I got mine from the Butler Co. Longbeards NWTF. Our NWTF usually gets seed each year. This year, they didn't order any because they had some left from last year. Now, keep in mine I'm sure this seed is 2 years old when NWTF gets it. So, the seed was 3 yrs. old this year and had me questioning germination. But everything came up great. D&G Archery in Rochester, KY usually holds most of the seed. If not them, the owner of the New Image Oil Change place in Morgantown will have seed. They get them early spring most years. https://www.uaex.edu/publications/pdf/FSA-2150.pdf I found the above link this year after a little research. My SS Rep. is on my DU committee so we talk a lot. He suggested burning down with Roundup and Dual. Dual is a residual and roundup is a contact kill. This is pre-planting. He told me if I did that, I wouldn't have much left. Well, it was already too late to spray Dual when I talked to him. So last year, I used 6 row-30" spaced cultivators and cultivated the sunflowers like old timers used to do corn back before herbicide. Spartan is also another herbicide that can kill more than Dual. Read the labels. Dual is a grass killer. When looking at Lightning, I've read everything under the sun. My rep says to spray early, the smaller the better. I read somewhere that sunflowers need to be 4-6" tall before spraying. The label says it will work on weeds up to 4" tall, some 8" but mostly 3-6". The label also says to only spray Lightning once. So from my farming experience, you have a dilemma here. How good does lightning work after a contact kill? I'm not sure what the answer is. The label says to cultivate a week after the spray IF it's been dry. So that tells me there is some residual in it. You don't want to turn up untreated soil after spraying unless you have some residual to it. You always want to spray when as much of the weeds have germinated and came up as possible, but still want the weeds to be as little as possible. So, there's gotta be a happy medium there.