Hello, Terry.

I typically do not worry if I get no blooms on the first growing
season as I prefer that the plant develop a good root system instead. But if your description of your zone is correct, I may have bad news. Northern Minn (USDA Zone 3) is too cold for ESs or any type of hydrangea macrophylla for that matter... :o(

This would result in poor blooming and even plant (root) death. I am not sure if the roots of a hydrangea macrophylla can withstand Zone 3 winters (since the originators of ES say it is not hardy enough) so please consider growing ES in pots or -better yet- growing hydrangea paniculatas as these may provide more reliable blooming.

ES is advertised as being hardy only up to USDA Zone 4. See ES and zone info here:

http://www.endlesssummerblooms.com/the-collection/the-original

http://mynortherngarden.com/2012/01/25/big-changes-for-minnesota-in-new-hardiness-zone-map/

Know that you have company with blooming issues though. A lot of people post questions about ES not blooming at all in zones lower/colder than USDA 6 so, you are not the only one.

Like I said earlier, I normally would not worry about lack of blooms. But still, on year one, no bloomage is a bit odd as plant nurseries want to display the shrubs with blooms so customers will buy the plants. If your plants were leftover inventory from last year (2015) that you bought in Spring 2016, bloomage in Spring 2016 may have been wiped out by weird weather that we had thanks to El Nin~o. However, I would have expected ES to bloom in the late Summer though.

But you know what, I would have expected the plant nursery to sell ES as an annual in your zone. Are you sure that mopheads like ES can grow as perennials where you live? Or are you sure of your zone description? Have you seen other growing ES (mopheads and lacecaps) where you live?

I remember that, in this last Winter of 2015-2016, some places were just too cold in 2015-2016 Winter. Other places were too warm and other places got cold, then warm and then cold again... something that could have broken a hydrangea's dormancy, made the shrub go into 'grow' mode when it got warm and then the cold killed the stems and the flower buds before you bought the plants.

Then in Spring 2016, they probably woke up and started growing new stems from the base. As a result of cold-warm-cold weather over the winter months, the plant has no way to produce early Spring blooms and you get no "early" Spring bloomage (although I suspect even on a normal winter, you would not get early Spring bloomage anyways... too cold)..

The hydrangea stems normally develop invisible flower buds at the end of the stems in July-August and these normally open in the Spring. So last year, in July-August 2015, your ESs -while at the plant nursery- should have developed invisible flower buds and the 2015-2016 winter probably killed the stems. In Spring 2016, the plant then developed new stems, leafed out but, these would not develop flower buds right away. That would occur later, in the late Summer months...

So, sometime in the Summer of 2016, the new stems would have developed flower buds again. If all went well, one has to wonder what could have prevented them from developing or opening in the Summer.

The worse news is that a lot of people have posted before that they too are not getting bloomage from ES after waiting for several years. This typically is reported by people in Zones 5 or colder. For people in those locations, I usually suggest to give them 1-3 years to develop a larger root system and become established in the garden and yank them if nothing happens. But, I am especially concerned about how the root system will do in such a cold zone as you describe. Which I assume is Zone 3.

So, here are other causes for no blooms in no particular order:

Pruning live wood in the summer, as the shrubs are about to develop these invisible flower buds, makes you cut off the invisible flower buds that the plant develops in the Summer. Not good so try not to prune stems that are alive. It is 'ok' to prune dead wood that has not leafed out by late May though.

Too much fertilizer can keep the plants in "grow" mode, so much so that, they produce nice, dark, very healthy looking green leaves... and no or few blooms. Your plant may have had fertilizer pellets already and if you added a lot of fertilizers with high nitrogen levels, that may have done it.

Try a single fertilizer application per year. Say, a 1/2 or 1 cup of cottonseed meal, organic compost or composted manure when they leaf out in the Spring. Optionally you can add liquid seaweed, liquid fish or coffee grounds but stop all fertilizers by the end of June so the plants will go dormant at their appropriate time.

If you cannot find these, you can use a slow-release, general purpose, chemical fertilizer with a NPK Ratio of around 10-10-10. The first number is the one for nitrogen so look for a chemical fertilizer that starts with a number around 10. For example, 30-10-10 would provide too much nitrogen. Apply the chemical fertilizer per its label instructions and stop by the end of June.

If the plants are in dense shade, that can inhibit flower buds production. If they are planted under a tree whose roots compete for water and food, that can affect bloomage too.

Hydrangeas like soil that is evenly moist. Soil that dries out, is re-wet, dries out again can make the plant abort flower buds. Mulch up to the drip line is useful making moisture last long. Give them about 1 gallon (3.8 liters) of water per watering if the soil is dry.

There are pests that can eat the flower buds when the buds open. Watch out for squirrels, bunnies, deer. Some eat the flower buds; others eat leaves and flower buds. Sometimes they just eat leaves. These could have impacted bloomage in the Summer.

To reliably get bloomage, you may have to go out of the way and very heavily winter protect the shrubs or grow them in containers and bring them into heated/protected rooms during winter. Even better, I would recommend using varieties of hydrangea paniculata as they are more winter hardy (to USDA Zone 3).

Paniculatas develop invisible flower buds in mid-to-late Spring to early Summer. So frosts and winter issues are normally a problem for them. Examples: Bobo (very compact), Little Quickfire (compact), Little Lime (compact), Quickfire, Limelight, Pink Diamond, Pinky Winky, are some examples of good paniculatas.

I would also go back to the plant nursery to ask what they were thinking of by selling ES there (unless it was in the section where they sell annuals). Or perhaps your zone is actually warmer than typical Zones 3 of northern Minn???

If you decide to keep ES rather than return it to the nursery, you can transplant it to a large pot to bring into a garage that stays warmer than outside or a cold basement. If neither a cold (but heated) garage or a cold basement is available, it has little chance of survival as Luis has said.

Others have commented that the H. paniculatas will grow slowly at the northern end of their range and perhaps stay smaller as far as ultimate size, so if you decide to grow them, consider that as well. They are great plants.

Thank you very much for the replies. I am very pressed for time at the moment and will post ASAP. Thanks for taking the time.