Q.My Endless Summer Had Only 4-5 Blooms All Summer. Now In October, Every Branch Has A Bud ! I Live In Michigan, So There’s No C
hance they will they will bloom. What should I do with them? I do not prune it.
By the end of October or the start of November, Royal Oak tends to have overnight temperatures in the 40s and that, along with decreased temperatures, will reduce the chances that some of these flower buds may open or open fully into flowers.
The problem with ES is that it does not begin to open the buds early. To bloom from new wood, ES has to let the stems get tall (3-5' high but, the height varies based on many factors) and old enough to produce/open flower buds. Cultivars from the Let's Dace Series are more compact (2-3') and so they do not require waiting until the stems are as tall as ES's; those varieties may make better choices in locations like yours.
However, an even better choice would be to use Smooth or Pee Gee Hydrangeas. These will bloom earlier and not have this blooming issue. Of course, these types of hydrangeas do not produce the same types of blooms or the same colors as ES mopheads/lacecaps.
Going forward with keeping ES, I would consider fertilizing it with a fertilizer brand that is slightly higher in nitrogen and more phosphorus to see if this may trigger a faster/earlier stem development/growth that gets tall sooner. Or have an application of the current fertilizer in mid to late spring and another two months later but before the last week of July (that week is your average date of first frost minus three months). Then see if that helps your ES in any way. I wish I could still contact this acquaintance; I was now wondering what fertilizer program he was exactly using (what fert, how much and when he applied it in Ohio). His macrophyllas would normally bloom late summer to early fall (or about now). Try not to go overboard with higher nitrogen levels as too much nitrogen can stop blooming. A few percentages 1-3 may be ok; increase phosphorus a tad more. Michigan is located further north so this may not work for you but you can try if you wish.
You can leave the blooms that are open and the ones that are in the process of opening "as is". Enjoy whatever blooms you do get. All of mine are officially brown so I only see new ones from friends in the United Kingdom where some varieties of macrophyllas are still blooming. If your plant aborts the blooms/buds due to reduced sunlight or cold temperatures, these blooms/buds will prematurely turn brown. You can always deadhead them at any point (cut the peduncle string that connects the bloom to the stem).
If these stems typically dry out during winter and die for you, you can prune them all the way down by the end of May or thereabouts (live/green stems should leaf out by then). When the stems do not come back every year, some people cut them down in mid/late fall or in winter too but, since pruning now can force new growth that can get zapped by early frosts, I prefer to prune in the spring instead.