3 ft tall plant in Ontario growing from planter

I have this 3 ft tall plant growing from a vegetable planter in southern Ontario. Leaves are larger than my hand. Main stalk thickness is larger than my thumb.

It is growing in a vegetable planter that has received a lot of kitchen compost, so I have random plants like peppers and tomatoes growing alongside.

Is this a local weed or is it a fruit / vegetable plant from seeds in my compost?

 

Annual sunflower

 

Thanks, Ron!