I have pruned the plum trees for someone for a number of years and have been discouraged with the realization that the fruit crop is only getting worse and not better. I know plum trees age but still this is a bit much. I confess to having done some of my early pruning years ago during months where the weather was too wet and thus I opened the possibility of these trees getting a bacterial disease and branch dieback. There was indeed some dieback originally but not anymore. Now, the trees are okay, and there are plenty of blossoms, and plenty of little plums that start to develop and then essentially all of the little plums stop growing and just fall to the ground in early June. I added mason bees to the orchard this year and they did not help. Any ideas as to what the problem is? Here are my leading guesses:
(1) Plum trees more than 40 years old in our climate may not do well. I don't know.
(2) There may be a missing nutrient, like Boron or Magnesium, but a soil sample did not show this.
(3) My pruning 8 years ago in wet weather may have permanently ruined the ability to set fruit. Is that possible?
(4) There may have been other plum trees in the neighborhood that allowed for cross-pollination that are no longer present. (I have installed some new young plum trees which should start blooming in 2019 and we shall see).
(5) The trees were once on an irrigation system but have not been irrigated for the past 10 years. I am partially remedying this problem. Could drought stress in July and August permanently weaken the trees?
Thanks for any thoughts.
Don Ricks said
I added mason bees to the orchard this year and they did not help..
...(4) There may have been other plum trees in the neighborhood that allowed for cross-pollination that are no longer present. (I have installed some new young plum trees which should start blooming in 2019 and we shall see).
If your new trees are not hybrid plums and there is proper synchronization of flowers then I think you should be okay. However some plums are selected purposely for the inability to set very much such as 'thundercloud' (red leaves) so they are more tidy around roadway landscapes. If this is the case then grafting on better producing plums will also be required.
My guess is 3 and 4. Luther Burbank cross bred many types of plums from different continents. The problem is that many will not pollinate each other. Some have American, Asian, and European mixed together in the wrong quantities.
I had a Santa Rosa plum that pumped out lots of plums until I pruned it during a storm. It took a lot of work to get it back to health.
JohN S
PDX OR
Is the plum tree still in healthy shape and still in full sun? (or did a forest of taller trees grow up around it and shade it out?)
I planted Euro plums Brooks and Italian trees 15 years ago. This is the first year they have set much fruit while my Asian plum Early Golden and Damson plums have always set fruit. I wonder if the Euro plums are more susceptible to cold weather when blooming and will abort the fruit, they've always set good blossoms. The Asian plum blooms earlier than Brooks and Italian too so the Asians are experiencing colder weather. My trees get about 7 hours of full sun a day (10 - 5) before being shaded by a big cottonwood clump. I have mason bees and lots of bumblebees and honeybees active in the yard.
My guess is ‘4,’ “There may have been other plum trees in the neighborhood that allowed for cross-pollination that are no longer present.” Proper pollination of Asian plums have been a problem for me.
You describe, “...there are plenty of blossoms, and plenty of little plums that start to develop and then essentially all of the little plums stop growing and just fall to the ground in early June.” That’s an indicator to me of a lack of adequate pollination. I’m assuming this is an Asian, not a European plum. The plant breeder Luther Burbank came up with some extremely tasty Asian plums, but his process was basically a lot of inbreeding. Consequently, plums in his line of cultivars are very pollen specific, and it can’t be anything they’re remotely related to. (So I'll agree with John, above, though I wrote this without reading the responses).
If it’s a 40+ year old tree, or you’re concerned about it’s overall health, it should be obvious. Even if a couple limbs are showing signs of decay, the remaining limbs should be producing fruit. If your new plum trees are complementary pollinators, that should do the trick, but as mentioned, genetic compatibility and overlapping bloom times are critical factors with Asian plums.
Dubyadee,
My Asian plums have always fruited way earlier than my Euros. One of my Euro trees wasn't grafted though, so it took longer. Actually neither was grafted. Yes, I also agree, the earlier pollination can affect things.
John S
PDX OR
John S said
Dubyadee,My Asian plums have always fruited way earlier than my Euros. One of my Euro trees wasn't grafted though, so it took longer. Actually neither was grafted. Yes, I also agree, the earlier pollination can affect things.
John S
PDX OR
I have an Elephant Heart, and though it is still quite small, it does flower every year. Fruit doesn't set, and I don't expect it to. These trees blossom very early in the year, purportedly need to be pollinated by another Japanese plum, and even then, it requires that an inordinately early blooming plum...do the pollinating.
At some point, I'll look at that tree, decide it is old enough to go to work, and I'll graft on a pollinator.