As I recall from a pesticides course many years ago, a "weed" is any plant growing where you don't want it. If you've potted it and love it, then it's not a weed. P.S. I haven't any idea what it is.
@ponderoni, I heard those exact words back in the 60' s from a very well known radio gardener in the UK. I have no idea what it is, but can see it is being cared for, loved and enjoyed, so that is all that matters.
Well, maybe. What you have there is Common Kochia, Burningbush or Common red sage (Brassia Kochia). Depending on where you live, it can be a lovely, quite tall, airy addition to your garden. Plant several in the back about 3-4 feet apart. In some areas of the USA Burningbush is considered an invasive species. So if you decide to keep it, be sure to harvest any volunteers that pop up. This is also a useful plant. Native Americans used it for medicine and stock forage and I used it to create a lovely handmade paper. This plant was plentiful east of the Cascade Mountains in Washington and Oregon, USA. They flourished in the plentiful sunlight and saline-rich soils. So I'd do a little research to see what the normal soil pH and whatnot is for the Big Basin and pamper your Burningbush accordingly! :D Enjoy!