greatest unanswered mysteries of fruit trees

alan haighJune 15, 2012

I think it's been a bit dull here lately so maybe this will liven things up a bit. Let's hear your observations of strange and mysterious fruit tree behavior, things that you have no logical explanation for, and see if anyone else can diagnose or at least theorize what's going on. I'll start with this...

Uneven fruitset- Why do some trees set all their fruit on just a couple of branches where the fruit is all clustered up and the entire remainder of the tree is barren? I've often seen this happen with apples and European plums.

A similar question I put out last year was about same variety trees (Damson plums) a few feet from each other that had born similarly the previous season but in the current season one tree was barren while the other was loaded with fruit. Never got what I considered a very satisfactory theory for that one.

I welcome answers and new questions.

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Hello harvestman,

Fruit trees are funny critters. I notice in my fig orchard that the trees under stress, and especially if pruned, give the best and sweetest fruit. Untrimmed, well tended trees give few figs.

I am told that the trees which give edible fruit are female. But just like with humans, if a tree is tall and beautiful and loved, it will want to just make itself taller and ever more attractive, scorning reproduction. But when there is no hope for height and beauty, female, er, female fig trees go for baby production. Making figs abundantly. The Angelina type put all their energy into their looks, the Ma Kettle types go for large broods. Um, we're talking figs here, right?

So, to get a tall, attractive tree to bear fruit, you might want to lower its ambitions, so to speak. Lop off the top of the tree and prune it all around. Make it ugly on purpose! Next season, you might well have a great crop from a sad looking tree.

Hey, it works for figs. And to keep you household small and manageable, keep the wife looking good! When she feels unattractive and unloved, prepare yourself for a new baby.

Universal phenomenon!

    Bookmark   June 15, 2012 at 10:21PM
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franktank232(z5 WI)

I found an apple (one of the over 100 that have fallen) and it had OVER 15 plum curculio egg laying scars. The amount of PC damage this year was the worst ever... I pick up all my fallen fruit off the ground and this year i've filled up bags (peaches, plums, apples)... Next year its more spray... I don't know anymore. I thought I was good, but it just escalated out of control in the second half of May...

Sweet cherries were awesome. By far the best ever and quickly becoming one of my favorite fruits to grow...early, juicy, sweet and somewhat less pest pressure.

I think i'm sick of apricots and I've only ate 3 or 4 of them. I really am not sure why I have so many trees (5 different types). I may need to consolidate all varieties to 1 tree and either remove or graft over the others (probably to plums/peaches).

My pears have mite and aphid issues... They have been horrible this year on some trees.

    Bookmark   June 15, 2012 at 10:41PM
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franktank232(z5 WI)

At least in my yard, fruit set on everything, outside the Hunza apricot and the Black Gold sweet cherry was excellent...amazing considering the 26F temps that visited us, along with several frost events. Its just the curculio was late (for how warm/long the spring was here) having figured curculio would have been done by mid May or so...

    Bookmark   June 15, 2012 at 10:44PM
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Same for me, frank. PCs totally wiped out my Asian plums. I've found multiple larvae in most of the fruit I cut open. This, after multiple sprays of triazicide starting at petal fall. There were no PCs around, then.

The Degree Day chart says they should have been gone a month ago, but just today, picking up infested plums, I found a live weevil, working on the already-ruined fruits.

But here's the mystery - it's only plums. Cots, almost untouched. Cherries, just about perfect. Plums, total ruination.

    Bookmark   June 15, 2012 at 11:52PM
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Well, since this is 'unsolved mysteries' my question is why is that little patch of dirt on the east side of the back porch so much better than anything else? My house is built on undeveloped range land, on a slight slope. Its not very fertile. To the extent there was grading, the topsoil by that fence would probably have been graded off more than the rest of the yard. But everything in that area grows like a Kudzu vine. The North side of the house is almost unusable. Two apricot trees exactly the same variety and rootstock--front house is three and a half feet tall. Back porch tree is maybe 12 feet and has already grown three times more than any tree in the garden--and its a year younger than the tree in front.

Also: Bought some apple rootstock in a pathetic effort to learn to graft. B.9 and Antonovka do well-- M-111 can barely survive. The whole idea of rootstock is that its generally adaptable. Why the difference?

