[clicka15]

Hello Aeshna5,

I'm not convinced it's Fat Hen (Chenopodium album) because it is much more upright in character than my plant above, and the leaves of Fat Hen are more serrated.

It was one of the species I checked before posting the photographs, but unless it is variable enough to grow in a more rambling fashion, I reckon it is something related but different - possibly Nettle-leaved Goosefoot (Chenopodium murale), but the flowers are redish in this species and mine aren't.

Thanks and best wishes,
Steven.