I think it is a weed but thought it looked similar to common milkweed. Doesn't look as sturdy as the milkweed.
Hopefully someone with more knowledge will reply.

Otherwise, I see you have spirea, heuchera and in the very front
some sedum-all good things.

Speaking from experience, get rid of the tiny little
shoots like the one growing right at the base of your questionable plant.
Those buggers will take over and they are a real pain-stick to your gardening gloves
too.

Looks like common milk weed. The seeds blow around and plant themselves everywhere. You can keep them and enjoy them till they bloom as well as a nice home for the monarch caterpillars. However you'll want to snip of the huge seed pods before they bust open to help prevent them from spreading everywhere.

I think milk weed as well. They may have been purposely planted as a food host for the monarch caterpillar although the placement is odd in front of shorter plants such as the huechera. Agree about snipping off seed pods.

Agree milk weed. Great for the butterflies!!!