@ztom… my two jplum trees are AU Rosa and Shiro.
This was year 2 in ground here for them.
Last spring I added a graft of AU Producer to my AU Rosa.
This spring after a year in ground AU Rosa opened first blooms March 1.
My graft of AU Producer and my Shiro tree started blooming 4 or 5 days later. AU Rosa was still blooming some when they started.
AU Rosa is self fertile and will set heavy loads of fruit with no other pollinator… it did that last spring.
But now my later AU Rosa blossoms have AU Producer and Shiro to pollinate with.
This spring I added grafts (looking successful) of Beauty (a late bloomer) Spring Satin plumcot, South Mtn EB plumcot, Alderman, Superior, Vic Red american plum.
I am hoping that the late bloomer Alderman… will bloom with either Beauty or Vic Red.
Hopefully get to find out next spring.
My Jplums almost always bloom and set fruit (early to mid March)… then get frosted (mid to upper 20s) and drop fruit.
Happened last year and again this year… last year dropped all fruit this year dropped most… retaining a small amount.
I need later bloomers to hopefully get me past that problem in some years.
I tried to find out for sure which other jplums or hybrids or americans bloom with alderman… but never got a positive ID on that.
Waneta is a possible suspect.
Right now my EU Plum Mt Royal is giving me the most plum crop hope. It starts blooming 3 weeks after AU Rosa… and is in full bloom right now first week in April.
In some years we get mid to upper 20s in early to mid April.
Hope this year is nicer than that.