Mowing roadside weeds

Those battling weeds in natural areas can't help being depressed as they drive along and see large populations of enemy plants. Late summer is especially bad as these weeds start setting seed.

Some of these weeds are biennials, and can be controlled if they are mowed at the right time. Over the last few years the mowing crews seem to have realized this and now are trying to work at the right time. Unfortunately, with the large mowers they use they can't get next to sign posts, guard rails, and other permanent structures at the edge of the highways.

Road crews are unable to mow next to guard rails and other permanent structures in the right-of-way

Kathie and I did a brief survey of the unmowed weeds present along this particular Dane County Highway KP guard rail. The diversity was not surprising. What was disturbing was the number of perennial species, since these cannot be controlled by mowing. They must be sprayed with a broad-leaf-active herbicide.

Weed along guard rail	Life style
Aspen	Perennial
Bird’s foot trefoil	Perennial
Canada thistle	Perennial
Chicory	Perennial
Common ragweed	Annual
Giant ragweed	Annual
Queen Anne’s lace	Biennial
Trifolium (short white clover)	Perennial
White sweet clover	Biennial
Wild parsnip	Biennial
Yellow sweet clover	Biennial

Some of the shorter weeds, such as bird's foot trefoil, "like" to be mowed. That is, because of their short stature the mower misses them, and since competition from the taller-growing weeds no longer occurs, they flourish. This is why bird's foot trefoil is so common on mowed median strips in urban areas. 

Despite the diligence of road crews, I am not encouraged that significant control of our roadside weeds can be developed. There are too many ecological and political problems.