Many of macrophyllas for sale usually get 5-6' in height. But, it usually takes abou 10 years or so to achieve their advertised height/width.... although in places with a long growing season (like here in TX), it may take less time. Just look at the plant label's height/width to make sure it will work for you. Many of the Endless Summer Series Hydrangeas and many of the Forever and Ever Series will work for you. And they are commonly sold here at Lowes, Walmart and others.

No pruning, a stable water regimen and high nitrogen fertilizers (blood mdeal for examlpe) will also help accelerate grow. Just don't go overboard. Do not overwater as this can cause fungal diseases or root rot. And do not overfertilize as you can end with nice lush green leaves and no blooms.

Sunlight will help produce bloomage based on "how much" sunlight the shrubs get so, lots of sun can yield lots of blooms and so forth. Too much sun here in TX and the blooms can brown out. Too much sun here and the leaves can suffer as well (especially in our awful summers). Bright shade will not produce the maximum bloomage but it still produces plenty. Dense shade is the one that can be a problem. Aim for 4-6 hours of sun and shade by 12pm (here) although less works too.

If your shrubs are in bright shade, they will be ok. I have most of my hydrangeas on the north side of the house too and they bloom very well. I also periodically check the levels of nitrogen, potassium and phosphorus regularly with one of those cheap soil testing kits, usually sold in Spring over here.

If you still want something other than ES or if you want more hydrangeas, look at the plants offered for sale in April-May this year to see what strikes your fancy. They will be blooming so you can verify that you will like the shade of colors and the blooms. Note: Lowe's brings a limited number of hydrangeas to this area in March (maybe 1-2 varieties only) and then in April, it brings a whole bunch more.

Annabelle (and its cousins) does well here. In bright shade, it will maintain its green color longer before it changes to white.

Oakleaf hydrangeas also do very well here but read the labels; some of them grow to 10' tall so make sure the oakleaf hydrangea that you choose says it will be around 6' or so. Examples: Munchkin, Ruby Slippers, Pee Wee, Sikes Dwarf, Vaughn's Lillie and Jetstream. I have a Ruby Slippers under a Chinese Pistache Tree.

Paniculatas are also another choice. But many also get large so just check the labels' height dimensions and look for 'dwarfs'.

'Dwarf' versions of paniculatas and oakleaf hydrangeas will get 3-6' in our long growing season.

Luis

I am looking to plant these in Houston as a hedge along a fence for privacy. When is a good time to plant them? Now or wait until spring?

Fall is a good time to plant. Just pick a time when the temps have gone down to the 80s. Prepare the hole first and add 3-4" of organic mulch.

You can also plant during Winter since we have mild winters and the soil does not freeze.

And yes, Spring would also be fine; if you do choose to plant in Spring, place the shrubs where they will be protected during winter and water them once a week or once every two weeks (basically, do not forget to water them just because they are dormant).