By JEFF BURBRINK
Extension Educator, Purdue Extension Elkhart County
GOSHEN — It’s been about to three years since the first Palmer Amaranth (Amaranthus palmer) was found in Elkhart County. Since that first confirmation, there are now four or five confirmed sites.
Now is the time of year to be looking for Palmer Amaranth in your fields because it stands out so well. Palmer
amaranth is a member the pigweed family. There are several closely related pigweeds that can be confused with it. Common waterhemp is the one that is most commonly confused with Palmer, and is just as troubling. We also have spiny amaranth, smooth pigweed, and redroot pigweed that can be confused with Palmer.
A key identification tip for Palmer are that some of the petiole (the stem on the leaf that Palmer is more heart shaped than waterhemp which is more elliptic (oblong). Lastly the head will be long and if female it will also be spiny.
There is no one thing to look for that is a sure sign in all cases the plant is Palmer. It can vary its looks a little from plant to plant. Here is a link to a good Purdue publication on the identification and management of Palmer Amaranth.
Another weed we are seeing in the county is Johnsongrass. While primarily limited to York and Middlebury townships, I have seen scattered patches on roadsides in Jefferson and Washington townships, too. It is listed as a prohibited and noxious weed by Indiana law.
This grass differs from other sorghum grass species in being a perennial that spreads by vigorous rootstocks. For this reason it is difficult to eradicate where not wanted and may be a troublesome weed. Stems of Johnsongrass are about quarter inch in diameter, and up to five or six feet tall. Leaves are numerous, long and slender. Growth is very vigorous, often growing in fence rows and ditches as well as crowding out crops in fields.
If you find Johnsongrass or Palmer amaranth in fields this fall, take care to not run the plants through your harvester. It is one of the best ways to sow the seed across your fields. Several people have told me they save their “Palmer fields” for last, destroying the plants by hand that escaped herbicide treatment, and running sawdust through the combine to clean the seed from the machine.
Control of Johnsongrass and many other weeds can be found in the Purdue/Ohio State/Illinois Weed Control Guide, found free on the internet.