"If the old wood is not surviving are they going to continue to struggle?" Yup. 3a is really too cold to expect them to bloom much if they haven't had winter protection. So either pot them and overwinter in the cold cellar, or do a search on this forum for winter protection to see some strategies of what you can do to help them overwinter outside.

Endless Summer is a hydrangea macrophylla and these are not too winter hardy. They should bloom in the Summer also but in very cold areas I notice that people complain about a lack of blooms. Winter protection typically works but in Zone 3 I would bring them into a cellar instead.

The other ones that you have are hydrangea paniculatas or hydrangea arborescens and they ARE winter hardy down to Zone 3; plus the also develop flower buds on new wood during Spring and bypass all the problems that a Zone 3 winter has.

Here in MN zone 4b Endless summer is a bust too. They sold them liberally a few years back but it was a total fabrication of what one can expect. If we have a very long and mild Fall, two of my three may have two or three blooms by October. I moved mine trying to find the right sun/shade ratio and where they are now they do not wilt in the afternoon as in the past. They just do not bloom. If it were worth the trouble I would dig and trash them but they fill the bed and provide something in front of Annabell.

I had good results in MN Zone 4. East side foundation planting. The last rake of the fall, sometime in November, I piled leaves up on them and left the stems up for the winter. When I moved I chose to plant Bloomstruck instead as it seems to hold up to more sun and dryness better.

I also do fine most years with Endless Summer, so I think it's a bit fussy about growing conditions, but in zone 3 it really is pushing zone tolerances.

I am betting that with ever increasing warmer temps through all our winters (CLIMATE CHANGE) it won't be out of the question to have ES flower its brains out in even....Alaska?

I think I will just pot them at the end of the year. It is not fun waiting for the no show flowers. Mulching them is keeping them alive but not getting me blooms. Thanks for the advice.

Hello, hello, i am wondering how you are doing with endless summer hydrangea in zone 3? I am searching for this topic, I got 3 endless summer this spring, they are doing really great in my zone 3 (Edmonton) garden so far, growing big and flowering nicely. I am searching though how to get them through the winter and hopefully they can bloom next year, :)

Any tips would be greatly appreciated! Cheers!

@luis_pr Thank you so very much for the info! I have seen people plant ES on the ground in the spring and dig up and put in a pot and bring inside for the winter. For me, it is almost not possible. 1, the plants are very big now, 3 ft wide and tall, as I bought the 4 gallon ones in the spring. oh well. 2, too much trouble for me and too much shock for the plant. 3, i dont have indoor space and big enough window to give them the light to keep them happy insdie. Artificial light is too much set up again.

SO after some search, i will be use the cardboard box method, i think. Here are tentative steps: please help me better this process if something wrong in the procedure lol.

Zone 3/4, Edmonton

1) After tree leaves fall, collect leaves in plastic bags.

2) When ES hydrangea leaves are brown and dried, covered them with a cardboard box, fill in dried leaves.

3) Tape the top of the cardboard box, to seal.

4) Secure the bottom with rocks or garden staples.

5) Wrap the box with brown burlap.

6) Wrap again the box with black landscape fabric, to absorb warmth from the sun.

7) Sit for the winter to be over, hopefully lots of snow cover.

8) Remove protection around last spring frost, on May 15 ish.

9) If Frost come back after the fact. using white drop cloth for temporary cover.

I also attached a pic of my blue ES (the original) in my yard this year.

Isn't this blue out of this world!