This plant (2 of them) came up in my barrel of flowers. I didn't recognize it as something I'd planted but continued to let it grow until it was nearly 3ft tall. One of the photos can be zoomed in to see tiny lavender buds at the very top. I pulled them out yesterday and they had 8" taproots. I'm thinking they were from seeds not killed in the local nursery's potting soil I used, but would appreciate any ideas as I've not found anything online. Thanks.
Plant ID Help