Just looking threw last years pics and found a pic I had forgotten about! Its a late sprouting sunflower from bird seed! Checking the dates, it was taken on 22nd october 2015 and it was just about to open its tiny bloom! It was gone a few days later when something ate it! It was less than 1" tall and very thin stem! Yours might decide to do the same and be long dead by the time may comes.
