Jean wrote, For hardy plants, the damage occurs at 32F or below. And as has been >noted in earlier posts, it often occurs somewhat below 32. The reason: >plant cells contain various components which act as a sort of >anti-freeze. One curious observation about "anti-freeze": I have a lot of deciduous magnolias, and some of them have flowers that are destroyed by freezing, while others (e.g., M. x loebneri hybrids such as 'Ballerina') seem to have anti-freeze in the flowers. I think the same can be observed among rhododendrons. Jane McGary