My basic gameplan for hydrangeas pruning is - unless you really have to, don't do it if you want bountiful blooms net yr...how old is your Nikko...I didn't prune my and mom's Nikko's till they were 4-5 yrs old (and quite large - 4 X 5 feet)- mostly remove the dead sticks and cut the plant a bit back due to size contraints..the Nikkos will die back, lose the leaves and leave some ugly sticks when it goes dormant...you then can cage it with wires and mulch it with a big pile of leaves or straws and protect it from cold winter winds...it works like a charm here in Jersey (z6b)...jmho.

That sounds just right. By the way, the Nikko is new as of last month, though it's already growing like crazy. I've heard that they often don't bloom in the second year--do you recall if that happened with yours? In any case, thanks for the tips!

nikkos do bloom every year at least mine do.
give them some more aluminum sulfate to make them even more blue.
the most beautifull hydrangeas to me are; nikko and endless sumer . just gorgeous at the moment, they are sooooooooooo
blue.
good luck

My nikkos bloom every year, a trick my mom likes to do though is to apply some high phosphate fertilizers once the current blooms are done with (and the plant ready to set buds for next yr's bloom)...she uses the Viagro colorburst - around mid/late July - one good soaking and that's it...then make sure you overwinter the plant well (say you are in zone 6/6b)...dont fertilizer the plant during the fall, winter...check the soil once every two weeks during winter, make sure it is not totally dried...or else your plant will die.. pay attention to the last frost day in your area, you can unwrap the plant a week or two before the last frost date, and if the nite temps drop UNDER 40 F, YOU MUST cover up the plant with some black plastic bag the evening before - a large lawn garbage bag will do...wake up the plant with waters, nice sunshine, warmer temps, and a good dose of fertilizer - osmocote..or something similar..if you want blue blooms - drench the crown of the plant (the soil, roots, never the leaves) with aluminum sulfate solution - 1 TABLEspoon per gallon - use 1 gallon per plant (make sure the soil is moist before the drench)...repeat the drench one more time two weeks later...and that should get you blue blooms all summer (unless your soil is very loamy, clayish and alkaline - that's not a problem for Jersey soil)...I know folks apply aluminum sulfate more often - say 3 or 4 applications as indicated above - but i like to do as few as possible..my aunt in Missouri has clay and alkaline soil, she applies alum sulfate twice a season like above but...if the blooms are pink, she would use a recipe of 1 TEAspoon of alum sulfate per gallon, and applies to the nikkos once a week until the new blooms are blooming with pale baby blues..

Nikkos are very easy to grow - never let it dry out, it is not very sun and heat tolerant and will not do well with hot winds, direct afternoon hot sun..

have fun.

Babyblueyes says: "she uses the Viagro colorburst"... Did you mean VIGARO? Thanks for the giggle!

Babyblue:
I am also in NJ - 10 miles from the beach, we don't get as much snow as only an hour north or even 1/2 hour inland -map says I'm in 7a- just bought a Nikko that I will plant in the fall on the east side of the house = gets morning sun, afternoon shade, ideal for hydrangeas, right? Can you help me with the winter protection thing. I've read that in zone 7, you do not need to do it but I want flowers. Do I cover the whole plant? and how do I find out my frost date - I'm guessing around Christmas.