Mine is bindweed. It comes up again from the roots so you have to keep hoeing it down.

It is almost impossible to get rid of.

Here is a link that might be useful: bindweed

I don't think I have ever seen Goutweed. But here is a link to it.

Here is a link that might be useful: Goutweed

It's a tie between spotted spurge and oxalis. The more I pull, the more it comes back. I'm losing my will to pull :(

Yellow Starthistle and Russian Starthistle, both are very hard to control and to eradicate, can produce thorn heads that flaten garden tractor tires and very poisonous to Horses.

Dan

Last year, it was rattlesnake weed. Ealier this year, it was oxalis. Now, its chamber bitter.