Based on the link below, it looks like your white tipped plums can handle temperatures down to 17 F before there is any damage. Look at the link. Based on your description, it sounds like the buds are at Stage 2.

Here is a link that might be useful: Fruit Bud Hardiness

If the temperature were just right, consistently in the 30s, the trees could be held off several months. The nurseries are doing that right now to hold their bare root trees until shipment. But with the vagaries of weather outdoors you will be very lucky if your early bloomers hold off thru March.

We got a warm spell in January and have apricots starting to bloom outdoors now.

This post was edited by fruitnut on Thu, Feb 28, 13 at 11:21

dmtaylor, great link!

One of my peach trees is also budding out, and has a couple of open flowers. I've been pretty concerned with the cold temps coming this weekend- dipping into the mid 20s. I'll cover it, but even without protection it looks like most of the buds should be ok.

We still have projected temps into the 30's abd 40's for the next two weeks. My apple buds are showing red, and my peach buds are swelling. The weather has been so bad I have not yet been able to prune, or spray, due to all of the snow and rain. Spring? My snow drops are up but this is the first year in about six years I have not had crocus out by the end of Feb. Global warming didn't hit this winter in RI. Mrs. G

Oddly our winter did not kick in until several weeks ago
our 1st nights below freezing began in Feb
Almonds & of course Pluots were swollen bud stage
but stopped cold, seem fine just waiting for warm weather
Peach & Apricots still dormant guess its the cultivar

Thanks for all the interesting thoughts. I'm wondering especially about the scenario Fruitnut and GreenOrchard described where it was warm in January and that got some things started like Fruitnut's apricots and GreenOrchard's almonds and pluots. In other words, I know things can stay dormant a long time if it stays cold, but what about once they've broken dormancy? To what degree can trees break dormancy, progress toward flowering, and then go back into a kind of dormancy? Or once they've broken dormancy will they proceed to flower even if it's colder than would have brought them out of dormancy in the first place? I'm sure there isn't any easy, straightforward answer, but I'd be interested in your observations. It sounds like Fruitnut's apricots continued toward flowering but GreenOrchard's almonds just stopped progressing. Thanks.