I'm certainly no expert but here are some possibilities for the description (very tall, single stalk or few stalks?, large leaves, stems sometimes red, amaranth-like flower):

- redroot pigweed (Amaranthus retroflexus); to 2m tall; alternate, ovate to diamond-shaped leaves to 15 cm, long-stalked, dull green, prominently veined, scattered hairs; there are male and female flowers that differ somewhat; reddish stems
-a hybrid between redroot pigweed and green amaranth (A. hybridus); the latter is hairless, but hybrids with intermediate characteristics occur
-lamb's-quarters (Chenopodium album); to 2.5m tall, extremely variable; leaves up to 12 cm L x 8 cm W, wavy margins, alternate, green above and mealy white below; leaf shape varies - triangular, diamond-shaped, lance-shaped; stems bluish-green, blotched with red or purple

Have you seen it, or is that her description? (Just wondering because, often, when I actually see the plant I've been asked to ID, I wonder where the heck the description I heard came from, LOL!)
Does "prickly" mean with actual thorns, or with stiff hairs, or rough-surfaced? What is the leaf shape; alternate or opposite? Annual or perennial? I guess I'm assuming it "just showed up" which would suggest it's a weed, or did she actually plant it? Could you post some pictures?

That's probably it! I don't know Shirley nor have I seen the plant in person. This was the description from the local newspaper tonight, so I was just wondering what you folks thought first. My first thought was an Amaranthus too, but I wasn't sure about the species as you know there are so many of.

This plant mysteriously showed up in her yard this year, so, yes, it does suggest it is indeed a weed and most likely A. retroflexus as you say. I remember having this particular huge weed too in my garden a couple of years ago. I left it for a while figuring it was a self-seeded ÂLove-Lies-BleedingÂ, ugly looking thing, good thing I pulled it out before it reached itÂs potential size!

Much appreciated, I will contact the newspaper and let them know your likely response. If not, I know the daughter who works at the hospital with me, maybe she can get a photo ;)

Sharon