Hello,

You may have water hemlock, and I am glad you are being cautious. I am sending you some links from University sources that have reliable information.  One is a video that shows the speaker using disposable gloves when handling the plant. 

Water hemlock has a thick  multiple branching root. If you would pull up one,or two single plants, wearing waterproof gloves, and attach a picture of the roots to this question, that will help confirm the ID. On that same picture please flatten out a single leaf branch so I can see a single branch with all its leaflets clearly. 

Control: Keep all pets out of the area while working. Wearing long sleeves, long pants, closed shoes and water-proof gloves dig/ pull up the plants, roots and all, double bag them and seal the bags. Water hemlock comes up easily when soil is moist, so water the area first if it is dry. Let the bags sit in full sun for a week so that the plants are killed, then throw the bags away, still sealed.  If you can't get these dug up now, and  plants are already forming seed, clip the seed heads off and all the flowers, too, and bag them. This plant spreads by seed. You don't want any more seed falling to the ground than necessary. Continue to monitor your area and the neighbor's yard for more plants. Seed from wildlife or soil brought into,the yard are possibly how this got its start. When done working wash your clothing separately from other laundry.

This plant likes moisture so, allowing the soil to dry (after you have dug all visible plants out) should help control it. Chemicals listed as effective controls are glyphosate and 2,4-D. If it is near water then use only waterway safe products. Always follow all label cautions and instructions. Repeat applications may be necessary. Note that dead plants are still toxic.

Here is the video showing how to identify it and the root:

https://m.youtube.com/watch?v=Q-TCce8tJlM

Here are articles discussing ID and control:

https://www.extension.umn.edu/agriculture/horse/pasture/poison-hemlock-and-waterhemlock/

https://extension.umd.edu/learn/toxic-plant-profile-hemlock

I may have you send a sample to the MSU PESTID Lab if your root picture doesn't confirm the ID. There are many non-toxic relatives that look similar. I hope to hear from you soon.

Hello,

I'm glad you sent more pictures, that helps. I think you have the all green version of goutweed, Aegopodium podagraria 

If you search the internet using the scientific name, above, you will see pictures of it. 

The picture of roots you sent do not match up with water hemlock, and neither does the individual leafy branch. But they do match goutweed. If you want confirmation you may still send fresh samples, including the root, along with your pictures to the pestid lab. The submission form, instructions, and fee schedule are here--- www.pestid.msu.edu

Some people do have a skin reaction to this family of plants so, cover your skin when working with goutweed.  Here are details on this aggressive plant:

http://hyg.ipm.illinois.edu/article.php?id=899

I'm glad it isn't water hemlock!