    Bookmark   June 16, 2012 at 12:31AM
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This is not the greatest unanswered mystery. Two of my liberty apple trees have a branch each that sprouted lots of apples on branches that I didn't see any spurs on.

    Bookmark   June 16, 2012 at 7:57AM
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alan haigh

Koko, at least I can provide a theory to the patch. Perhaps there is a difference in soil depth or profile in that spot- have you dug down about 4' in a few places for comparison?

As far as the PC issue, it was anticipated by the spurts that PC would be late this year around here at least. It seems plums are most vulnerable after fruit gets to a certain size- perhaps larger, faster growing fruit just crushes the beasts without any damage once they get to a certain size.

I was hit by late PC on E. plums as well- at least I think that's what it is. Haven't found a single worm and damage has been varied with some large translucent areas instead of just the usual small brown tunneling leading around the pit. On one site J plums as well. I always thin E. plums conservatively because of this issue but at some sites may have to add an additional spray.

BudBE, I enjoyed your prose, but the question is why would individual branches behave completely differently in the same tree? These are trees that have born well in the past and I've not altered my management.

    Bookmark   June 16, 2012 at 8:06AM
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Bradybb WA-Zone8

When watching bees,especially Bumblebees gathering pollen,I wonder how and why they select which flower to land on.A lot of times they very quickly,sometimes in split seconds,make the decision to stay or reject.It may be some other bee's scent placed on the flower? Brady

    Bookmark   June 16, 2012 at 9:49AM
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For me a great mystery is how chill hours work in Texas stop and start winters. I never have been able to fully figure it out. Some years I'm sure nothing is gonna bloom and then we end up getting a great bloom on things and other years I think we will get record blooms and still get scattered and erratic flowering. I dont think there is a real good method to tabulate chill for us here in Texas.


    Bookmark   June 16, 2012 at 10:39AM
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alan haigh

And how would you even know how to separate chill from other issues?

    Bookmark   June 16, 2012 at 10:45AM
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A great mystery of mine is pollination. I have selected many self pollinating fruits trees because I live in the Northeast. What is a mystery is when my Montmorency cherry bloomed its heart our this spring and was covered with hundreds of white blossoms. There must be maybe twenty cherries on the tree (all turned prematurely yellow and dropped). Warm winter, warm spring (except for two nights of 28 degrees in April). A few bumble bees and two bees of another sort. I cannot rely on bees for any pollination until more of my trees are older and they have more blossoms to attract bees. It is amazing that two nights of low temps. can change the direction of a bud that has not even flowered (that is a mystery). My other mystery is a five year old Jonagold covered with fruiting spurs, and only six apples set this spring on end blossoms. Not one spur flowered. I don't know if these are mysteries or frustrations.

    Bookmark   June 16, 2012 at 11:34AM
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Kippy(SoCal zone 10. Sunset Zone 24)

My thoughts.....

I have no plans on ever buying a plum tree to plant. I love plums, so I plan on buying peaches and grafting a branch or two on each to plums.


Cause I have spent sooo much time digging out dog gone blasted plum tree root runners that created bad trees everywhere to create a veggie garden. And even chopped down to the ground the few tiny bits left want to sprout! Worse than digging out a GIANT yucca-not one of those bits has sprouted roots yet. And worse than fig trees-another thing I would never plant unless in a root proof container.

The peach trees co-operate when I have to dig them out! And my plum grafts took easy this year-my first try

    Bookmark   June 16, 2012 at 1:01PM
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alan haigh

Mrs. G, fruit set is about more than pollination, I think. Well bee tended apples of certain varieties didn't set well around here this season probably because we had a warm early spring in late winter then things got back to more "normal" cool temps and lots of gray skies for about a month.

The trees had expended all their reserves growing flowers, foliage and new wood at an accelerated pace and suddenly the rug was pulled under them. In this situation I believe seed production is often aborted as the tree draws back. Leaves couldn't generate enough energy in the cool weather to supply everything and flowers and fruit got jettisoned first.

This is just a theory, however, but I'm almost certain trees don't always hold onto pollinated flowers. My latest flowering apples, which weren't fooled by early spring set quite well- they are the only ones with a decent crop.

