Well my hephalump garlic didn't reach 5 foot, but it was the only garlic on my plot that remained rust free! From the 8 cloves I planted I harvested 4 proper HUGE garlics plants with seperate cloves, altho only about 5 or 6 per plant, but the other 4 didn't bulb up so were just like huge garlic flavoured onions.
I am going to grow it again as it is good for roasting or making dressings with, as well as for use in regular cooking. In my opinion, it has a milder sweeter taste, almost sticky. When I do my roast veggies I use a clove and just cut it into segments, they are so lovely and big, one clove goes a long way!