This is also evidence of how much it pays to know your seedlings. When this and a companion sunflower (blown over in a windstorm) as well as several tomato plants sprouted out of the compost bin's soil, I could have yanked them. But I knew fairly quickly what they were and let them grow. Now I have beauty and tomatoes. Yay!
(Please ignore the tall weeds, brick pile and rotting fascia as best you can.)