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
French - petite herbe à poux, grande herbe à poux
Latin - Ambrosia artemisiifolia L., Ambrosia trifida L.
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
Other provinces - noxious in Quebec, Manitoba, Saskatchewan (common only)
Canadian Federal Seeds Act - giant class 2, common class 3
U.S. Federal Noxious Weed - no
U.S. Noxious State Reg - common 3 states, giant 5 states (including Illinois, Minn for both sp.)
Pub 505 - Pollen causes hayfever
NE Weeds - Pollen from ragweed is a primary cause of hay fever.
Canadian Poison Plant - not listed
Cornell Poison Plant - not listed
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.
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