On pruning....
Your Nikko Blue & Endless summer are H. macrophylla hybrids which, almost without exception will die back to the ground each year in 5a (-21ºC is about as low as the stems will handle). The Nikko Blue flowers on last year's wood so you will probably get minimal flowers. Endless Summer blooms on old and new wood, so while it will still die back to the ground, you'll still get flowers. Prune them only enough to remove dead wood.

The Pee Gee is a H. paniculata hybrid, flowering on new wood and hardy to zone 3. Some people prune it in late winter down to branch stubs which grow very long & very fast, culminating in giant flower panicles that droop over because the stems aren't strong enough (especially in rain). Others go for a 'bushy' look and only prune to maintain shape (also in late winter). This will result in a plant with many more, but smaller flower panicles...Your choice.

Others to try...H. arborescens (hardy with white corymb (flat top) flowers) & H. quercifolia (marginal hardiness with big oak shaped leaves & white panicles)

Simon

I grow pee gee hydrangea limelight which I have to say is my most favorite plant. It's now in it's 4th season and has so far been has always produced these huge spectacular blooms. My preference is to trim off the dried/dead blooms in mid spring. If you are uncertain on what to do, let the plant be until it produces it's side buds on old wood. Then do your pruning just a few inches above where the growth is. The new buds will develop in to stems and bloom in the summer.

I also own a nikko blue which does require a bit more of protection for winter (borderline zone 5). I also do my trimmings in the spring. Again I treat it in the same manner as the peegee.

Apart from that, I had a Hydrangea quercifolia 'snow queen'. I'm afraid mine didn't survive my stupidity in which I accidentally uprooted it one spring time. I can at least tell you that it does die back to the ground in winter. Great foliage too. Much regret there.

I also own hydrangea annabels which are great and can pretty much be left alone.

Last I own several climbing hydrangeas which hasn't yet produced blooms for me. However it doesn't bother me because I like it for it's wood texture. It's now in it's 3rd year - maybe this year it will bloom.

Ianna

Thanks for the help. I'm going to print and save these suggestions. Wish me luck!

I also have a climbing hydrangea. I had it for about 5 years before it finally bloomed. It is slowly making its way across a wood fence. Lovely!

I pruned last years branches off my niko, I thought they were dead. Will it bloom this year?

Hi claysoil:

Is your soil actually clay as in your nickname? That will not be the favourite growing medium for some hydrangeas. Many prefer looser, acidic soil. Acidity (PH) is really important when you are interested in the blue flowering types. You may want to amend your soil with that in mind.

Cheers,
MG

Clairdo2...If there was no sign of growth on your Niko branches by early May, the branches are likely dead.

Niko will only flower on last years growth which in Ontario, dies virtually every winter. H. macrophylla stems die around -21ºC or so in our climate and it sprouts back from the roots every year and doesn't flower.

With protection (snow, leaves, etc.), it is possible to get at least a short portion of the stems/buds to survive and then you'll get flowers.

Try 'Endless Summer', it flowers on current year growth so it doesn't matter if it dies to the ground.

Simon

Well I have this niko bought from Home Depot a couple of years ago. It doesnt' die back to the ground and produces now buds from last year's stems. This year the stems are mostly viable with lots of leaves. I'm hoping for a more bloom production as opposed to last years modest display. It was planted in a north east location beside a fence which could probably be the reason for it's remarkable growth. In winter it receives a deep blanket of snow which adds insulation.

The protective snow cover is the key (at least one of the keys)! If all of Southern Ontario was lucky enough to get deep reliable snow cover, we'd have Niko blossoms every year. Unfortunately, such conditions are now very rare here in Kingston.

Simon

I'm in zone5b north of Toronto. We do get pretty strong winter winds, snowfall and all that during winter but for some reason my borderline plants have survived. Not just the nikko blue but also my bourbon rose and the rose is pretty prolific right now. Looks like lots of blooms coming this summer (keep my fingers crossed). The nikko is pretty much sheltered against the wind but the roses aren't.

Can you not create a micro clmate for your nikkos during winter? I've seen it done with majoo bajoo (bananas) in vancouver, whereby the plant is kept insulated in crates and straw after the first frost.

Ianna

Yes, that method will work. In fact, any method you can come up with that keeps the stem temperatures above -21ºC during an Arctic blast will work. H. macrophylla also doesn't reach maximum hardiness until late December and looses it quickly again in mid-March so temperatures somewhat warmer than -21ºC could do it in if it comes early or late season.
That drop dead temperature (quite literally) didn't come from thin air...Michael Dirr out of University of Georgia (probably THE Hydrangea expert) did all sorts of tests (lab & field) on macrophylla temperature tolerances then wrote a paper about it.

Simon

Great information. To answer MG's question, I have actually amended the soil for a few years, so it isn't too bad. I keep trying.
I'm a bit concerned about the Nikko's. I'm looking for hardy plants, that don't require a lot of TLC. I'll see how things go this winter.
My Endless Summer plants likely got hit with frost...some leaves and flower buds turned black. I pruned off the dead stuff. Hope they rebound. I probably planted them too early...but darn it all...it's Spring, and I can't help myself!

If you wish a low maintenance hydrangea, Annabelle is the best. It produces flowers from old and new stems. I've a small yard, but I've crammed it well with many plants including all my hydrangeas. Second to Annabelles, I love the regular peegee hydrangea and next to that is the limelight Peegee hydrangea (which I adore the most). All three described a low maintenance plants. They are very hardy and by the way, I have heavy clay soil which I've amended with compost, builder's sand and put composted manure yearly. The soil is very rich now. All you need to do with the peegees is to let it bloom and deadhead only in the following year. The branches will produce new buds and almost all start producing heavy large white blooms. Very spectacular.

Because my nikkos were planted in an area that provides a lot of winter protection it's thriving. It is currently producing a lot of flower buds. However, I find that I don't do much to maintain it, didn't do any prunings at all. In fact to compare with my peegees, I had to do more work with peegees than the nikkos. The only thing I neglected to do is to add any aluminum in the soil to keep it's blooms blue. It will produce pink blooms this year.

Ianna

Hi,

My soil is clay too. My climbing hydrangea has been barely alive for about 10 years and is only getting a branch longer than 2 feet this spring. My Nicko died. My pee gee seems to die back more each year and is not larger than the size I bought her at about 7 years ago. However, the Annabelle is a monster and conquers more territory each year. (Not that I really mind - she's spectacular.) All this to say I highly recommend the Annabelle.

Mary