Hi Kathy, I have what appears to be that same 'weed' on my acres, pretty sure that it is amaranth, so rejoice! It is closely related to quinoa and lambs quarters, I have personally eaten the leaves, seed heads, and seeds, and enjoyed them, later into the season the leaves get a little strong and quite salty. I would suggest that if you are going to ingest, try a little bit first, see how it sits with you.
Pretty sure that's Amaranthus ganceticus, or a similar species, or even a hybrid--an Amaranth for sure, though. That's one of the species that's commonly grown as a garden vegetable due to it's large size and late blooming habit. Steam the young leaves and tops, cook the older leaves longer (in soup, for instance).