the yield will depend on the srain you are growing. 18 gallon pot!! thats a huge pot man! On my first outdoor grow I grew two OG kush clones in 5 gallon pots with no trellis work. They grew to be 8 feet tall from the bottom of the container to the top. Each plant yielded a little more than 8 ounces. Now OG is notorious for being a small yielding plant, so I don't think you should have any problem meeting your hopes if you keep taking good care of her as you have been! Respect