Glenn Nice, Weed Diagnostician, Botany & Plant Pathology Department, Purdue University
The term ‘Goldenrod’ is quite common. It is a common name attached to several plants. In Indiana we have several - white, gray, and showy goldenrod. We also have some named after places and people such as Buckley’s, Missouri, Deam’s, Mount Albert, and Canada. Some are descriptive, like wreath, giant, downy, roundleaf, wrinkleleaf, or elmleaf. There are some named for time of the year, early or autumn. There is even one named zigzag goldenrod. In fact the name goldenrod is connected to eight different genera. It is the genus Solidago that most of the goldenrods belong to.
In Indiana we predominantly see Canada, Missouri, and Giant goldenrod. The table below breaks down the three major species found in Indiana. Goldenrod can be found in ditches, roadsides, and meadows. This year we saw them along many fence rows. As the name suggests, in most cases, goldenrods have yellow flowers and are often recognized by the yellow inflorescence that reminds me of a yellow fireworks display (see photo).
Goldenrods are native to North America. Although they are often blamed for flaring peoples' allergies, they are most likely taking the blame for giant ragweed, which also blooms around the same time. I have not heard of goldenrod causing a problem in corn or soybean, even though it might watch from the margins of a field. However, goldenrod can sometimes interfere in a pasture. There are no toxicity issues that I am aware of, but I can’t vouch for the palatability.
In a grass pasture both dicamba (Banvel, Clarity, Sterling, others) and glyphosate (as a spot treatment) are effective on goldenrod. Dicamba at 1 lb active ingredient can be applied broadcast to control surface plants; however, to control rhizomes, spot treatments can be done with dicamba at rates up to 2 lb active ingredient. The use of 2,4-D is not as effective as dicamba, but still is good at higher rates also. Crossbow also has activity on goldenrod at 4 qt/A or at a 1.5% mix. To get control of the rhizomes, retreating may be required with Crossbow.