Answer: The good news is that Iris are relatively tolerant of soil pH. I've grown them in Washington State where the soil is acidic (5.5) and in Arizona, where the soil is alkaline (8.0) without problem. Your soil tests out at nearly neutral, which is fine, too. Instead of trying to lower the pH with sulfur, you might try mixing in some peatmoss as you plant your irises. This will lower your pH by just enough to put it in the slightly acidic range. Hope this clarifies things for you!
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