Considering that all of my other fruit trees are blooming right now, my Blenheim Apricot should be in full bloom right now. It has sparse flowers on it. Whatever buds I touch gently, crumble in my hands and they are green inside. What’s going on? 
My neighbor’s apricot tree is doing the same thing. We got a few nights in the 30s last week and some frost on the ground. But nowhere near freezing!
My Goldkist went into full bloom (always the first tree of mine) but my blenheim only has a few flowers. I should go check the buds after reading your post.
“Frost” occurs by sublimation – the white dust you see is frozen water vapor. It is a surface phenomenon caused by (reverse) heat flow.
I think you’ve got it backwards Prof. Richard. Sublimation is the change of phase from solid directly to gas. The opposite ( Gas to Solid) is deposition.
Source:
That’s unfortunate. I had similar conditions as you for a couple nights last week (~34F) – but the blooms on Gold Kist look fine. Half the blooms are still unopened so I’m not so concerned.
I’ve had this issue in my greenhouse every yr. It never freezes in there. It also occurs on pluots. The worst for me is Orangered apricot followed by Robada, my two best tasting apricots. Sweet cherries have what I think is another manifestation of the same issue. The buds don’t abort but the flowers aren’t properly developed. They lack pollen and may have several ovaries. The self fertile cherries have more issues than Bing or Rainier.
On pluots it usually isn’t bad enough to reduce yield. It can reduce yield of apricots and cherries by 90% or more.
I don’t know what’s going on. I’ve tried a number of things in hopes of over coming the issue. I don’t think it’s lack of chilling. I’ve run up to 1350 Utah chill hrs with no improvement. I’ve doubled my usual stingy water level, no help. This yr I warmed the greenhouse back up more slowly after finishing chilling and reduced the diurnal temperature swings. Robada is a lot better than last yr so I may pursue that more next yr.
I haven’t solved this and probably never will. I’ve worked on it too many yrs with little results. It may be related to the very long growing season in my greenhouse and in Socal. But we can’t shorten that. It may be that winter is too short irregardless of chilling hrs. I’m still just guessing.
I have a number of grafts on the tree. Tomcot set lots of blossoms but zero set probably because of the heavy rains we got at the same time. Afghanistan, Moorpark, Orangered, Blenheim all are lacking blooms.
Thanks!
@fruitnut, you are so thorough about things that I’m guessing you have checked many times that the trees in question have enough available potash going into the Fall.(?)
Well, @bleedingdirt is not in SoCal. However, I am … and I’ve seen apricots have this problem, especially in near coastal areas. Down in Point Loma there is a Blenheim known to local fruit enthusiasts (on D. Ross’s old property) that when planted decades ago did not set much if any fruit. For nutrients it received no more than yearly mulch and manures. Fourteen years later it woke up and started producing. In my experience I’ve seen plenty of Katy apricots do this in recent decades under the same circumstances, although the acclimatization process only took 4-5 years. I’m currently growing one at my present location in Vista (10b) and expect a couple dozen fruits this year.
@fruitnut and I discussed this phenomenon last year. Apparently, it’s just what apricots do. Mine did it last year and I still got a pretty decent harvest.
This year, my Gold Kist bloomed through the heavy rains, so I’m not expecting many fruits on it, but I’m planning to top-work most of its branches with other varieties anyway. Tomcot and Nicole opened most of their flowers after the rains ended, so I hope they will do ok. Autumn Glo started blooming a few days ago. Tilton, Orangered, Moorpark, Afghanistan and Harcot did not start blooming yet. Overall, apricot bloom seems to be less profuse and more prolonged this year.
I had two soil tests done by Texas A&M labs this past winter. Soil nutrient levels in ppm were as follows
P 53 ppm vs 50 ppm critical level
K 413 ppm vs 160
Ca 4400 ppm vs 180
Mg 361 ppm vs 50
S 30 ppm vs 13
Iron 5.9 ppm vs 4.2
Zn 4.2 ppm vs 0.3
Mn 15 ppm vs 1.0
Cu 0.55 ppm vs 0.16
Very high in K so I don’t see how that can be the issue.
The soil is very high in Zn and Mn. High enough to have me concerned. I didn’t apply that I think the guy before me put it on his pecan trees that occupied the space that is now greenhouse.
The fact that apricots have the same issue in CA as in my greenhouse does help me rule out one factor that I’ve thought about. That would be light intensity and quality which are different in my greenhouse than outdoors.
We do have some of this issue outdoors here. But both apricots and sweet cherries bloom and set better outdoors than in the greenhouse. Unfortunately they get frozen outdoors or eaten by birds.
So I need to concentrate on correcting what’s different outside vs in. I’d say my chilling system is so good in the greenhouse that I get more chilling in than out. Water and soil are similar. That takes me back to the length of dormancy. That’s probably a month or two longer outdoors. And outdoors there is the freezing weather at times. That isn’t supposed to provide chilling but maybe something is going on there.
Way to go on the phosphate level … quite an admirable place to be given the Ca concentration.
At this time of the year I’m ok with the K concentration, although 450 ppm would be a point of concern and I’d like to see it drop below 200 before re-application.
Nut growers often apply Zn in a foliar compound to enhance crop weight. Your Zn level would be a bit high but reasonable in disease-prone crops, esp. grapes. Also, as an electrolyte Zn is second only to Cu for plants and so uptake is inevitable provided you continue with your controlled approach to inputs.
As you point out, the Mn concentration is of concern. However, if nitrogen-driven growth seems normal then apparently your Sulfur level is keeping it (and the Ca) in check. Uptake of Mn is slow but essential so it too could dissipate over time.
Yes, our winters in CA are pretty short, usually the chill accumulation period lasts about two months (Dec and Jan), although this year it was closer to three months.
That’s the native level in these desert soils. I haven’t applied any and never would.
My chill accumulation period this yr was only about 45 days. I can average 18 Utah hrs per day. I’ve gone 75 days in the past with no change in bud abortion. Usually 60 days which I’ll do next yr. I might ought to take longer going into and out of that period, ie cooler Oct, and Jan-March.
Reason I like a long season is I’m going more and more into figs. They’d like 11 months of 90+F. Cool weather shortens my harvest season a month or two on figs. So everything is a compromise.
In a sick, twisted way, I’m glad I’m not the only one! But I’m bummed there is no cause identified let alone resolution 
I feel the same way and this does help me. I’ve got a feeling it’s just that our winter is too short for apricots and apricot related fruits. Sweet cherries are another crop native to areas with long cool to cold winters. The sweet cherry blossoms don’t develop properly probably because there just isn’t time enough for that to occur.
I’ve had zero issues on nectarines and peaches, inside or out. They always bloom well even fairly high chill stuff. The really low chill stuff blooms in January even outside.
I guess I need two different greenhouses. One for figs and low chill nectarines with about 11 warm months and another with the longest winter I could provide.
I thought I lived in Apricot country! At this point, I suspect the causes are heavy rains and/or wild temperature swings during bloom time.
Heavy rains can be an issue but not likely unless it leads to shuck rot or another disease. Excessive diurnal temperature spread has been a possible cause in my mind. This yr during the first month after chilling. January,I held the greenhouse to about 66/42F nearly every day. I’m not sure that helped any vs former yrs where it was more like 80/34F.
As to wild temperature swings nowhere in the country is worse than here all winter long. My greenhouse is very stable by comparison. Most days are sunny and I have to cool by day and heat at night in winter. Yet apricots bloom better outdoors than inside. It’s not wild temperature swings.
