Not sure if it's the same, but our local pyo place had a notice up about its cherries, saying that the wet weather meant they'd split open, but that they should still be fine to eat. Guess it's the same for your plums.
<slight snigger at 'your plums' - sorry, I have a mind like a sewer>
oh pants. i have taken the netting off the tree thinkingthey were never going to be worth picking. spose i should wait and see.
lol at plum joke- takes a while to phrase things on here without causing a fnaw fnaw!
we have a plum tree in our garden this happened to us last year and there were no edible plums incidnetally this year it seems to have been just fine, we have had some we cant eat, but lots of plums that have ripened just fine
It's usually getting a sudden drenching of rain that splits fruit - it swells up too quickly inside and the skin splits as it doesn't grow fast enough to keep up. And then the nasties get in and spoil it for good.
It happened to our cherries in July but not the plums this month.
There isn't much you can do to prevent it happening in future years - you can try watering the tree if the weather is dry after the fruit has formed on the tree, so it doesn't 'gorge' itself on water should we get a sudden downpour.
Our plum tree is just groaning with fruit, whhich we have just started picking (gave away about 2 kg to our neigbhour to make plum chutney and made 5.4kg of jam myself - to add to the 4 kg of pear jam I also made this weekend SDtill have loads of fruit to pick).
Only one or two have split (the tree is sheltered by a large pear tree which might have "regulated" the water.
I found this comment from Adam Pasco on the Garder's World Web site, "The fruit's skin grows quite slowly, and if heavy rain causes the plant to take up moisture quickly the fruit swells causing skin to split."