They usually will be outcompeted with time but i would spend the time pulling. The less seed put into the seed bank the better.
If you find anything that works, please let me know. Have about a 2 acre patch to deal with. Mowing impossible due to unexploded ordnance and it is a complete monoculture of 3' high ironweed each year. Cannot use soil sterilants either. Any suggestions??

I am interested in knowing why you don't like or want this plant. I have a baby meadow(just starting out and ironweed is one of the plants I wintersowed this year. I believe it is native here. It's still in the pot and I haven't planted it yet. Should I keep it out for some reason?

Ironweeds (Vernonia spp., over 100 kinds worldwide) are a component of native grassland/prairie/meadow, not only in North America, but in South America and Africa, too! In other words, they definitely belong in a meadow. As the other species get established in your planting, the ironweeds will just become an attractive part of the mix, and a good source of nectar for butterflies at a time of year when little else in their color range is available.

Funny how even we native plant enthusiasts get subliminally and unknowingly influenced by the ranchers and weed scientist types, who dislike ironweeds because they are impalatable to livestock and hard to control, respectively. Their impalatability is one of the reasons they are successful components of native grasslands, which have all developed under the influence of grazing animals.

Thanks, Doctorant and everyone else, you've saved me a lot of work from my trying to kill it. I'll just leave it alone and mow it along with the rest of what's newly germinated grass/forbs this first year. I've always liked it, but was afraid it'd be a problem with the other wildflowers. Joe D. Bryant

Ok I gotta ask....Ironweed here is a state listed noxious weed known as Kochia scoparia. Chenopodium (goosefoot) family. Sorry for presuming that was the one we were talking about. So much for common names!!

i think u mean common ironweed Vernonia fasciculata.

u definately dont wanna distroy these. prob a little wet in this area?

doctorant got it right on the head.

froggy

Here is a link that might be useful: common ironweed

Please note, the "good" ironweed, genus Vernonia (many species), has fluffy purple flowers, somewhat like thistle but with darker, more intense color and a much "softer" appearance.

Kochia (usually called fireweed) has non-showy green flowers.

Not only is Kochia (an exotic annual weed) not the native ironweed, it is also not the native 'fireweed', Epilobium angustifolium.

Here is a link that might be useful: fireweed

Very true john, and the problem with common names is what, again.....?? (my fault for ass-u-me-ing here.)
;-)

Cool,
I have the good one.

Doctorant said it best! May I add that before you destroy any native plantings maybe it would be good to see if anyone else would love to have them. I know many in Zone 5 Indiana who would be very anxious to take them off your hands if you want to kill them. That includes me. It is so vibrant and really attracts the butterflies like crazy. If in a very moist and fertile enviorment you can get them to reach 8 feet tall. Their root system really gets thick and the plant does a great job of "grounding itself in". It really holds up the large flower heads it produces. The stems are so strong that you can cut them down in the fall and use them to stake up some of your other tall growers that need staking. Enjoy them for all the benefits they have to offer to our Indiana meadows.

How could you spray something as precious as this? ;o)

If the ironweeds are overwhelming some of the other plants by growing too tall or too vigorously, you could cut them down a few times in the early summer, then allow them to bloom by not cutting later in the summer. The result would be shorter, sturdier plants with perhaps even more flowers than uncut plants. At this time of the year, cutting would probably mean no flowers this year. Once all of the plants necome established, the ironweed will be a well behaved member of the meadow. They seem to dominate meadows only where there is grazing. Lots of wet pastures around here have abundant Ironweed. It looks great this time of the year.