Question
I live in Michigan. I have 3 Endless Summer hydrangea bushes and I hydrangea tree. They were planted by professionals. This is the 3rd summer for them. They are very sparse with thin branches and the flowers are not very pretty. I have never fertilized them. I did cut them back twice in the fall thinking that would thicken them up. What fertilizer should I use? Any suggestions to what I can do to strengthen them?

Answer
Hello Chris

Hydrangea are usually very easy plants to grow as they don't suffer many problems with pests or disease.

Cutting them back will usually thicken them up with really good leaf growth in the following year, but no flowers until the year after that!

As this doesn't seem to be happening for you, lets look first at the growing conditions.  Hydrangea like a place in dappled shade and lots of water.  In full sun they will tend to droop during the middle of the day, and recover in the cool of the evening.  If your plants are in full sun and are also suffering from lack of water, that may have lead to the sparse growth, because they will be stressed all the time.

So what to do?  I don't know how old, or how big, your plants are, but if they are quite small and young (and in full sun), you could opt to move they to a shadier spot.  

However if moving them is not an option -

First - make sure that they have plenty of water, especially during dry spells.

Second - at the beginning of the growing season in about May next year, give them a really good feed with what is called a balanced general fertilizer in liquid form, to get it down to the roots quickly.  This will be available in any garden center.

Third - put a mulch of well rotted organic matter around the base of the plants, spreading out about 2 feet #this will not only feed the plants long term, it will also stop the moisture evaporating around the roots.

Well rotted organic matter could be leaf mould, home made compost or, if you can get it, well rotted animal manure - horse manure is the best!

Finally - don't prune for a while!  Hydrangea flowers on growth made the previous year, so if you prune in the fall you are effectively destroying next years flowers!

I do hope the above works for you and you get a better display next year.

Gill