I know that insufficient chill hours, insufficient pollination, and/or insufficient tree age/maturity can each cause non-bearing, but I’d like to understand the mechanism of each. In other words; what, specifically, does insufficient chill hours, for example, do to cause non-bearing? Does it prevent bloom, or does it allow a good bloom but inhibit fertilization, or cause fruit drop? How does a tree being too young cause non-fruiting? Does it throw off bloom timing, indirectly interfering with pollination. How do each of these three problems work?
I want to understand in general, but I also want to diagnose why my Elephant Heart Plum, planted three and a half years ago, has never fruited. Does the fact that it had many blooms this year indicate sufficient chill, or does insufficient chill work via some other mechanism?
My EH plum bloomed well, but later than my other two plum trees (Santa Rosa and Satsuma) with little overlap, but there were a few blossoms still on my Santa Rosa plum.
In short: for an Elephant Heart Plum that bloomed but developed no fruit, what are the symptoms of:
Insufficient chill (no bloom, early/late bloom, blocked pollination, fruit drop ???)
Insufficient tree maturity (no bloom, early/late bloom, blocked pollination, fruit drop ???)
Absence of an appropriate pollinator (early/late bloom, fruit drop ???)
Thanks
PS I also have about six pluots, can they pollinate a plum? none bloomed as late as the EH plum though.
A tree that’s too young simply doesn’t flower. My young trees that flower set fruit. The lone exception would be the yr of planting. Even some of those set but many don’t.
Your 3.5 yr EH that bloomed well certainly isn’t too young to set. That sounds like it wasn’t pollinated. Either a lack of bees or a lack of nearby suitable pollen source. Bloom might be delayed due to insufficient chilling.
Pluots can pollinate a plum and vise versa. They probably don’t all work but enough do with the numbers you have you’ll be OK.
I note you are Z9-10. Short winter areas can have issues with flower bud abortion as the buds swell in spring. The worst for this is apricots less so pluots. There can also be issues with flowers that don’t develop properly, mostly sweet cherries.
Insufficent chilling affects the foliage as much or more than flower buds. If the foliage emergence and bloom are delayed that could be lack of chilling. So that could be an issue with your EH. But if it bloomed late it still might set. I really haven’t had much experience with insufficient chilling. But lots with winter too short.
Thanks Fruitnut!
From what you’ve written, and what I’ve read elsewhere, low chill can result in late foliage emergence (branch tips only at first) and late bloom. I didn’t know to watch for late foliage emergence, but according to the data from the weather station in my orchard, I only got about 265 chill hours this winter (unusually mild). I got another 100 hours just slightly warmer than 45 degrees (45.01-46.99) which probably means that 315-350 is a more realistic estimate of my chill hours. Either way, probably not enough for my Elephant Heart which is listed as needing “500 chill hours or less”.
It sounds like my EH plum didn’t get cross-pollinated, because of its late bloom relative to my Santa Rosa plum, and my pluots. The lower than 500 chill hours may have caused the late bloom, and missed the window for pollination. On the other hand, maybe I’m at risk of missing that window even if I get more chll hours. The Dave Wilson site says “Pollenize [EH] with Beauty or Santa Rosa”, but it lists the EH plum as blooming “Late” and the SR plum as blooming “Mid-season”.
The DW website says that Beauty plum is also a “Late” bloomer. I wonder if Beauty might be a more appropriate pollinator for my Elephant Heart plum than Santa Rosa, for my climate. I’ve read speculation that a long blooming season (early/long spring) like I have here (inland valley 15 miles East of San Diego) might allow blooms to miss each other that reliably overlap in colder areas where spring comes more distinctly.
I have one spot left in my orchard, that I was hoping to put a fig in, but maybe I need a beauty plum there instead, to pollinate my Elephant Heart plum.
Maybe this is a question for another thread, but do you think it would be sufficient for pollination to simply graft a branch of a Beauty plum onto my Elephant Heart plum tree (or an adjacent tree), assuming that my Santa Rosa isn’t going to get the job done?
Yes grafting could help. Emerald Beaut is a late blooming plum but is listed at 6-700 hrs. I don’t know what else to recommend. Beauty isn’t a real good fruit IME. I prefer Burgundy.
Beauty plum was an early bloomer for me. It has an extended bloom period but it is not a late bloomer. It does set a lot of fruits. Flavor Grenade I think is a late bloomer and it sets fruits really easy, comparatively to the other plums.
From your description it seems like the lack of pollination might be a problem. Grafting another variety or two on the tree should help. Low-chill plums that should be decent pollinators for EH are Methley, Beauty, Burgundy, Howard Miracle, Golden Nectar.
I am in 9B and the last 2 years had lower than normal chill hours(average about 550 hours) I have had a hard time getting my plums to produce except for Gulf Beauty and Gulf Rose, very low chill hours. The other plums, golden nectar, mariposa, and methley will produce a few blooms but they do not set. They are about 4 years old and good sized trees. My La Feliciana peach trees have produced blooms but nearly all fall off. They produced very well 3 years ago when I had more chill hours.
I am wondering if the higher chill hour plums will produce in my environment except on years with above average chill hours. I will give the plums one more year. I also have a white delight #2 peach that produced well last year but after blooming well this year, they all fell off. It has a chill requirement of 500. My artic star nectarine blooms well, but only producers about 6 fruits. It is only 3 years old but is a very vigorous tree. My snow queen nectarine blooms less and last year only produced a couple of fruit. This year it is having a hard time breaking dormancy.
My tropic snow peaches bloom well and set enough fruit that I have to thin. I think with my humid warm winter I may not be getting as many effective chill hours as other people. In other words, even though the weather station shows 400 chill hours, I may only have 2/3 that amount the due to the warm humid temperatures causing the tree to lose chill hours.
Whatever happened with your elephant heart plum? Did adding late pollinators help? Did it need just a few years to bear? Or is it something that just doesn’t produce much in San Diego?
I had a similar situation to you with a color sport of elephant heart, broken heart. Wonderful flavor but not as productive.