I am still waiting for word from the extension agent...

Well, not only has this plant puzzled all of us, but I sent pictures to a botanist friend who forwarded to others who also sent them along and no one has identified it. Among those who have tried are the rare plant expert of Texas parks and wildlife, folks from the Steven F. Austin arboretum and the Katy Prairie Conservancy. On Monday the Fort Bend County Agricultural Extension Agent is coming out to walk the pasture in question looking for hepato-toxic plants, but I don't have high hopes.

I cannot remember another plant that has stumped everyone so much! What an intriguing mystery.

This has been fun. I wonder if we could request detailed photos of the various parts of the plant so we can keep trying to figure it out.

jvdubb said:I cannot remember another plant that has stumped everyone so much! What an intriguing mystery.

Wow, Porkpal, that is something! Will the agent take a plant to the lab for further study?

I already took him a sample but I don't know what he did with it except to send off pictures to his experts.

I do not have a very good camera, but I will gladly take more pictures if you tell me what parts you need to see.

The ag.extension agent walked the pasture where the plant grows, took pictures and samples of several other plants, but still had no idea what the original mystery plant is, nor what else could have caused the horses' liver damage.

Back to square one.

Could this be it, Sclerocarpus uniserialis?

http://www.wildflower.org/gall...

Found another pic:
http://calphotos.berkeley.edu/...

ABSOLUTELY! WOW! Sue, I believe that you have nailed it. Everybody take a look at the links, please, but I really think that this is it, and am ready to call it identified.

Thank you to all who helped solve the mystery.

Amazing!

Great! I don't see it listed as toxic anywhere that I've looked so that still leaves the problem with the horses. I expect you've ruled out kleingrass in the pasture and hay, Porkpal?

Well, it surely looks like you have a very special plant there. Congratulations to you and Sue for finding it,

I've been watching this thread, hoping this would be resolved... looks like it is!

What helped you narrow this down, sooby?

Sclerocarpus uniserialis:

This image has not been verified.

Two specimen images that have been verified ..

http://www.wildflower.org/gall...

http://www.wildflower.org/gall...

The first shows leaves which are narrower at the base, the second shows leaves with finer serrate margins.

It's difficult to say anything definite about the leaves on the calphotos site, and there is no verification.

There is a verified image of Sclerocarpus uniserialis var. uniserialis which could match and is from TX, the other photos appear to match also but are all unverified.

http://www.wildflower.org/gall...

This might be a variation of the species according to location. Could you see what the extension agent thinks?

The genus is distinguished morphologically by the pales, which are modified to completely and tightly enclose the mature cypsela (achene) and often have a tuberculate surface

https://en.wikipedia.org/wiki/...

I'm not entirely sure what the 'pales' are but the achene are the forming seeds so I guess the pales are the receptacles enclosing the forming seeds ..

https://www.google.co.uk/searc...

https://www.google.co.uk/searc...

An illustration on efloras (plant on left) which shows it could be Sclerocarpus uniserialis ..

http://www.efloras.org/object_...

The photo showing the side view and receptacle certainly bears a striking likeness to the illustration of the side view on efloras.

http://garden.org/pics/2015-11...

So far,

Chillybean said:What helped you narrow this down, sooby?

I found and went through the Texas vascular plant checklist, Asteraceae family section:
http://botany.csdl.tamu.edu/FL...

Many of the entries link to an image, where they didn't I Googled that genus for images, and some sections I could skip because it was obviously not a candidate (like thistles and some others I'm familiar with). There are three pages and needless to say I started at page 1 and found this on page 3 I figured it had to be in there somewhere and since I'm trying to rest a sore shoulder it was an interesting diversion. Not to mention there are sick horses involved....

I blew up the illustration and the side view porkpal posted to 200%, I would say this is a match!

You can also see the "pales, which are modified to completely and tightly enclose the mature cypsela" which appear to be individually enclosing the seeds.

Hurray!! Fantastic!

Great work, Sooby!