I suspect it is an Annabelle hydrangea or one of its cousins (Incrediball, etc), not a panicle or paniculata hydrangea. These arborescens hydrangeas prefer either morning sun only, dappled sun or bright shade. And they have serrated, large leaves and either mophead or lacecap blooms. They tend to bloom in mid to late Spring. The blooms are either white (whites may be preceeded by immature greens for a week or two), pink or lime green. Due to the time and the blooms' form, I do not think it is a paniculata.
Paniculata hydrangeas are the most sun tolerant hydrangeas and perform best in full sun (except in very hot locations, where they can grow but be poor blooming choices). Down here, blooms prematurely abort due to the heat. I would also give paniculata leaves a little afternoon shade in my extremely hot summers but elsewhere... oh, they will be fine in full sun. Paniculatas hydrangeas have panicle shaped blooms and smaller leaves than Annabelle. Paniculatas tend to bloom later too: mid to late summer. Some paniculata blooms have a small scent and that can attract pollinators like bees so, do not plant them very close to the front door of the house.
If either arborescens or paniculata is planted in bright shade, the blooms may be affected depending on how much sun they actually get. For example, on some years, my Little Lime (a paniculata) and Annabelle (an arborescens) -planted in bright shade- have produced blooms that stay lime green throughout the whole growing season.
Annabelle and its cousins may spread via suckers in Spring. Their blooms start green, quickly turn white (or pink or lime green on new varieties), then lime green, then they may get some pink/red/purple splotches and finally they turn brown-ish... around December for me but much earlier than that in NJ. Oddly, I saw some Incrediballs here that started green and then turned white, green, light sandy color and brown. Not sure why though. Maybe the intensity of my summer temps had something to do with it as we had daily 100s at about the time it turned sandy.
Hydrangea arborescens, the technical name for Annabelle and its cousins, is soil moisture sensitive even for hydrangeas. I managed to kill one specimen during a dry winter when I turned off the drip irrigation during a long freezing time and forgot to turn it back to "on". All the other hydrangea varieties leafed out. That Annabelle did not leaf back and had no new growth... although I kept it watered "dead and all" for one more year just in case.
Note: there are some pink-ish versions available of those Annabelle cousins. They stay pink throughout the growing season, with maybe a little pink variation as the bloom gets older. The pink color cannot be changed to blue by planting in acidic or alkaline soils although someone told me that the shade of pink may change by a tiny amount in alkaline versus acidic soils.
Buy Annabelle and its cousins while in bloom to make sure you are buying the one that you want. These arborescens are similar looking.... Some produce pink blooms and others produce lacecap blooms. Also, check the shade of the pinks. You may or may not like the shade of pink so, see them blooming to make sure that you approve.
Annabelle and its cousins are very winter hardy, to Zone 3 (same as hydrangea paniculatas).
The Scott Arborettum in Swathmore College has a hydrangea collection. The collection is (or used to be) located along Whittier Place, across from Papazian Hall.
