Hi, it's pokeweed, I think. The birds carry it from place to place, so it can be weedy. Some folks from Missouri told me that it makes good jelly, but it is listed as being poisonous too.

From Rutgers harmful plant gallery:

"This plant is also called inkberry because of the purple fruit. Raw fruit has been said to cause stomach aches, while cooked or baked fruits are apparently safe. The large taproot is poisonous and is capable of killing people and livestock."

http://njaes.rutgers.edu/harmfulplants/plant.asp?22

young shoots that contain no purple are supposed to be edible as well... it is common in northern california though i've never seen a 13 foot tall specimen! i've never messed with it as a wild food source, too many edible things around that don't have a poisonous stage to the senescence...
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Oh, yes it is pokeweed, also known as inkberry. Dig up the whole root otherwise it will keep growing back. You want it out before the berries turn purple and are ripe, as to not have it add all it's babies to your garden. I think there is a song about this plant, "Pokeweed Sally"?

and the song Poke Salad annie.......I too am constantly pulling this darn weed out..........