I have a large section (30 x 30') of this stuff and want an organic way to get rid of it. I know about horticultural vinegar. How to apply? Any other solutions?
Also, can I wait until the plant dies down to do it?
If that is the plant you're talking about, I wouldn't waste time with the vinegar now. It's an annual so once those plants die back, they're dead so there's no need for vinegar. The trouble is all the seeds they will have already left behind. I'd recommend applying a pre-emergent herbicide which will prevent the seeds from coming up (the catch is it'll stop desirable seeds from coming up too, so you can only use it if you aren't starting other things from seed in that bed or hoping some of the other plants there will reseed). The pre-emergent will need to be reapplied periodically during weed sprouting season to be its most effective. You will probably still get some new plants sprouting up next year, but there'll be fewer than if you don't use pre-emergent. Make sure you pull/kill those new plants before they go to seed.
Thank you ecrane3. Yes, that is the culprit. I know the seeds are big trouble. What about corn gluten meal in early spring--would that help? What other suggestion do you have for pre-emergent herbicide? this infected area isn't near any crucial vegetation but is inhabited by wildlife of course.
Yes, corn gluten is a good organic pre-emergent. If you buy it in a package that's being sold as a pre-emergent herbicide it'll have instructions on it for how much to apply, how often to reapply, etc but if you buy it from another source you can probably find application rate & timing if you search online. Timing for application depends on when your weed seeds typically sprout--early spring sounds reasonable for your area.
If you're looking for something organic, corn gluten is the only one I'm aware of. If you don't care about organic or not, just go to your local nursery or big box store and you shouldn't have trouble finding the non-organic ones.