It’s kind of a nice mystery but a mystery never the less. This photo is of the plums on my Mariana plum tree. Yes, this is Mariana, normally grown as root stock. I bet there is a many a grafted plum tree out there that isn’t as good as the root stock, in the case of Mariana, if only the root stock was given a chance.
Actually Mariana’s reputation is that as a fruiting tree it bares sparsely with very small but delicious plum. I’m guessing the people who wrote that description has never tried pollinizing Mariana with hog plum, Prunus umbelata? The three times before when Mariana bore fruit, it was apparently pollinized by Green Gage. The crops were always sparse, and the plums were always really small. Last year after Green Gage died, all three of my three adult plum trees bloomed together, but Mariana only made about five very puny plums. I did some research and discovered that our local native P. umbelatta which bloom with Mariana is a super close relative to the Munson parent of Mariana. So I brought a bucket full of P. umbalata flowers in the yard, this is the crop I got rewarded for my efforts with.
It seems clear to me that P. umbelatta as a pollinizer is the reason for the abundance of plums. But here is the mystery. Why are the plums so large? A possible explanation is that I gave the tree some Epson salts to take care of a possible magnesium deficiency in the soil. But I gave all the plum trees Epson salts, and the Toole’s Heirloom plums are unusually small this year. These plums are huge in comparison to what this tree has ever produced before, and it has a least six times the amount of fruit lode on it.
Can a fully compatible pollinizer result in higher quality plums? My intuitive thought is that it would result in more plums, not bigger plums. If having a better pollinizer does result in bigger plums, what’s the mechanism. The fruit has the genetics of the mother tree, not the pollen parent. Besides hog plums are tiny bitter plums. Could it be that the hog plum genes are stimulating the seed embryos to secrete hormones that are causing the ovaries (plums) to grow bigger? The individual plums are at least twice the size of the ones it produced in 2016 and 2015, Mariana is by far my favorite of my plums for fresh eating flavor. I can’t hardly wait to try these beauties. By the way, this a 20 foot tall, 30 foot diameter tree with the whole tree loaded like this. If Mariana can be made to produce like this, why is it just relegated to root stock? God bless.