The aluminum sulphate may be too little or it may not have reached the root ball.

I used alot of aluminum sulphate...say 1/4 cup every two weeks the entire season until they bloomed and it worked for me. THis was on Nikko BLue.

Wow.... I didn't use nearly that much. I guess I need to stock up on alum sulfate. Thanks for the help!

My endless summer is starting to bloom at it is blue.

In total this year I probably put down 2/3 of a cup. I suspect that since it was blue in the pot last year, the root ball was surrounded by acidic soil which made my application less this year.

I suggest that you investigate the use of "ALUMINIUM" as it has been under the gun Re: poisoning certain plants, Re the rhodo group and some of the watergarden group. "Ferrous Sulfate" may be the better choice,however I personally don't know for sure as I don't grow blue Hydrangeas, and I would never have "ALUMINIUM" in my garden. Rai

Aluminum sulphate should not be used for rhodos and azaleas but can be safely used for hydrangeas.

I have 3 endless summers 2 blue 1 pink. I planted them in spring of 08. The colors have changed a little bit, the blues have stayed blue with a bit of lavender and the pink is a darker pink with some lavender here and there. After 3 years I figure my soil must be on the neutral side.

I asked my local garden center if I could change the pink to blue and she said "a pink hydrangea will never be blue, however a blue hydrangea can turn pink". Can someone tell me if this makes sense? Especially when the ES hydrangeas are marketed to change color?