I just noticed my fruit trees starting to bloom and the weatherman predicting a frost this weekend. It used to be I'd try everything from plastic to sprinklers to save a little fruit but then I had an oldtimer tell me a trick to saving fruit that sounded more like an old wives tale than fact. He said "All you have to do is to hang some junk iron in your trees and the frost won't hurt them". Well, I had to try it the next time my trees were threatened and decided to do some experimenting with other forms of iron since that seemed to be the most likely variable. I sprayed several trees with an iron sulphate solution, some others with a chelated iron solution and then the third set of trees I wired up some old horseshoes and pipe connections in the center of the trees. Some trees I left alone as controls. That night it got down to 24 or 25 degrees F. A week or 2 later I checked them out and sure enough. All the controls had lost their fruit. But amazingly all the others treated with the junk and any form of iron had fruit. The one that stood out with the most was the one treated with iron sulphate. In fact, almost every bloom had set fruit so that I had to thin them out.
Anyway, I thought I'd share this in case anyone else wants to try it. I'm still curious as to the minimum temp that this will work so please let me know if you decide to give it a try.