Noxious Weed Profile - Ragweed spp.
Table of Contents
3. Current Status
6. Growth Habit
7. Method of Propagation
9. Other Comments
10. Related Links
English - common ragweed, giant ragweed
Figure 1. Common ragweed (A - plant beginning to flower; B - spikes of male flower heads ready to release pollen).
Figure 2. Giant ragweed
Ontario Weeds Act - noxious
Pub 505 - Pollen causes hayfever
Common ragweed is common in all parts of southern Ontario and giant ragweed is found in south western Ontario. A common weed in disturbed soils or where the overstory of tree and shrub growth has been removed.
Susceptible to 2,4-D, dicamba, glyphosate and a number other in crop herbicides. Common ragweed is listed on the label of many herbicides. Some labels also include giant ragweed. A single mowing will delay but not prevent flowering. Repeated mowing is necessary to prevent pollen release.
Giant ragweed flowers (sheds pollen) in mid July and common ragweed flowers in mid August.
For more information:
Toll Free: 1-877-424-1300