Potassium Nitrate - Has anyone used this?

[BobInBonita]

After reading Mote's "Florida Orchid Growing Month by Month", I wanted to try Potassium nitrate as an alternate fertilizer.

I searched high and low at big-box stores, garden centers, a farm supply store, and drug stores (it used to be used in curing meats) with no success.

I searched the internet and found that stump removers are frequently Potassium nitrate. Spectracide Stump Remover was specifically recommended. Unfortunately, I found the reference on an amateur fireworks site, not a garden site. They commented that an impure form wouldn't work as well in pyrotechnics, but although I would like explosive growth, an impurity insignificant in explosives might be significant on orchids.

The first garden center I checked did not have the Spectracide brand, but did have a High-Yield Stump Remover. It was a little off-white and was in large granule form that didn't dissolve easily.

I then went to Lowes and found the Spectracide brand. It is a pure white fine powder that dissolves readily in water.

Has anyone used this form of Potassium nitrate? If not I'll try on just one or two before going widespread.