This weed arrived at my garden via mulch, I believe, approximately two years ago and is now well established in my gardens. Roundup does not kill it. I have been painstakingly digging it out. It has hardy underground roots that send up new plants from bud every few inches. Is there a chemical that will kill this? This is a growing and frustrating problem. I believe if left unchecked it will be the only thing growing. Help.
This is goutweed, also known as Bishop's weed, a foreign invasive plant that was originally introduced as a groundcover. It's a bear to get rid of. Here's help (scroll down to Weed of the Week): https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/ipmnet/15Jun05L.pdf