Is this 12+ foot plant a sunflower or hogweed?
The plant in your photo is a sunflower (Helianthus annuus).  The large, heart shaped leaves and stiff, hairy stem are very characteristic of the sunflower as seen in your plant. These form a single flower head on top when mature - about 90 days after planting.  They typically grow to 10 feet in height, so 12 feet would not be unusual.  The tallest recorded specimen was apparently 30 feet in height. Please see links below for more information.

https://en.wikipedia.org/wiki/Helianthus_annuus#Cultivation_and_uses

https://homeguides.sfgate.com/time-year-sunflowers-bloom-67915.html

http://www.illinoiswildflowers.info/prairie/plantx/an_sunflowerx.htm