Some years timing probably benefits early varieties and some years later ones.

    Bookmark   June 16, 2012 at 4:01PM
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So despite a couple sprays, the bugs and squirrels are getting all my apples and peaches. Yet a half mile away, in an abandoned lot with lots of shade, I can pick great apples and peaches, they seem ignored by the critters and bugs. Go figure.

    Bookmark   June 16, 2012 at 4:41PM
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Thank you H-man, that does make sense. Nature is such a participant in this trying but fascinating world of orchards, large or small.

    Bookmark   June 16, 2012 at 5:08PM
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Scott F Smith(6B/7A MD)

hman, Re: your patchy fruiting, I always viewed that as a variation on alternate bearing. Basically part of the tree got too worn out the previous year (or in general - not enough sun, wrong amount of proper kinds of wood to fruit, etc). Apples and Euro plums are prone to alternate and Jap plums and peaches are not, and that fits with the spotty bearing trends I have seen.

I always have lots of my own mysteries. Like why is pawpaw wood so brittle? My trees keep getting big parts knocked off them.

Why are apricots I grafted on one peach root this spring all red-leaved and not growing well? I assume its a graft incompatibility of some kind but why did all the other peach stocks work fine?

Why are my nectarines so small? I have a few new varieties this year that are huge (Le Grand, now that name makes sense!), but most are just quarter-sized now and don't grow much. I had thought it was peach scab but this year I eliminated most of the scab and still have runts. Well there is still time for them to size up a bit. Along with the smallness the curc was much worse in them so I won't get many fruits.

How can these green plum aphids I have breed so fast? You turn around and a leaf is covered with several layers of them. I have a huge colony of ladybugs this summer keeping up with those guys.

How do the squirrels all know to stay away until my first plums ripen, and then to invite the whole neighborhood over?

How to the deer seem to know when I am out of town, and then munch my new grafts to stubs?


    Bookmark   June 16, 2012 at 5:50PM
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alan haigh

Scott, I will flag fruit loaded branches and see what they do next season. Maybe I will find a trend (no fruit on this years loaded branches) and prove your theory. It sure makes sense. J.plums also do it a lot here- at least Methely, and I think it does it without any such pattern as you suggest.

I think deer kindof case a place like thieves. When normal noises of human activity subside they feel safe. Leave an open window with a talk radio station playing when leaving town. Then they'll only come at night whether you are there or not.

    Bookmark   June 16, 2012 at 6:06PM
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Randy31513(Georgia 8b)

Why is it we can not go to the store like everyone else and buy the crummy fruit they sell?

    Bookmark   June 16, 2012 at 8:29PM
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alan haigh

It's the little balls that keep getting bigger. So addicting, those little growing balls.

OK, that's weird, but I do keep watching these expanding balls and my anticipation just grows with them. Peach balls, apple balls, apricot balls, plum balls, I can't wait for them to transform into sweet, juicy, colorful, balls but it's the waiting and the uncertainty that makes it addicting.

    Bookmark   June 16, 2012 at 8:47PM
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My mystery: What is the biological factor that explains why critters are so damn much smarter than me and maybe you?

I swear if given the chance I'd take 'em at Texas Hold 'Em (no limit now).

    Bookmark   June 16, 2012 at 9:58PM
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I know this mystery has been bugging several other people here. Why does a mature healthy cherry tree that's proved it can fruit when it wants to, that flowers well, that has other cherries for pollenization and bees on the job - fail to yield a single fruit?

    Bookmark   June 16, 2012 at 10:34PM
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swvirginiadave(z6 VA)

I have three Tam Kam Asian persimmon trees all on seedling American rootstock. Trees two and three I grafted from tree one. Tree two is in partial shade; the others in full sun. All three are within 50 yards of each other. Tree one breaks dormancy two weeks before tree two and at least three weeks before tree three. As a result trees two and three escaped major freeze damage this year but tree one did not. It seems that the rootstock (all American) must make the difference but why?

    Bookmark   June 16, 2012 at 11:52PM
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alan haigh

I've never had a problem with cherries but I usually use self-fertile types on Geisla root stocks. Are these fruitless cherries of this genre? I know cross pollination is complicated with cherries and there's a lot of incompatability between different varieties.

