By Bill Kleiman, Nachusa Grasslands, TNC
In Nebraska, Chris Helzer of TNC, does no or little work against sweet clover. Perhaps Nebraska is dry enough that yellow and white sweet clover (Melilotus officinalis and M alba) are there but not overwhelming. In rain soaked Illinois we find prairie plantings can look like we are raising sweetclover hay.
We sometimes spot spray sweetclover with a pack. In ruderal areas we sometimes use a tractor sprayer.
We like weed spading sweet clover as the spade is light weight, simple, and effective. We loosen the soil next to the clover and pluck it out, rather than tug until our backs hurt. I have written about these weed spades previously on this blog.
You can see we can grow some huge sweet clover plants.
Sweet clover is a biennial so if you mow it very short, on year two, when it is in full flower the plants typically do not re-sprout. On some rocky soils it is hard to mow the yellow clover short enough to not have it re-sprout.
We use rotary mowers. The batwing mower tends to mow short enough to pick up and cut the plants knocked down by the tractor tires.
The advantage of a sickle mower is that the cutter is off to the side. Below, Austin Webb of Byron Forest Preserve is showing me their mower used for sweetclover patches. They are relatively simple, quiet as the tractor can be run at low throttle, and they are nimble to maneuver. After two seasons with this mower they are pleased.
Below, the flail mower is another way to mow weeds and lanes. This photo is from a manufacturer’s website. Flail mowers rotate the blade not horizontal to the ground but in the other dimension, like a brush mower head rotates, or a roto-tiller spins.
Below is a photo submitted by Joe Blastick of South Dakota TNC. They call this one Mowasaurus. This is a silage chopper. It is designed to cut a crop like hay with its flail mower components, then auger to its built in chopper, and then its blower sends the product into a wagon trailing behind. Here they use it to mow a fire break and then blow the product into the wind off the fire break.
I tried one of these in our Illinois 5 foot high prairie and it kept jamming the chopper with all that prairie. You want the wind to be modest or away from you. It does not like lots of rocks.
grassland restoration network 
For hand crews… What about loppers?
Loppers should work. I have used my pocket knife.
The sickle mower is also a great choice for mowing young plantings in the first year or a few as they establish. It lays down the cut vegetation evenly, and when it dries up, it doesn’t smother what’s below. Other mower types can leave smother clumps of cut vegetation.
We use a Toolcat tractor with a front-mounted rotary mower—it does a nice job on sweetclover. It’s an option to consider if you’re looking at the whole tractor/mower package. Also takes a grapple for moving brush, logs, etc. and can take a water pump and tank in the bed in back. Very maneuverable with 4-wheel steering.
We had a bad outbreak in a sand prairie restoration and hayed the field during the peak of sweet clover bloom for 4-5 years. It was a little hard on the prairie forbs, but virtually eliminated the sweet clover from the restoration. Now the site is recovering from the haying and there is almost no sweet clover. It might have been a good idea to do a forb overseed after the final haying.
I also saw dramatic reduction in white sweet clover with a hay mowing at peak flower.