Andrew,
I thought Ruby Queen is another one of those hybrids (some are stinger than the others).
In your situation, it could be that the timing of their blooms are not quite match and that your trees are still young. By next year, you’ll be complaining that your trees set too many fruit!!!
I have Satsuma, Ruby Queen, Early Golden, and Nadia.
We had almost ideal weather this year with an extended relatively warm, dry, sunny period while they were all in bloom.
Early Golden set a tremendous crop of fruit, Satsuma has set some, Nadia has set only a few (and it didn’t flower all that profusely). I need to check how much fruit Ruby Queen set.
I have yet to have a satsuma set despite it being one of my best bloomers. This year that might have changed.
Hi All,
My Beauty Plum has set a lot of fruits. Most of them are 3/4 ~ 1 inch size now. Is it still a good idea to thin them (is it too late)? I’ve never thinned the plums on this tree before.
I’d thin them,at least for the reason of stopping the branch from breaking.bb
I would thin them so they are not touching when ripe. Just my 2 cents.
Thank you Bradybb and nil!
I will thin them out today.
Satsuma takes awhile to get setting but once it starts it is soon too much. I have thinned hundreds already and have many hundreds more to go. Shiro, Early Blush, and Lavina are also over-setters for me. Laroda, Dapple Dandy, Weeping Santa Rosa are “just right”, they don’t set all that many and thinning is not much work at all. The more trees you get the more you appreciate ones that set just right… thinning on a large tree can take a lot of time. My Rubinette apple took me 20 minutes or more already and it still is only half thinned.
@NoVA, my Early Blush looks like that right now which is after thinning 2/3rds of the plums. I need to thin some more…
Satsuma sets so much so we call it the satsuma cherry now. 
It’s a dog to depit when making jam. For us it has to be thinned 8 out of ten on the sunny branches to get a decent size. Interestingly the shaded branches set a lot less and also ripen much later.
Unbelievable how many plums these trees can set. I start to think probably I have planted too many this year. I planted 6 plums this year. It may not sound many, but I had very strict quota of two for all other trees. 
I had to give up the idea of adding two peach trees.
I have grown Satsuma for about 8 years now. It has never produced well for me at all. The major issue is that it gets only 4-5 hours of sun. That makes it unproductive.
Another issue is the flower buds are not very cold hardy, not in my location, zone 6 a. A few years ago, buds were killed by freeze. Last year, incessant rain ruined pollination. This year, it looked like late freeze killed blooms.
A few years that it set fruit, I like it though fruit is on a small size. Now that I have Elephant Heart that is 3 x the size and tastes as good or even better. I would have remove Satsuma had I not grafted quite a few varieties on it.
I have a satsuma tree that has set basically zero fruit before this year. This year it set a crop but not nearly enough that I would think about thinning it. Hopefully now that it is going it will ramp up. I think this is its 5th year and it is in a great sunny location.
I don’t think Shiro is that great for eating either. I like that it’s relatively trouble free, grows a nice shape, and seems reliable.
Last fall I juiced it in the steam juicer, added some sugar to bring up the brix, and quite enjoyed it. Especially the bottles pulled from the freezer in the winter.
I grow Satsuma here and it’s a favorite J. plum. Reliability is average, but when it crops it needs thinning and probably sets fruit 2 of 3 years. My first tree died from some kind of cambium freeze and the tree tends to suffer that kind of damage so I suppose we are a tad too cold for optimum performance and longevity here. Santa Rosa and Elephant Heart also sometimes are damaged this way.
Reema is a new one for me and the previous 3 years has born fruit on good and bad years, although nothing is bearing this terrible one. Reema seems an excellent NE variety so far.
Now Shiro bears fruit I seldom eat although sometimes young trees without extensive roots in my nursery produce sweet enough fruit to be very good. My 25 year old tree just has too extensive a root system not to produce rather bland fruit most years, although guests still love it. In my nursery I’m using it as a mother tree to put one or two other varieties onto, much as I use Blue Byrd for my E plums, although I’m having second thoughts about BB. It lacks the vigor I need, even on myro.
If Shiro is prolific but bland maybe it might pair well with currents which some people find to strongly flavored.
