I am trying to grow Helianthus in my garden!  Have you ever grown them?
Yes I love them, I grow several types of sunflowers, I am an expert when it comes to them, anything you want to know about them? 
How long does it take for them to grow to full height?
Well I grow a special sunflower called "H. annuus", and it takes about 2 years if I'm not mistaken.