Something acidic - I think aluminum sulfate is most common.There are acidifying fertilizers you can buy for azaleas, etc...

Aluminum sulfate has tended to fall out of favor as a soil acidifier. It can leave too much aluminum in the soil, which is not at all helpful. Straight soil sulphur, while somewhat slow-acting, is perfectly safe, easy to use, and will last longer in the soil. If in a hurry, that careful application of mild acids can get you there-things like vinegar. The use of ammonium-based fertilizers will tend to drive down soil pH over time also, this resulting in a more acid reaction, as will urea. Nitrate nitrogen, on the other hand, tends to drive the pH up higher still.

+oM

I use espoma soil acidifier.

Hi Pug,

Reblooming depends upon the variety. Most are not rebloomers, but some of the newer hybrids are. If you have the old standard Nikko Blue (which can appear pink - mine do), those bloom only once on last year's growth. They are just now starting to put out their flush. Other varieties like Endless Summer, Twist and Shout, and the hydrangeas in the Forever and Ever series are rebloomers. Some of them rebloom on old wood; some on new growth.

Good luck with yours. It sure is pretty! I love pink blooms... and I love blue ones, too!

Carol in Jacksonville

Thanks all for your replies and help :o)

Maybe I'll just let it rebloom pink ( it is a pretty color) and not add anything different to the soil...I got this as a very tiny 3" plant ...with only 4 leaves when I received it...it was a rescue from a neighbor lol...Never though I would actually get it to bloom, so very unexpected.

Do I need to prune it back a little after the blooms die off so it will rebloom next year (if I'm lucky again)?

I've got on e of the 'Endless Summer' cultivars-the original one, for whatever that's worth-and I hated that particular shade of blue. I like blue flowers just fine, but something about that shade seemed garish and harsh to me. So in any case, I've not acidified the soil at all and the plant's blooms are now in a much more organic, satisfying shade of pink. since this is a cultivar capable of blooming on new as well as old wood, and since I'm doing my gardening in a slightly colder place than Florida, lol, I just wait until all cold weather is done before pruning mine back a bit, mostly to tidy it up a bit and keep it in bounds of the rather tight spot its in.

+oM

You do not need to prune for it to bloom next year. In fact, if you prune too late (generally after July/August), you may not get blooms next year - - because it blooms on prior year growth and you may have cut them off. Of course, if you have a rebloomer, this is a moot point. :)
Here's a good article:
PRUNING HYDRANGEAS

Carol

Thanks Carol! Appreciate the link...