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Invasive weed, Whitetop, making rounds in state, county

State officials are seeing an infestation of a particularly bad noxious weed known as Hoary Cress or “Whitetop.”

Contributed photo / Oregon State University
State officials are seeing an infestation of a particularly bad noxious weed known as Hoary Cress or “Whitetop.”

A pretty ground cover of white flowers? Think again, say state noxious weed officials, as chances are way better than average you are actually seeing an infestation of a particularly bad invasive, noxious weed known as Hoary Cress, which goes by its common name of Whitetop.

“Whitetop is generally the first noxious weed that we attack in the spring. The plant has spreading roots that get into lawns, pastures, roadways, and garden areas. Because it develops very thick canopies and absorbs a lot of water and nutrients, it does a great job of choking out native vegetation,” said Roger Batt, Idaho Weed Awareness Campaign coordinator.

Hoary Cress, one of 66 noxious weeds listed in Idaho, typically grows up to two feet tall. Multiple branches grow off of the root system with white flowers at the end of each branch. The weed not only can produce by seed, but has an integrated root system that allows it to creep vertically and laterally into unwanted places. The leaves of this invasive plant are light green with a distinctive white midvein.

Idaho County producers are also being advised this is a problem to be aware of within the region.

“Depending upon which control method is used, controlling and eradicating Whitetop can be very simple or very discouraging,” according to Batt. “Mechanical control such as disking or plowing is not very effective. Most folks find that the weed simply comes back with a vengeance in a few weeks. Hand pulling small patches of this weed can be effective, but a majority of the roots need to be pulled with the plant and placed into a garbage bag. The best control method for Whitetop is to employ certain herbicides.”

Herbicide recommendations and video can be found at: under “Weed Control.”


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