Summer crews spot dyer’s woad, weed capable of damaging rangeland

2011-09-12T00:00:00Z Summer crews spot dyer’s woad, weed capable of damaging rangelandBy TERRI ADAMS The Prairie Star The Prairie Star
September 12, 2011 12:00 am  • 

It’s a summer job that doesn’t carry a lot of perks. Sure, the workers get new clothes and footwear and spend a lot of time in the sun; but their clothing consists of white coveralls and knee boots and their tans are usually limited to portions of the face.

A lot of the workers are college students coming home for the summer. They want to be able to earn enough money to return to college in the fall. They come in, work a few months and leave and all that is fine with Bob Parsons. He is the weed and pest supervisor for Park County, Wyo.

Every summer the Park County Weed and Pest staff train several crews of temporary employees to identify plants and weeds, and work with pesticides. The workers have to be strong and capable of working long, hard hours. Then they go out along the roadways, trails, and backcountry to spray for noxious weeds and other invasive plants.

This year those summer crews spotted something unusual. They spotted one single plant of dyer’s woad.

Now that may not sound like much, but dyer’s woad is considered a noxious weed that can spread at an alarming rate of 14 percent per year. And, according to Sandra Frost, University of Wyoming Cooperative Extension Service educator in Park County, a study on Pacific Northwest rangeland showed the weed decreases cattle grazing capacity on average 38 percent.

So, when one single plant shows up, everyone who knows weeds takes notice.

“The staff was out there traveling surveying along the road between Cody, Wyoming and Yellowstone National Park and they looked out and saw this one plant. It’s amazing they even saw it because it wasn’t on the edge of the road where they were working. It was 50 feet off the road, along the riverbank. It was just out there all by itself and they didn’t think it looked like it belonged there,” said Parsons.

They were right. So the crew reported the unusual plant to their supervisors who came out and took a look.

“We knew right away what it was. There was no doubt in our minds,” recalled Parsons.

At that point they brought in additional crews and spent 40 hours looking up and down the riverbank, on both sides, and around surrounding guest lodges and nearby drainages for more plants. The entire Northfork road system was searched for this plant as well.

“We went two to three miles upriver and downriver but did not see another one,” he said. Lucikly the plant had not yet gone to seed, so they dug it up, making sure they got out the entire taproot, which can be up to 5 feet long, and brought the plant back to their office. There the plant was used to train all the crews on how to identify the dyer’s woad weed.

When the plant finally did start to go to seed, they bagged it up and incinerated it, which is the best way to get rid of it.

Dyer’s woad is listed as a category 2 noxious weed in Montana and as a noxious weed in Wyoming. It is also a noxious weed in Idaho. It has a two-year cycle and can grow between 1 to 4 feet during that time. A member of the mustard family, dyer’s woad has a thick taproot. Plants will regenerate if top growth is removed or the taproot is disced.  It is well-adapted to alkaline soils and arid climates. In the spring, the plant grows rosettes of leaves near the soil and then sends up long stems. Long, lance shape leaves can reach 7 inches in length. The leaves are blue-green in color with a white or cream-colored midrib that extends for the entire length of the leaf. The plant overwinters and, the next spring, it sends out more stems and flowers but, this time, it also produces seed pods. The plant sheds its seeds in mid to late summer and dies.

According to Frost, those seed pods were once used to create an indigo-colored dye prized by weavers and spinners. In fact, woad means blue. Dyer’s woad was named in reference to the blue it produced for dyers.

Another interesting characteristic of the plant is the long, flattened seed pods that dangle from beneath the umbrella-shaped yellow flower heads. These seed pods turn from green to black when mature.

Montana established the Montana Dyer’s Woad Cooperative Project in 1984, aimed at eradicating the weed from the state. At that time, 13 counties were infested with the plant. Intensive work has reduced the number of infested counties from 13 to four and the number of acres from 480 to 6.4, said Frost.

In an effort to make sure the plant does not spread, Parsons and Frost are asking rural residents to be on the look out for any Dyer’s woad.

Producers or residents who do spot any plant that seems out of place for the area are encourage to contact their local county weed coordinator or extension office.

“Our plan is to continue to monitor that area,” said Parsons. “We will go back this fall and survey again then we will continue to monitor the area several times a year to make sure there are not any new infestations.”

“We are glad our staff were paying close attention and spotted this plant when they did,” said Parsons. “That speaks highly of our full time employees and also of the training our staff does with the summer crews before they send them out.

“Our people are trained to watch for plants that look like they don’t belong, so even while traveling down the road at highway speeds, problem weeds just seem to jump out at you,” said Parsons.  “I’m very pleased with the staff we currently have, they are truly dedicated professionals.”

So the next time you see those summer crews, remember they are doing a lot more than just walking and spraying.

They are also watching and reporting. Spraying weeds in the summer is no longer just about treating a few selected species.

It is about identifying treating the weeds that are present but also identifying plants that have never existed in an area before and getting them treated before they devastate entire areas.

Find more information on “Ecology and management of dyer’s woad”, see

Copyright 2015 The Prairie Star. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

(1) Comments

  1. Randy Westbrooks
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    Randy Westbrooks - October 31, 2011 9:32 pm

    This is a great example of early detection and rapid response to new invasive plants in action............. Congratulations to Bob Parsons and his staff in Park County.

    Dr. Randy G. Westbrooks - Invasive Species Prevention Specialist, U.S. Geological Survey, Whiteville, NC, USA.
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