant is up and the leaves are full-grown you can spray it with CrossbowTM. But be sure there is no breeze, and the temperature is well under 85 degrees. Over 85 and it vaporizes and carries for miles. Grapes are particularly sensitive to it. Jerry May of the Grange Co-op says to always use a wetting agent with this chemical.
Another way to kill it is to cut all branches back to the dirt in spring and then immediately put an herbicide in the stump. This might have to be repeated. Never burn this plant. Dispose of it in the landfill or bury it deeply.
You can try smothering the plant by cutting it back to the ground, then covering the stump with a board, tarp, carpet, or many thick layers of newspaper. Remember that the root will stay toxic for years.
First, "there is no quick, cheap or easy way," says Tim Andrade of the Grange Co-op's agronomy division. "You can minimize them but they'll always be present, and it typically takes at least four or five years [of work]."
There are three ways to get rid of these weeds: mechanical removal, including hand pulling, biological controls, and chemical controls. While spraying with chemicals can help, the timing of the spraying is crucial. Different chemical sprays should be used at different times in the life cycle, and none will work if used incorrectly, according to Jerry May, agronomy operations manager at Grange Co-op. Experts can help you determine the type of herbicide, but it is crucial to follow directions exactly.
Mechanical controls will work for some species and not others. Biological controls (mainly insects or diseases) do exist for some weeds and goats actually are among the best weed control "systems."
"The worst [weeds] are bindweed and star thistle," says May. "You leave a 1/2-inch root of bindweed and it will grow right back. One star thistle is too many — because the seeds will live in the ground for 7 to10 years. And puncture vine spreads everywhere because the seed needs less than 1/8-inch of soil to grow."
"One mistake people make is waiting too long to tackle the weeds," says Laird Funk of Omnitech Environmental Solutions in Williams. "You need to hand-pull star thistles before they flower and set seeds, and you have to cart them away, because if you pull it and let it drop, it will sometimes go ahead and ripen seeds while laying there on the ground."
The plants listed here are spreading through Southern Oregon. It is thought that cultivars of butterfly bush and bindweed (morning glory) do not spread as the originals of the species do. Particularly dangerous weeds are accompanied by photographs.
Leafy spurge (Euphorbia esula) — milky latex can cause blindness
Medusahead rye (Taeniatherum caput-medusae) — injures grazing animals and makes land useless for other plants
Musk thistle (Carduus nutans) — spines can injure wildlife/animals
Poison hemlock (Conium maculatum) — highly poisonous to people and animals
Puncture vine (Tribulus terrestris)
Tansy ragwort (Senecio jacobaea) — causes irreversible liver damage to horses and cattle
Yellow starthistle (Centaurea solstitialis) — toxic to horses
The Federal Bureau of Land Management has a booklet to help identify Oregon's noxious weeds. For more pictures and information visit Oregon's Agriculture Department web site: oregon.gov/ODA/PLANT/WEEDS/statelist2.shtml