What kind of plant is this?

 What kind of plant is this?

 My daughters sprinkled some pumpkin seeds in a flower bed and we started getting this plant. It grew and grew, but no flowers or fruit. I assumed it was a pumpkin plant. 

This year I improved the soil and it came back. Again, it grew and grew, but no flowers or fruit. I noticed a pumpkin plant growing on the other side of my yard and it looks a lot different. It has tons of flowers, but the leaves are much pointier. 

What kind of plant is this?

I have taken a leaf to the local Garden Center and sent a picture to the University of Maryland Home and Garden Center for review by a master gardener. 

 But I thought maybe someone on ActiveRain might know. 

So, do you know what kind of plant this is?