Help me understand tree nutrition distribution system to grow fruits

I start this thread because I have a 5 years old seeding peach tree that didn’t set a lot fruits , maybe only handfuls , but on one of the grafted branches set a lot of fruits. I have read local leaves support the fruits grow. What if the local leaves can’t make enough energy to support the fruits grow, does the tree transport rest of leaves/energy to support the fruits on that branches?

For starters if the parent tree is a seedling it make be perfectly normal for it to take years before it is ready to bear fruit. Chances are the grafted branch came from a producing tree, which means it was ready to produce as soon as it got big enough.

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The sending tree bears fruits last year and this year , it just didn’t bear a lot of fruits.
I am not complain about it doesn’t not bear a lot of fruits, I want to know how the tree distribute its nutrition and am wondering if the tree will move nutrition from other branches to support the fruits

Peaches are not my thing but for starters, what is the parent, and what is the grafted branch?

We are literally talking about two separate trees with their own idiosyncrasies. Yes, the grafted one will be affected by the parent being the ones providing the nutrients but it will still do its own thing; wake up on his own clock, flowers when it feels like, and put its own fruit in the quantity it feels like putting out. The rooted tree will do the same.

you ask a few questions, and to understand the answer you’ll first have to understand a little bit more about plant/tree anatomy.

If you goo to the phloem link you’ll also see pictures explain this.

You have 2 major transport “systems” in a tree. The Xylem, which mainly transports water and nutrients (absorbed by the roots) and some hormones (created in the roots, mostly actively growing root-tips) up to the leaves.
This transport is mostly 1 way.
The Xylem is located beneath/behind the cambium. And is consisted mostly of dead cells. Think of it as long tubes connecting the roots to the leaves. The transport is mostly due to negative pressure (the leaves “sucking” on the tube to “suck up” water from the roots.)

Atop the cambium is the Phloem, and the phloem can transport in multiple directions. And usually does so with positive pressure. The Phloem is mostly used to distribute resources such as sugar to other parts of the plant. Fruits for example is a nutrient sinks (sink means it uses it up, stuff gets transported to the sinks) While leaves are sugar sources. (they produce it) the transport from the leaves to the fruits mostly happens through the phloem. This transport is mostly by positive pressure. And it helps to think about it in that way, if there is an abundance of sugar. It gets “pumped” into the phloem under pressure. And than goes to places that need it. It tends to go to spots that need it nearby.

So this hopefully solves the first part of your question, how the tree transports stuff.

the 2e part is a little more complex. The tree does not just start growing if there is enough resources (sugar) at a certain spot. This is mostly controlled by certain cells and hormones. A lot of plants need a growing tip or bud for example to grow. Those are the special cells. And when they start to grow, or how they grow, (for example if they turn into a single leaf, or a new shoot) is determined by hormones. And often the balance between certain hormones. Like auxins and cytokines.

It’s hard to find specific scientific articles on this. But from what i read, flower buds get developed if there is enough resources (sugar) and the right balance of hormones available in the fall, or end of summer, when the buds mature.

This for example explains a disappointing fruit set after a year of to heavy bearing. The fruits where such a large sugar sink, not enough sugar concentration was left for the development of flower buds for next year. And this also explains why you usually get more flowers on a small twig that gets enough sun, vs one that’s shaded.

if i oversimplify it a bit, the roots produce mostly Cytokines, which get transported up. And a large concentration of Cytokines promotes shoot growth.

The shoots produce mostly auxins, those move downwards. And promote more root growth (this is why auxins are in rooting powder and help cuttings root faster) Auxins however suppress shoot growth. And you notice this with apical dominance (the buds below an active growing bud, don’t form shoots typically due to the auxins from the apical tip’s dominance (shoot tip)

This naturally keeps the tree in balans. If you have a tree with lots of top growth, and little roots. There are more auxins than cytokines. And thus top growth pauses, and root growth gets promoted by the hormones.

If there are more growing roots, than top growth (for example after heavy pruning) there are little auxins produced to suppress side shoots from forming, and loads of cytokines transported up that stimulate shoot growth.

From what i understood, the tree also uses the balance between the two, to determine if it’s mature enough to flower.

Mostly this is determined by when the roots reach their “mature size”
And the lack of cytokines compared to large above ground tree slows down growth, which leads to accumulation of sugar that than triggers more flower bud formation.

This explains why dwarfing rootstocks dwarf, they usually don’t form super large root systems, they stop expanding at a relatively small size.

And also why a seedling stock in a tub/pot, can still start bearing early. your artificially limiting the size of the rootsystem.

this is an old but still great YouTube video about the xylem and how it transports.


Yes it will. So if only one branch has fruits you can leave more than normal on the branch. The tree will move sugars from the non bearing branches to the one with fruit. Just be careful that the bearing branch doesn’t break.


Like music in my ears😄

wow! Lot of information. Thanks for explaining all. I understood those straight forward ones, fuzzy on others, well, keep learning

Oscar, funny you got into that. A few days ago i was digging into an interesting study that tested the effect of dwarfing a tree by just grafting the bark to them. It looks like even established trees could be arrested by a few strips of bark, with a full girth bark transplant achieving the most. The researchers also tested grafting the bark backwards which also achieved dwarfing.

you might have to read my post twice, to understand it.

But please let me know what wasn’t clear or what doesn’t “make sense” and ill try to explain.

Can you post a link to that research?
By transplanting bark, your only “messing with” the phloem. And maybe the newly deposited xylem. However usually some cambium of the stock remains in a bark graft. Would be interesting to test out, which genetics the xylem would get behind a full bark graft of another variety. I could likely test that out by grafting bark of B9 on M9 (or another non red wood apple) or vice versa, and checking the wood colour after letting it grow 1 or 2 years.

I read somewhere it was theorized dwarfing interstems work because they limit the transport / or brake down certain hormones.

I remember also reading about the bark grafts with upside down bark. If i remember correctly it reverted to full size after a few years, the dwarfing effect was temporarily. I’m curious if you however graft bark from a dwarf rootstock, if the dwarfing effect would mimic interstem dwarfing and be permanent.

Page 12, second paragraph, but the interesting stuff starts earlier. This paper has a very good bit on my specific problem of a mid winter meltdown.

There are also some interesting bits regarding hormonal functions that affect dwarfing on page 16. For instance:

Auxin levels are generally lower in dwarfing rootstocks compared to that of more
vigorous types. The bark of dwarfing apple rootstocks is known to destroy auxin, perhaps
through oxidation, which may account for the lower levels found in these trees (Lockard
and Schneider, 1981). Faust (1987) however stated that low vigour seedlings had
excessive level of auxin and gibberellins in relation to their low growth ability. A lack of
auxin metabolism may cause its accumulation to the level, which negatively affects shoot

So the bark from dwarfing rootstocks may contribute to low availability of auxin, but the mechanisms by which dwarfing occurs are not completely understood. Namely how some dwarf seedlings do have excessive levels of auxin, pointing to a blunting of the auxin metabolic pathway instead…

Regardless, practical experimentations seems to support the effect of bark transfer on dwarfing, whether or not we understand why that is so.

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