I would like to send a couple of samples of my tumble weeds to a reputable lab for identification purposes. There is a variety of Russian Thistle that has beneficial health properties and one that causes epileptic seizures. I would like to know which I have. Does anyone have the name of a lab or an expert to whom I can send some samples to?
Do you know which species it is that has the beneficial properties? There are only three Salsola species that occur in AZ according to http://plants.usda.gov (S. tragus, S. paulsenii, and S. collina. Note that S. tragus also has a few synonyms S. iberica, S. australis, S. kali, S. pestiefer, S. ruthenica) If it's something you found on your property (vs something you planted on purpose) then it is highly likely it's one of those three that occur there naturally.
If one of those is beneficial, I'd start by posting some images here. I'm not sure how different the various species here, but some people here are quite good with ID's so if the species are easily differentiated you may be able to get it solved here. You might also try a local botanical garden before you spend money trying to get it identified--they should be familiar with which species are common in your area and can probably differentiate between them as well.
Thank you for taking the time to look into this. I will go back and see which of those three AZ varieties is toxic. I did not plant them here, but they are considered an invasive species - as they are not native. I can take a picture, but they are all dry and brown...perhaps the spring would be better for photos as they are green then?
If you didn't plant them then it's a pretty safe bet they're one of those three species, those are the only kinds that would show up in your area on their own. None of them are native to AZ, they're all introduced but have naturalized in the wild.
It doesn't hurt to take some pictures of them now--I don't know the genus well enough to know what features distinguish one species from another but it's possible someone might be able to narrow it down now. Then if nobody knows, you could try again in the spring.