Uncharted- but there are lots of charts! Thank you Fruitnut for your experience and Ace as well. My J. plums still look absolutely beautiful as the cool weather we're having now is extending the bloom. I shall see this as a hopeful sign. Maybe the charts are precise in terms of the temperature the buds or flowers receive while I only get a reading where the sensor is. Common sense says duration has to be a factor as well. I still haven't pruned a few of my plum trees and will leave them alone until I am sure that all the fruit isn't on the tips of highest branches, which I would otherwise remove. Won't hurt to prune them late anyway- if it slows them a bit it won't matter. I haven't touched my peaches so I guess I'll wait on them as well. The problem with this strategy is that it wasn't really a still convection freeze and there was some breeze stirring things up. I hope to write and read stories of successful harvests in the months ahead from all of us who suffered this round of untimely frost. Good luck.

I'm guessing that the open blooms are done for - whether pollinated or not. We had that happen to our apricots, a couple of years ago, though, and got another small round of blooms on one of the trees a good two weeks later, so don't give up hope yet! Personally, I'd go ahead and spray.since the weather conditions that woke up the trees may have also gotten the insects and fungi started. I think the main thing is to avoid spraying open blossoms that are waiting to be pollinated.

Today. the rains have returned. The crocuses have pulled their petals shut and the plum blossoms are dark with moisture, but the garden is bright with the pink and red flowers of camellias glowing in the murk.

This is a complex situation! Just got through dealing with this last week, and the questions of whether or not to cover, what to cover, and how to cover are part of the annual ritual (unfortunately) for me. A few words of advice: 1. Covering can be a royal pain, especially with large trees in windy weather. It can damage branches unless you create a nice structure around the tree to support the plastic. 2. It rarely causes miracles (i.e. saves all of a crop). More often people think it worked, but the trees would have fruited without any help anyway. 3, Using plastic, NOT some bed sheet or porous "frost blanket", plus a heat source underneath (light bulb, heater, etc…) is essential. 4. Remember that Euro plums can take 23 degrees F during the latter stages of flowering and fruit set and still produce something (albeit 10% of crop), especially if the weather is windy and/or cloudy at the time. 5. Clear plastic should be at least partially removed before sunny weather the next day to avoid overheating (maybe this is just me being cautious in my ultra sunny climate). So, to sum up… if you think it really will get down into the low 20's, covering the right way may save some fruit, but it will take special care and a good bit of work. In many cases it is better to just cross your fingers and hope for the best! In case you're interested, the temp hit 18 degrees at my house one night last week. With three individual trees (dwarfs) covered, and a makeshift 15 foot "hoop house" covering a scattering of closely planted fruit trees, I managed to save the odd blossom of nectarine, sweet cherry, and Euro plum. Anything not covered was completely killed, except for the smallest unopened apple buds. The hoop house did not save anything at all, even though I used an electric space heater inside it, while the smaller more successful covering had only light bulbs for heat. Sorry for the length of this, whew!