The sunflowers have been discussed in the native plants forum. It was established that the first one has smooth stems, which would rule out Helianthus tuberosus.

I thought the sunflowers themselves, put out a toxin to prevent other plants around them. This toxin would also be in the seeds. I buy the cheaper striped sunflowers, and the hulls thrown about do make a bare area in spring grass growth. Seeds might also be treated with something, but I had not heard of it. Perhaps you could call a company name on the seed bag. I feed a lot of sunflowers during winter,usually a couple hundred pounds. With the raise in prices (doubled here, now $20 for 50#) I can't afford hulled or even the black oilers. My local birds like the sunflowers and suet I put out. We do have fields with unmowed weeds for birds liking seeds like thistle. With my quantity of seeds used, they make a large pile of hulls. I rake up my hulls come spring, use them in places I don't want growth of weeds or grass.

I have a Sante Fe Helianthus that I need to move and I'm not sure how to do it. Can anyone give me some advice? When would be the best time to move it? I've read other places that the roots are really more like rhizomes, is that correct? I love it but I had no idea it would take over like it has, in only 2 years.

acadia, thanks for the tip....I'll be doing the same....one of my plots out front has beautiful Cleome that come up every spring, so they'll be happy to have some company next year! I'm new to sunflowers....thus my questions. thank you again everyone...I appreciate it!