Okay, I'm going to float a theory about my poorly performing Crimson Passion bushes, just to see what some of your thoughts are...
A little history is in order to "set the stage"
When I first got the little twigs from HBUSA, within a few days of planting I noticed one of them had a touch of gummosis. At that point the only bush cherries I had were the 5 CJ's and they were all healthy as horses - nothing bad going on with any of them to speak of (Although I did think one had some signs of BC, but that never turned out to be much).
So my thinking was that they arrived here with some kind of issue. When I spoke with HBUSA about it, they said the CP's were a bit more "finicky", and that some of their young CP plants had some issues but that they seem to generally outgrow these problems and that I could spray them with copper and I should be okay.
Well to add insult to injury, on 9/7/14 I'd removed the fencing to weed and came inside to eat - nodded off and completely forgot about it. Next morning I was drinking coffee and noticed some deer messing around by the bush and sure enough they had defoliated the one, and quite a bit of the other. I didn't know how it'd survive the winter but it seemed to do fine.
2015 came and went kind of nothing out of the ordinary, the CP's grew at a nice clip and overall I was pleased with how they were doing.
2016 rolls around and the CP's looked green and lush and I thought for all the world that I'd get to taste fruit - but alas..., not a single blossom. THEN (and here's where the theory comes in....) late July/early August these two CP's got hit with the dreaded cherry leaf spot. None of the 5 CJ's next to the CP's had any cherry leaf spot, nor did the newly planted but very nicely leafed out 2 Juliet bushes have any. Only CP. (I recall in a thread Clark had said maybe JB's deposited there, but that his CJ's had been hit)
In any case, these CP's lost a lot of leaves as I was a bit tardy in hitting them once I noticed the outbreak.
Then they come out of winter this spring looking like winter-kill, and on closer inspection I see tiny leaves but nothing to power them and the bushes look sparse as a result. There was some winter-kill, but a lot of just under performing branches.
I hit 'em hard with extra fert, and now I have some new growth that's maybe 10". However, I've noticed that some of them are weak at the union and often I walk past and see three or four new 10" branches wilted and drooping. They just fall off the main branch. I also noticed about 20-40 leaves with leaf spot that appeared seemingly overnight. I hit them with Immunox today, but thing is I've hit them with Kocide 3000 and Immunox right along with my others all along from winter to spring whenever the others are sprayed.
So anyway, I think one of the MSU articles eludes to cherry trees suffering the next year after having had severe cherry leaf spot.
Well I'm thinking if I keep pampering these two - maybe it's just the leaf spot that is my issue and once they're more healthy BOOM! (and yet I can't escape the other seemingly universal evidence that these CP's are just not very good producers).
Anyway, just a ramble......