I just started growing delphiniums in my cottage garden bed and I must say, I am intriqued by this plant. I do prefer the magic fountain over the pacific giants.

You must be congratulated on having a delphinium that old which means you've been doing something right.

Anyway, I learned that old established delphiniums should be limited to having only 5 flower stalks otherwise it would over produce and bloom itself to death. These are heavy feeders too and would profit on early spring fertilizing.

Here's a useful link for more information.

http://www.mrsgreenfingers.co.uk/delphiniums.htm