Connie, I would wait until after frost danger has passed. Good Luck with Nikko Blue. I had one for 4 years and it never bloomed, checked with a local nursery and they told me that Nikko Blue is not hardy in MN and would probably never bloom here. It finally succumbed two winters ago.
I will be interested to see if yours fares better.

Linda

Hi Linda,

Thanks for the info. That's what I get for not doing research and falling for the pretty pictures on the package. I think I'm going to take it back and get an Endless Summer. I was reading up on the Hydrangea board and it looks like those fare better in zone 4. Since I'm a beginner,all the overwintering stuff on the Hydrangea board looked like too much of a commitment! =)

Connie

I've grown Nikko Blue for 4 yrs. in Mpls. With LOTS of mulch ( I build a little chickenwire fence and add leaves to the top) it has bloomed 3 of those years. Endless summer, on the other hand, does seem hardy and carefree.