I thought this was Silphium integrifolium or Rosinweed but now I'm not sure.

Please help.
Thank you.

It's Ashy Sunflower (Helianthus mollis)

http://plants.usda.gov/java/na...

You know what, looking closer, I might want to take that back. Can you tell if the disk florets or the ray florets are fertile?

The leaves on your plant look more rouned and a ittle broader Christine.

How does it compare with Silphium radula? I found plenty of photos which look different, but these sites should be correct..

http://www.sbs.utexas.edu/bio4...

http://www.utdallas.edu/~assma...

http://www.inaturalist.org/obs...

http://www.madrean.org/maba/sy...

Silphium radula is accepted ..

http://www.theplantlist.org/tp...

On the next site it's Silphium integrifolium var. radulum ..

http://w3.biosci.utexas.edu/pr...

It's not on the Plant List..

http://www.theplantlist.org/tp...

Here are a couple more pics of the flowers if it helps, I may need to get a closer look and more pics. they're growing along our road.

It's apparently not that easy to separate Silphium integrifolium and Silphium radula. The key I have says that S. integrifolium has stems that may be smooth or hairy. If the stems are hairy, the hairs are less than 1mm long. It says S. radula typically has hairy stems and the hairs are1 to 2 mm long. I can see that your plant has hairy stems. Do you think the hairs are more or less than a millimeter?

To make things more fun, Silphiums are well known for being "promiscuous", they interbreed freely with each other producing intermediate forms. Just guessing from the pictures, it looks like the hairs are more than 1mm long? If so, Janet was right with Silphium radula.

Thank you Kent! that is all very interesting! They only grow a short distance along our county road.
And, thank you and Janet for all the helpful info!!

I think I will go get some closer pics of the hair/stems and leaves for documentation to put in the database. I'll post them here also before I close this one. It's a real pretty plant the way the flowers grow along the main stalk, and the yellow is so bright, it's a cheerful sight!

thanks again!

The seed heads don't look right to me. This is Silphium radula

hmm... I see what you mean Jay.

The flower heads in my pics look more sunflowery, don't they? When I go get more pics I'll be sure and get a closer look at the seedhead too. Hopefully later today.

Silphiums are somewhat unusual in the Aster Family in that the ray florets (what most people call the petals) are fertile and the disk florets (the flower head) don't produce seeds. That's the opposite of most sunflowers, for example, where the seeds (technically fruits called achenes) are produced by the disk florets and the "petals" are sterile.

You can see in Jay's picture above that the seeds of Silphiums are produced around the outer edge of the flower head rather than in the disk.

There is some rosinweed growing outside my office, let me see if I can get some pictures of what I'm talking about.

Let's see if these pictures help make sense of my rambling:

This is a Rosinweed (Silphium integrifolium) flower head. Superficially, it looks much like a sunflower, especially at this stage of development


But, if you pull the flower head apart, you can see that each "petal" has an ovary at its base and will produce the seed


The disk florets are greatly reduced and don't have ovaries (some disk florets do produce stamens)


In sunflowers, it would be the opposite with the seed being produced by the disk florets and the "petals" being sterile.

Thank you Kent, for that tutorial! You should submit to the gardening ideas! It's very helpful info.

Well, I didn't get around to taking those pics today but will get them very soon.

I went and took some more pics of this plant. After looking at Kents' tutorial, I'm pretty sure it's not Rosinweed... it doesn't look like the petals have ovaries.

I've come back around to thinking that it is Ashy Sunflower (Helianthus mollis)

http://plants.usda.gov/java/pr...

I think Kent is right.
Go to this link and go down about the 6th row of pictures. The bract photo on the right side looks like a match for yours.

http://www.namethatplant.net/g...

I agree with Helianthus mollis, what a tricky lot!

Downy Sunflower is an attractive plant, whether in or out of bloom. It can be readily distinguished from other sunflowers by the fine soft hairs that heavily cover both the leaves and stems; the broad clasping leaves; and the greater number of ray florets in the compound flowers.

http://www.illinoiswildflowers...

I can see the downy hairs on the closeup of the leaf too.

Awesome job, that's a match!!

Thanks everyone! Closing this one!