Hi Mary,

Can you send in additional photos? I am having a hard time seeing distinguishing features from this photo. When I zoom in, the leaves and flowers are out of focus.  I would need photos of the stem and leaves and a closeup of the seed head to be more confident.

If it is poison hemlock the only real hazard is eating it or inhaling it if you're mowing it and fine particles are in the air. Touching it is generally not a problem. 

Here is an article that goes into detail about how to ID poison hemlock. 

And a really great comparison guide of plants in the carrot family, including poison hemlock. If you scroll down to slide 9, you can see that poison hemlock has characteristic purple spots on the stems and the stems are smooth – no hairs. They may appear to have a waxy, whitish coating. I hope you take a close look at this guide because it's very helpful. 

I think you have a type of Torillis or hedge parsley. According to wikipedia, another common name is "tall sock-destroyer." Common names can be funny!

It's hard for me to tell the exact species from the photos , but it is most likely Torillis arvensis or Torillis japonica. In either case, it is not native, and listed as invasive in some states. As you have found out, the seeds readily stick to animals and humans. The seeds fall and come up in the spring.

When you are removing it, make sure you don't let the seeds fall! Don't put seeds in your compost. I would recommend cutting off the seed heads and putting them in a plastic bag, sealing it, and putting it in the trash. The rest of the plant can be dug up and put in compost.