They do take a very long time to mature, especially without the use of certain chemicals the commercial growers use to get them to grow fruit spurs instead of vegetative wood. This is especially a problem with traditional root stocks.

    Bookmark   June 17, 2012 at 6:48AM
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My problem cherry is a Stella, self-fertile, on what I suspect is a standard rootstock, though it was sold as "semi-dwarf," a term I have since distrusted. I keep cutting it back so I could reach the cherries if there were any, otherwise it would be immensely tall by now, at around 15 years.

But I keep seeing posts from other people on this forum who seem to have the same problem with some cherry trees, not others.

    Bookmark   June 17, 2012 at 10:06AM
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There is no question that the fascination of growing fruit is addictive. Watching the miracle/mystery of the fruit taking shape is incredible. You can look through catalogues, walk through others orchards, but you can walk around your own tree five times a day and not get bored. I only have fourteen trees, but I am in awe to see real peaches, plums and apples growing before my eyes. THEN, you get to eat them and you are immediately convinced there has never been a better apple, plum, pear, cherry or berry, than YOU have grown. It is amazing.

    Bookmark   June 17, 2012 at 10:14AM
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alan haigh

Hilton, try controlling cherry tree size by pinch pruning during summer, which I believe won't inspire the vegetative response, and if you do it maybe 3 times during the season to short pieces they should become spurs.

After pinching the tip of a scaffold branch several shoots of equal vigor result. Choose one to continue the branch and let it grow till you need more secondary wood. The other shoots you pinch to slow vigor and turn into bearing wood. The spurs will from on those secondary branches so you have to train them just like the leader once the leader establishes dominance.

Your cherry is very unlikely to be on a rootstock that encourages precocity- more expensive for the seller. If it's termed size controlling without further designation it's probably mahaleb, which in most soils makes a smaller tree than mazzard but I don't believe it bears any younger.

In your climate, even a properly pruned cherry would probably take 6 years to begin bearing at all well.

    Bookmark   June 17, 2012 at 10:52AM
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Hman what I'm talking about is how some years we have what I think is a really mild winter without much chill and still get a really large and compact bloom on varieties beleved to be higher chill and then other years we get more cold weather and only get a meager and more scattered bloom from certain trees or no bloom at all in some cases. I'm sure there could be other factors that influence the bloom but I have always thought that chill was the major factor. I also think that there may not be enough research and testing done on what the chill requirements of alot of varieties actually are. Just my thought.


    Bookmark   June 17, 2012 at 4:50PM
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alan haigh

I don't know much about the affect of inadequate chill. Even where I was raised in S. CA I was at the base of a canyon and we got a decent amount of frosty mornings. I wasn't growing stuff which required much chill anyway.

However, I thought it was about coming out of dormancy with good vigor. A plant than would be affected by the winter before the last as far as flower set is concerned. In other words if the tree has inadequate vigor it's affect on flowering wouldn't be revealed until the following year, right?

    Bookmark   June 17, 2012 at 6:24PM
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Not necessarily a "TREE" question, but on my Indian Summer raspberries witch fruit on 2nd year wood, I have had terribly shaped fruit set, the berries are not forming the typical conical shape. The berries maybe have 5-8 huge druplets in odd shapes. The other varieties in the same row, had wonderful pollination and as thus fruit size and flavor are normal.

I will give it one more year, as they are producing a a ton of floricanes, but it is strange, and nothing I've found on the internet can lead me to a cause.

    Bookmark   June 17, 2012 at 7:05PM
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alan haigh

Scaper, I just realized that I worded my explanation very awkwardly. What I was saying was that a tree suffering from inadequate chilling might flower based on what happened the previous growing season, not on the affect of the subsequent winter.

I'm guessing that after the tree ran out of the energy reserves gathered the previous season it would begin to suffer the consequences of inadequate chilling. I don't know what the affects on the tree would be at that point, but those affects would probably come well after bloom.

Could be less vigorous growth, an inability to set flowers for the next season (no matter how much chill provided by the coming winter), smaller fruit or even fruit drop. You could probably tell me. If not, I bet Fruitnut could tell us all. It's out of my jurisdiction.

