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Manage noxious weeds like toadflax this fall

By Staff | Oct 4, 2019

Yellow toadflax growing in lawn. This plant is approximately 3 inches tall.

Since being added to the state’s noxious weed list several years ago, toadflax infestations are becoming more numerous in North Dakota counties, including Pierce County. There are two species of toadflax (Yellow toadflax and Dalmatian toadflax) considered invasive in North Dakota and both are on the state’s locally noxious weed list.

Noxious weed control is everyone’s responsibility and their control is to everyone’s benefit. It is the duty of each person who owns or controls land in North Dakota to effectively control noxious weeds on such land. County weed boards are the local entity responsible for administration of noxious weed control at the county level. Currently, there are weed boards in all of North Dakota’s 53 counties, and in seven cities (Bismarck, Devils Lake, Dickinson, Fargo, Grand Forks, Wahpeton and Mandan). To learn more about specific noxious weed control regulations, check out “North Dakota’s Noxious Weed Law and Regulations” publication at “http://ndweeds.homestead.com/15_NoxiousWeeds_web.pdf”>ndweeds.homestead.com/15_NoxiousWeeds_web.pdf .

Yellow toadflax and Dalmatian toadflax are members of the figwort family, which is more commonly known as the snapdragon family. Like most noxious weeds, these two species of toadflax, were introduced to North America as ornamental plants that eventually escaped cultivation. If you are gardener or homeowner, be sure to check any packages of wild flower or old-fashioned flower seed mixes for Linaria vulgaris in the plant mix, as this is the scientific name for Yellow toadflax. I say this because I have seen it listed on various flower seed packages.

Landowners should also be on the lookout for this noxious weed and waste no time in their efforts to control and contain this invasive noxious weed as it can spread up to 10 feet per year. The toadflax species are aggressive and will displace forage in pasture and rangelands. Yellow toadflax can be mildly poisonous to livestock that graze it. Although the toadflaxes may be slow to establish, once plants take root, control is very difficult since most herbicides are ineffective. Both species also have an extensive rhizomatous root system that spreads like leafy spurge.

Yellow and Dalmatian toadflax have distinct snapdragon-like flowers that are yellow with bearded orange throats. Yellow toadflax flowers are about one inch long and can vary from yellow to pale cream in color. Dalmatian toadflax flowers are about .75 to 1.5 inches long and tend to be a brighter yellow. Both species flowers appear as dense terminal elongated clusters. Dalmatian toadflax blooms in June and on into the fall, while yellow toadflax blooms later in August and September. The most distinctive difference between the species is that Dalmatian toadflax has broad heart-shaped leaves that clasp a woody stem, whereas yellow toadflax has narrow linear leaves with a narrow stem. To identify the toadflaxes and other noxious weeds, see the picture above in a lawn and check out the following publication “A Guide to North Dakota Noxious and Troublesome Weeds” at www.ag.ndsu.edu/pubs/plantsci/weeds/w1691.pdf .

Chemical control of toadflaxes can be achieved, but as mentioned previously, there are a limited number of effective herbicides available and often requires repeated treatments at high rates. Repeated applications are necessary because yellow toadflax has the ability to recover from single treatment applications due to extensive energy reserves stored in its roots. Additionally, one must follow label restrictions, as some herbicides are not labeled for use in municipal or other areas.

It is important to note that hand pulling and mowing are not effective control methods for yellow toadflax, but can help limit seed production.

Biological control in the form of stem-boring weevils is available for controlling Dalmatian toadflax. However, these weevils have been unsuccessful in yellow toadflax stands due to the much narrower stem of yellow toadflax interfering with survival of the weevil larvae.

For more information on controlling yellow toadflax in a lawn or agriculture land, call the Pierce County Weed Board at 776-5225 or the NDSU Extension Pierce County office at 776-6234 ext. 5.

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