I have an established ES that is blooming as we speak but is getting too large. I would right now like to prune the offending stems but I don't want to very adversely affect next year's blooms. I know it blooms on old and new wood but after doing too much pruning 2 years back I got almost no blooms last year i.e. old wood is where it is at!
So I am thinking that these new too tall stems are new wood and so cutting these back rather than ones with the blooms is safe...do I have this right?
I don't understanding pruning "Endless Summer"
Worrying about the stems may not be necessary if you do not winter protect. In Zone 5, these stems will most likely not survive your harsh winters and will dry out. If so, feel free to prune now. All growth should be originating from the crown in Spring every year so all the stems can be considered new wood.
However, if you winter protect the plant then you will have both: old wood in the form of stems (from previous years) that survived your winters. And you will have some new wood in the form of stems that grew all the way from the crown this last Spring. With this mix, you can prune at any time but you need to be, just a little careful, to time the moment. For example, if the plant already bloomed, you deadheaded about 2 weeks ago then ES is preparing to bloom again but the flower buds may still be invisible; pruning will cut off new blooms and you will get no flowers until the next flush.
Problem is... when you get stems that are out of sync with the rest of the plant, one feels compelled to prune them for aesthethic/safety reasons. I get that with roses suddenly throwing a long branch out of the blue. It would be ok to prune these now regardless of whether the stems are new wood, old wood or confused wood. Let the other unpruned stems do the blooming.
If the unpruned stems have spent blooms, you can deadhead them in order to encourage more bloomage from the unpruned stems. Do not fertilize again though. The initial fertilizer application in Spring will cover the whole year for your zone and will help the plant go dormant at the appropriate time for your zone. Too much fertilizing and the shrub starts producing nice lush green leaves at the expense of blooms. Use "the end of June" or "sometime in July" as a general marker to tell when to stop applying minor/weak fertilizers like coffee grounds.
For a discussion on deadheading versus pruning, see http://www.hydrangeashydrangeas.com/pruning.html
Deadheading is covered in 'Pruning: Method One', under 'Removing Old Blooms'.
Luis
Excellent post "Luis"....thanks for your time.
Here is what I mean. See the taller shoots? My plan was to leave existing stalks currently having blooms and instead prune away these flower naked new growth stems.
I didn't realize that Endless Summer would get as large as mine has. It's now about 6' X 8' wide and still growing. It is going to get a major pruning this year or I won't be able to bet in my garage. Right now it sets off my backup alarm when I back out. LOL