These delphiniums are Pagan Purples, one of the New Millenium varieties. They are about 6-7 years old, but I have moved them a few times. They really are supposed to be only 4-6 feet tall. I do not fertilize any of my gardens other than with compost or composted manure every couple of years. I can't figure out why they get so big. I should try some of the other hybrids to see if they perform the same or differently.