Right now, I don't use any ferts at all. But if I was going to change from Aluminum sulfate to sulfur how much should I use to avoid burning if it is high nitrogen? I would have to spray it on the roses before the canker set in to get any effect, and I assume all my roses already are infected, but some of them are more resistant. I think the canker was introduced by a rose I planted that had the infection in late fall last year. If I had known sooner, I would have removed that one sooner, but now it's too late. So, if I was using sulfur, then naturally one would not also use plant food? The sulfur would feed the roses? It is so confusing.

I was only using like a 1/4 teaspoon to a gallon of water of the Aluminum sulfate and I did not do it very often, maybe twice a year, because I would forget to use it. I still have a huge amount I bought like 20 years ago and will never use it all up. I don't know if it made any changes to the soil, but it did make the hydrangeas have a more ugly looking color then using nothing but compost. I am still a big believer in compost. I wonder if sulfur would acidify the soil without changing the color of the hydrangeas? I would like that.