I purchased some of these several years ago. My husband and I do the gardening for our church. We had coleus under a large tree. I had put a pinch of these under each plant as they went into the ground. A storm came through and took the tree down. I was sure the coleus would die, but they did wonderful, never wilting in the heat. I believe the reason was the crystals, and we use them now with all of our plantings.
A tiny bit goes a loooong way.