Just making a guess here...Wedelia texana

Ooh, that's pretty! However it is described as having narrow leaves and the blooms have too many petals.

Thanks, Greene. Actually I was replying to the previous post above, but the same comment suits your suggestion too. I promise I'll get better pictures.

I do not have a good camera,but here are some slightly more useful photos, I hope.

A branch -typical growth form


The bloom from right to left: bud, fully open, back, spent bloom


Leaf, front and back


Posed with Great Dane for scale.

Look at Geum (Avens)

I ran across this site. It might be useful to you,if not for this plant,perhaps for future reference.

http://essmextension.tamu.edu/...

Oh, yes those pictures should be helpful... I hope.

I'm still boggled though, I'm sure in those first pictures I see open disk florets.

The leaves look very similar to Geum urbanum, what I'm finding online tend to vary. The flowers are quite small, I have it growing in a shady moist place. I can't find any Geum for TX which quite matches but some are crosses.

http://2.bp.blogspot.com/-qLRY...

So far I think Geum aleppicum avens is the closest. The distribution maps do not show it in Texas and I have not yet found an image that is a perfect match in my opinion.

I have always wondered what this plant is since we bought this property over 20 years ago, but it has recently become more critical as it is the only unidentified plant growing plentifully in a pasture in which the horses have been diagnosed with liver damage. I really want to know whether it could be the cause. Thank you all for your efforts!

Janet, my plant never shows the three-part leaves of that Geum, but it does have a confusing habit of producing leaves that look as if they are opposite but end up alternate. The blooms branch off from the base of a leaf.

I found a Black Botch disease which is a mould on white clover, Cymodethea trifolii which damages the liver. Use find on this page feature.

http://agreenhorse.blogspot.co...

The horses had liver dysfunction leading to photosensitization and the clover pasture infested with Cymodothea trifolii was
considered a likely cause.

http://alfalfa.ucdavis.edu/+sy...

Thanks, Janet. Neither plant is growing in this pasture. My lovely yellow weed, in fact, is the only plant we (or the extension service) can't identify. I have removed it but I still would like to know...

The seed heads forming that I can see, and the general form of the plant do match Geum but I haven't been able to find one close. It's in the family Rosaceae but I don't know of another plant which looks like it.

These maps might help .. click show all.

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

Right, none of the species native to Texas look like my plant. I suppose it could have been introduced; I have never seen it anywhere except on my property. Could it be a cross of two different species of Geum?

There's several crosses listed so it could have crossed with a cultivated Geum, the flowers look to be quite large for a species.

My botanist friend has identified it as Viguiera dentata. It looks right to me. What do you all think?

Some how I missed Frostweed's post (reply number 20 here). She gave you the correct ID.

"How about Sunflower Goldeneye, Viguiera dentata"

http://www.wildflower.org/plan...

The leaves of Viguiera dentata don't match at all, the margins are entire.

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

this one looks very similar

http://chalk.richmond.edu/flor...

It seems to be a matter of finding the right image. The last one you linked, Jean, looks exactly like my plant. The ones I saw on the Ladybird Johnson site did not match well.