By Bill Kleiman, Director Nachusa Grasslands, TNC

The recent GRN workshop was all tour based, with 5 themed tours that ran concurrently every two hours over two days. All participants could go on all 5 tours. I led the tour with the theme of weeds. We covered a lot of ground in footsteps and concepts.

Birdsfoot trefoil: We stopped at a unit with a 40 year history of invasive birdsfoot trefoil, Lotus corniculatus. The trefoil was planted for pasture forage and then later the pasture became part of Nachusa. We have experienced the long duration of the seed bank of these legumes as they continue to emerge. We have reduced their occurrence with about 15 years of careful backpack spraying and the field looks good at this time of year with only a few trefoil plants encountered as we hiked around.

The last two seasons we have tried boom spraying a pre-emergent herbicide, Esplanade 200, on the prairie planting in early spring. This kills all seeds emerging, good and bad, but it gives our weed crew a chance to catch up with the adult trefoil plants. This shows signs of success as the field looks better than ever, but we will report out later.

Reed canary grass: We looked at a wet meadow that once was thick with reed canary grass, Phalaris arundinacea, and is now much reduced in reed canary grass and dominated by native plants. We used grass herbicides intensively for several years from about 1993 to 1998 and then were able to spray with just backpacks with occasional tractor spot spraying since.

Sweet clover: We found that mowing about the 4th of July proved very effective on white sweet clover, with yellow sweet clover mowed a week or two before the white. Here is a recent post on that: https://grasslandrestorationnetwork.org/2024/07/11/yellow-and-white-sweet-clover/ On the GRN blogsite there is a search bar. There are four articles on sweet clover on the site.

Lespedeza daurica and L. cuneata: These invasive legumes take a lot of work to control. We talked about the need for careful sweeping, this refers to walking back and forth across a planting. We also agreed that at least two visits per year are needed, and three would be best to get towards success. Here are a few posts on that:

https://grasslandrestorationnetwork.org/2023/09/14/lespedeza-friend-and-foe/ https://grasslandrestorationnetwork.org/2021/09/30/needle-in-a-haystack/ https://grasslandrestorationnetwork.org/2021/09/09/beware-what-seed-you-buy/

Exotic vs Invasive: I listed some species of exotic plants that I don’t think are invasive in our area: Queen Anne’s lace, dames rocket, canada thistle, garlic mustard (as frequent fire controls mustard). I also spoke of holding back on planting the native shrub Amorpha bush, Amorpha fruticosa, as I have seen it get very dense in a new planting. Gray dogwood has been controlled with one or two mowings.

I promised a crib sheet that lists some herbicides we use and that is here: https://www.nachusagrasslands.org/uploads/5/8/4/6/58466593/which_herbicide_to_use_for_various_weeds_%E2%80%93_2023.pdf