I've never seen critical temps for Japanese plums posted as there are for a number of other fruits on the MSU site and the like and have based my assessment for any need for protection against freeze injury on the European plum data.This year my orchard was exposed for several hours to 24 -25F before buds had reached tight cluster and I thought most all was safe, but I'm now seeing 90 - 100% loss on the earlier blooming Japanese varieties. The European plums are unaffected.Now there are other reasons for poor fruit set here, but this seems the most likely, and in the future I will regard even moderately freezing temps (Can any others report significant losses at these moderately freezing temps for early stage Japanese plum buds?