HOW TO CONTROL DOG FENNEL IN PASTURES AND LAWNS
Got a call yesterday about controlling Dog fennel in a hay field and to be honest have to do some research on appropriate control measures. So rather than waste the information I thought I would add it here in case someone else has this lovely problem.
Dog fennel weed, I found has a few common names (stinkweed, Mayweed) and seems to occupy all lower 48 states. Considered an annual bushy ill-scented herb, must be where it got it’s name “stinkweed”.
Dog fennel is a short-lived summer perennial. The leaves of dog fennel are divided into thread-like segments, giving a fern like appearance. The leaves will omit a foul odor. The stems of dog fennel are reddish in color, hairy and arise from a woody base.
The flowers of dog fennel are small and white in color. The flowers are numerous and are borne on branched panicles. Dog fennel spreads by seed, and regrowth from the woody base.
Scary part that each plant of average size has the ability to produce 5000 to 17,000 seeds, thus making the plant very prolific. Once it becomes established the eradication becomes almost impossible.
Herbicide recommended for control was Trimec Classic, a selective broadleaf herbicide, as with all products we recommend you thoroughly read the label for proper application techniques.
http://www.whitman.wsu.edu/weeds/Dogfennel.html Washington State has a Great Article on this weed and some suggestion on mechanical and chemical control. They also have some great pictures for you to ID with.