The Portland Dahlia Society allows members to borrow a very nice Ph meter to test their gardens. It cost about $125- and gives results in a few seconds. Members find that their soil does vary in Ph from location to location in their gardens. Here in Western Oregon our soils are generally a bit too acid and the addition of lime does wonders for dahlias. I have read that dahlias prefer acidity of about 6.5 but I have noticed that they do grow reasonably well at 6.0 and above.

Well, the test itself was free, but came back with a pH reading of 8.5 - Yow! (This exercise is no longer free - I will be spending money on soil additives.) I find this interesting because Michigan soil is normally a bit acid and I amended with loads of Canadian peat about 18 mos. ago. I think I'll do an independent soil test myself (another outlay of $$$!). The Colorado Dahlia Society recommends Aluminum Sulfate (among other things) to lower soil pH and indicates how to apply it. Does anyone have experience doing this? Results?
Thanks