My Spuds have long very greenery

Hi  - I have had my first try of spuds this year an my 2 new gardenshares. They seem to nbe cropping ok on the new spuds I've dug up but they have awfully long greenery... some are about 5 foot long and they all seem to be smothering eachother..

I prepared with general fert and dug in some horse manure.. then dug a trench about a 8 inches deep, planted the spuds and then earthed them up about a foot above ground when they popped up.. I have various types planted as I did'nt know there were earlies etc. just bought from towna and planted..

Any ideas on the long greenery?

It was ne manure so will prepare now for next season... they are good tasty spuds though...