Field Guide     Weed Management     Volunteer Sunflower

Volunteer Sunflower (Helianthus annuus)

Crop Impacts: Pasture

Volunteer Sunflower 1

About Volunteer Sunflower:

If appropriate crop and herbicide rotation is not used in fields, volunteer plants will arise. A Volunteer Sunflower is left over from past crops. Sometimes they appear because not all the seeds from the previous crop were completely harvested, many of their seeds can fall on the ground during harvest or they can be spread by farm equipment. If the seeds are able to survive the winter months, it has the potential to germinate and grow in the next year’s crop. The problem with Volunteer Sunflowers is that they can compete with the desired crop in that field for that year and contaminate the harvest.

Family: Asteraceae Family

Volunteer Sunflower 2 Volunteer Sunflower 3

Volunteer Sunflower Scouting:

Detecting Volunteer Sunflowers in your crop fields is quite easy, due to its large and very prominent yellow flower, and yellow-brownish to green central disk. They typically grow up to 15 ft. tall with a thick stem. As a volunteer weed, it may not reach full height or stem thickness.

Common locations

  • - Sandy Soil
  • - Loamy Soil

Volunteer Sunflower Prevention and Control:

Prevention & Cultural Control

Make sure to give all equipment that has been used in harvest a good clean, to make sure no seeds are transferred. To eliminate any chance of planting the wrong seed, segregate seed supply by trait. There are four main steps you can do to make sure you are doing your best to control the spread of unwanted plants. 1) Go over the herbicides chemistry for burn down application before planting. 2) Integrate post-harvest cultivation into your field maintenance. 3) Use control measures that can be done in non-crop areas. 4) Plant certified seeds to reduce the chance of unwanted plants from growing. That being said, it is impossible to say that a bag is 100% pure seed because of the way seed production happens, and the potential movement of pollen. Overall, for managing unexpected volunteer plants in crop fields, you should rotate your crops, rotate the group herbicide that is used, rotate herbicide tolerant plants, rotate the time in which the herbicides need to be applied, and finally till your fields.

Chemical Control

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. Sunflowers are sensitive to atrazine, sulyphonylurea (ALS) and other carryover herbicides.

Latin / Alternative Volunteer Sunflower names:

  • - Helianthus annuus
  • - Common Sunflower
  • - Annual Sunflower

Additional Volunteer Sunflower Resources

http://www.croplife.ca/issues/herbicide-tolerant-volunteers

http://www.omafra.gov.on.ca/english/crops/pub811/7other.htm#srotation

http://www.aitc.sk.ca/saskschools/sask/sunf.html