Nikko Blue is famous for its blue blooms innacidic soils but there are others too. To get the same one, ask for several cuttings and use them to propagate. That way you are assured to ”that” one.

I find Nikko Blue produces a very washed out coloring. Not at all a very deep or intense blue. IME, Enziandom (aka Gentian Dome) produces very intense deep blue flowers. And big ones!!

My LA Dreamin has a more beautiful blue than my Nikko Blue, Bloom Struck, Penny Mac, and Nantucket Blue, but for the deep blue the Proven Winner's Let's Dance series like Rhythmic Blue and Rave might be possibilities. There are also the older varieties like Blue Danube, Mathilda Gutges, Hamburg, Altona, and Enziandom. I think most need acidic soil to get that deep blue.

@ nicholsworth Z6 Indianapolis, beautiful! I think that is a generic florist hydrangea. Costco does sell Endless Summer varieties, but those are clearly labeled and the leaves are different. Generic florist hydrangeas are meant to last and rarely flower if you plant them in the ground. You should put the hydrangea in a larger container with potting soil and continue to overwinter it in your garage. Also, it might benefit from being fertilized with Holly-Tone in the spring. You can learn more about these generic hydrangeas here: https://delawaregardener.wordpress.com/2024/04/11/florist-vs-landscape-hydrangea/ 

If you live in a suitable climate zone, florist's hydrangeas can definitely be transitioned into a landscape planting. A friend's collection of garden hydrangeas all came from Costco or grocery stores and in full bloom. But a zone 6 is questionable for a non-remontant or old wood flowering hydrangea macrophylla in the ground..

btw, an organically sourced fertilizer like Holly-Tone is not very effective in a container setting. Just not sufficient quantities of soil microbiology in potting mix for them to be efficient.

Thank you everyone for your very helpful responses, pictures and suggestions.

@luis_pr and @gardengal48 (PNW Z8/9), I planted a very small nikko blue three years ago. It has grown now and is making flowers, but they are not the intense blue i was hoping for. I did manage to make the soil more acidic, so it is more toward the blue/purple side. I am going to add more aluminum sulfate to the soil now I that i am reminded of it. @gardengal48 (PNW Z8/9), what I saw looks similar to Enziandom. I might have to get one. @luis_pr, thanks for the suggestion to ask for cuttings. I might work up the courage to go ask :) Havent made hydrangeas from cuttings, so it could be a fun adventure. My annabelles are going nuts, so I am thinking of taking cuttings as well and making more.

@floraluk2, I can make the soil more acidic. It was gardengal who told me how to do it in a different thread a while ago. I have a altona that I was able to shift toward purplish pink (it was super pink last year).

@chrysalids, LA dreaming looks beautiful. Is yours multi-tone or did you manage to make them mostly blue?

Dorian, most PNW soils (those west of the Cascades) are sufficiently acidic enough to produce blue flowers on hydrangeas that lean in that direction. In fact, they are adequately acidic to support any ericaceous or acid loving plants - blueberries and other vacciniums, rhodies and azaleas, pieris, heaths and heathers, etc.

But it never hurts to apply some aluminum sulfate to assure aluminum levels are adequate for the hydrangeas and to maintain acidity even in container plantings.

@ Dorian W, the blooms on my LA Dreamin hydrangeas are blue and purple (no pink) which I love. They are in large containers with potting soil. I didn't add any soil acidifier so maybe the potting soil might have been more acidic than neutral.

Oregon Pride, Walmart "florist", Let's Dance Sky View, Spike, Zorro.

Many show stress from heatwave. Black stems on Zorro are to die for, better than the flowers IMHO, but the flowers are pretty great too.

Also, behind Spike, you can see Dichroa febrifuga photo bombing.

Dorian, my soil will never be acidic whatever I add. The underlying rock is limestone. Our water is very hard. I have to grow blueberries in containers of ericaceous mix. As an experiment I tried them in the ground but copious additions of acidifiers made no difference.