Field Guide     Weed Management     False Ragweed

False Ragweed (Parthenium hysterophorus)

Crop Impacts: hay and pastures

False Ragweed 1

About False Ragweed:

False Ragweed is a warm weather, broadleaf, annual weed that is native to southern Canada. If this weeds leaves come in contact with human skin it can cause dermatitis. It is important that you keep False Ragweed out of hay fields and pastures. If it is ingested by lactating cattle they will produce bitter milk. Due to the high amount of pollen it produces it can be a major contributor to hay-fever.

Family: Asteraceae/Compositae–Aster Family

False Ragweed 2 False Ragweed 3

False Ragweed Scouting and Prevention:

False Ragweed is a coarse weed that stands at about 12 to 40 inches high. Each individual flower head reaches about 4 to 5 mm in diameter, consisting of 5 white rays and many disk flowers. The leaves of False Ragweed are deeply lobed and about 4 to 8 inches long.

Common locations

  • - Moist soil
  • - Fertile loamy soil
  • - Pastures
  • - Hay fields

Prevention

Prevention of False Ragweed is less expensive and less time-consuming than trying to control it. Make sure when you are seeding a new area you are doing so with certified weed-free seeds. If there is an infested area on your property, be sure to drive around, instead of through it. Finally, make sure to give all equipment that has been in infested fields a good clean, to make sure no seeds are transferred.

False Ragweed Control:

Cultural Control

False Ragweed has been shown to not tolerate being mowed well. Due to this weakness of False Ragweed, keeping your lawns mowed and gardens cultivated and or hoed regularly will eventually reduce the weed. Covering the soil with organic materials will keep the soils nutrients up which will help keep ragweed from establishing.

Chemical Control

Due to the fact that False Ragweed is a broadleaf weed, the use of any broadleaf weed killers will work sufficiently. Over the past year ragweed has been showing some resistance to glyphosate which is an active ingredient in Roundup which is supposed to kill anything it comes into contact with. Trying to control older and larger plants is much more difficult and time consuming, therefore timely application is critical. Herbicides will be ineffective if applied when the plant is under stress. The herbicides will have more effect right before or right after rain due to the fact that the roots of the plants are taking in water at the time, which in turn means they will be taking in the herbicide as well. The best time to apply herbicides to False Ragweed is in mid-spring to early summer.

Latin / Alternative False Ragweed names:

  • - Franseria acanthicarpa
  • - Ambrosia acanthixarpa
  • - False Ragweed
  • - Bur ragweed
  • - Annual Burweed
  • - Ragweed Parthenium

Additional False Ragweed Resources

http://uvalde.tamu.edu/herbarium/forbs-common-name-index/ragweed-parthenium/

http://www.phadia.com/en/Products/Allergy-testing-products/ImmunoCAP-Allergen-Information/Weed-Pollens/Allergens/False-ragweed/

http://www.noble.org/apps/plantimagegallery/Plant.aspx?PlantID=70&IndexType=CommonName&PlantMainName=False%20Ragweed&PlantTypeID=1

http://www.cbif.gc.ca/eng/species-bank/canadian-poisonous-plants-information-system/all-plants-common-name/false-ragweed/?id=1370403267107