First of all, thanks, Todd for mentioning that it is toxic to Rhodies. Now I know why mine have been languishing! I had used some a few years ago to try to make the soil more acidic for them--oops!
But, I am wondering now, about the wisdom of adding aluminum to soil in any case. Is it something that we will be considering a pollutant in years to come? Is there any scientific evidence or concern about its use in the landscape?