    Bookmark   June 17, 2012 at 8:13PM
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olpea(zone 6 KS)

Although not a total mystery, it's a surprise to me why my backyard has so much bird pressure (mostly robins). They dig up corn seed, pull up small corn plants to get to the seed. When the corn is ready to pick, the birds peel back the shucks and peck out the kernels. I have to net all my peach trees as they get close to ripening, otherwise they ruin bushels of fruit (Last year my notes showed they pecked 25 lbs. of peaches from one tree alone.) All my blackberries and blueberries must be netted or birds take all the fruit. Of course cherry trees must be netted or they take all the fruit. Apples aren't even close to ripe but this year birds have already pecked several apples.

What's surprising is a neighbor who has a couple cherry trees and the birds never touch his trees. He doesn't net the trees.

I think it's the large amount of mulch I use in my planting that initially draws the birds/robins. They dig through the mulch to hunt for earth worms. They must see the fruit as it ripens and go after it. But it's still surprising they are so single-minded they won't look for any food outside my backyard. I've kept everything much more netted this year so I don't think they're eating as well as they have in the past.

    Bookmark   June 17, 2012 at 11:27PM
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blazeaglory(10 SZ22/24 OC Ca)

Harvestman did you say you like juicy balls in a post above?

    Bookmark   June 18, 2012 at 1:28AM
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alan haigh

Yes, and I was aware of the double meaning- it was supposed to be a little funny, but I'm incapable of internet comedy. I swear, my show's much better.

    Bookmark   June 18, 2012 at 5:30AM
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alan haigh

Olpea, don't get me started on the unanswered mysteries of animal behavior in relation to fruit trees. OK, too late, I've started.

My robins, which are ridiculously plentiful on my property, leave everything but blueberries and mulberries alone (maybe you need those as a diversion crop). Of course they would go for cherries if I had them unnetted.

Everyone has crows around and only sometimes do they attack fruit but on sites they do everything must be netted. A loose net will do as they won't climb around under a net. At least that's the behavior of our crows. So far.

A very sane and intelligent client of mine told me of a very fat woodchuck making a 4' vertical leap from a dead stop to get above one of my baffles. Mystery- was this an olympian woodchuck or do Michael Jordan acrobatics come as standard equipment at the woodchuck factory.

When I told this story to someone else they told me of seeing a cotton tail rabbit clearing a 4' fence- that's a little cotton tail, not a jack rabbit.

I have sites nearby where the deer go as high as 7' to strip foliage and fruit. At my site they never go above about 5'.

My squirrels used to run up trees to get away from me but once I got a shotgun and slaughtered them for a few weeks they avoided trees and scurry in crazy angles through weeds and rocks at the slightest sign of my motion- even from a window. My wife's movement doesn't disturb them.

My son's theory for the squirrels is that I eliminated the local gene pool of confident, tree climbing when stressed, squirrels. That's a theory.

One thing I know, the behavior of same species wildlife vary a lot.

    Bookmark   June 18, 2012 at 5:51AM
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olpea - robins are territorial. Your neighbor's robins are probably afraid to go into your robin's territory for the fruit.

I've come to a very bad opinion of robins. Sometimes it seems they crowd out all the other birds. They steal fruit, they steal earthworms out of the soil.

And they crap everywhere. They perch on patio chairs and crap on them. When I put water out in the current drought, robins came right away and crapped in the water. Dirty birds.

I've told the cats it's OK if they add robins to their permitted prey list.

    Bookmark   June 18, 2012 at 9:23AM
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I was thinking about this mystery today! How do the insects and fungi and other diseases find my trees? Where do they get a map to my house. There is no orchard within miles of my house, no one really gardens to the extent I do in my area. Since I've planted my pome and stone fruit trees, I have every insect mentioned in this forum. How do they know how to get here?

    Bookmark   June 19, 2012 at 5:37PM
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alan haigh

None of you neighbors have amelanchier or crab apples? Same family- some of the same pests.

    Bookmark   June 19, 2012 at 5:56PM
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There are ornamental Kwanzan cherries in the spring, and flowering dogwood and Kornus Kusa, but thats about it.

    Bookmark   June 20, 2012 at 10:38AM
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alan haigh

No open land within a couple of miles?

    Bookmark   June 20, 2012 at 12:07PM
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