If the trees are short enough, you can tent them with plastic to help hold in the heat. Adding buckets, barrels or molasses feed tubs full of water would help. When I use water like that, I fill up the containers early in the day so they can soak up sunlight and heat up the water somewhat. With water as a solar collector under thick plastic (when I've done this I've used 4 mm or 6 mm plastic), you often can keep the plants warmer than the surrounding air temperature. The plastic needs to go all the way down to the ground to keep the cool air away from the trees. This is pretty effective with young, fairly short and fairly small trees. The larger the trees, the harder it is to protect them, especially in high wind.

I'm not even going to try to protect my plum trees as they've already been exposed to multiple nights in the 20s. With the peach trees, they're so small that I could cover them up, but I won't bother unless the wind really drops this afternoon.

I know people who've put little heaters on the ground underneath trees tented with plastic or light bulbs or heat lamp type light bulbs like you use in a chicken coop in the trees themselves, but there's no guarantees with any of these methods. They also can become fire hazards in some conditions.

As part of growing fruit in OK, I just accept that about 1 year out of 3 either a hard frost or late freeze while or after the trees are blooming will wipe out the crop, and I don't go to extraordinary lengths to protect them. My trees are too old and, therefore, too big to protect unless I come up with a circus tent or something, which isn't likely.

Good luck protecting your trees.

Dawn