Some plant ID apps think this is a kind of lamb's-quarters but our correspondent disagrees and so do I. It was pulled from a perennial bed. Roots appear to be rhizome-like.
Well, not lamb's-quarters for sure. I feel like it is going to end up being something in the Asteraceae, but... hmm. Did you resolve it since this was posted a week ago?
Pl@ntNet identify (plantnet.org) is suggesting Dysphania ambrosioides. Dysphania ambrosioides (L.) Mosyakin & Clemants, Jerusalem-tea (World flora) - Pl@ntNet identify (plantnet.org).
I am doubtful about that -- almost all photos of the Dysphania are of a single stemmed plant from top to bottom.
I don't know it at all, but there is this one that is included among the photos on the page I linked to above: 81073e5d6a0f2a1ea1335617de3b5f657961cc1c (675×900) (plantnet.org) Other suggestions were Atriplex patula and Lepidium latifolium. It shows those both with very low probability, but the Lepidium doesn't seem too far-fetched. Here's a page on that: Bitterkrassing, Lepidium latifolium (skolvision.se)
Hello Daniel, The plant hasn't been identified. I asked the correspondent for another photo when seeds or flowers developed but I think the pulled plant was the sole specimen. Thanks.
I would also have been curious to know if they (or a close neighbour) had a bird feeder and used commercial seed products.
