Noxious Weed Season - Hoary Cress (Whitetop) Control

If you have what seems to be an outgrowth of pretty white flowers that appear to be attractive ground cover vegetation growing on your property, you might want to think again.

State noxious weed officials say chances are way better than average that what you are actually seeing is an infestation of a particularly bad invasive, noxious weed known as Hoary Cress, which goes by its common name of Whitetop.

  “Whitetop is one of the first noxious weeds 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 Idaho’s listed noxious weeds, typically grows up to 2 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.

“Depending upon which control method is used, controlling and eradicating Whitetop can be very simple or very discouraging.  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.  These herbicide recommendations can now be found on our website at  It is important to note than when using an herbicide, always follow the label and safety instructions on that herbicide label,” Batt added.

Noxious weeds have already infested 8 million acres of Idaho’s lands and pose a serious threat to Idaho’s economy, ecology and agriculture.  State and private landowners annually spend upwards of $25 million to combat noxious weeds.  But even with that level of effort, thousands of acres of land are taken over every day by one or more noxious weeds known to have infested the state.

To learn how best to identify Idaho’s noxious weeds plus details about the best strategies to get rid of them, go to the Idaho Weed Awareness Campaign’s website at: or follow us on Facebook @IdahoWeedAwareness.  Idahoans can also contact their County Weed Control Superintendent or a Private Applicator for technical assistance in dealing with the control and management of Whitetop and other noxious weeds.

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