Cristofre, wrote..."The WHOLE tree flowers, not just the nodes above 1,250"

When a citrus tree finally reaches the maturity node and begins to flower and fruit, the whole tree does NOT flower and produce fruit. Only that portion of the tree above the maturity node (node 1,250 in your example) will flower and produce fruit. The entire tree below the mature node will forever stay juvenile and never flower. Therefore, for seed grown trees, the grower must reach high into the tree's top, to pick any fruit. - Millet

I question that, as my Faustrimes begin fruiting on the lower branches. The higher branches seem to bloom the following year.

Millet this is new info to me, I've never seen any reference to seed-grown trees only flowering and fruiting at the very top.
I just assumed that the whole tree switched on at the same time.
(I've yet to have any of my seed grown trees reach flowering / fruiting stage)


Another curiosity, if a certain citrus is propagated typically from cuttings, say, a Meyer Lemon, is it possible that there exist trees that have node counts in the thousands, hundreds of thousands?
(take a cutting from the top of a tree, grow a new tree, take a cutting from the top of that tree, start a new tree, etc. )

I don't know about hundreds of thousands, but if a cutting was taken from the top of a mature tree, rooted and a new tree grown the node count would start at the remembered node count, and go up from there. Then if another cutting was taken from the top of the new tree after it had gown tall, rooted and the second tree grew tall, and etc. etc. the node number would keep getting higher. However all this would really not mean much, and would really not be very important. Mature node 600 is no different from node number 6,000. - Millet

Unfortunately, I am still quite new in citrus culture. But I remember some observations of Mitchurin, the favous Russian breeder of fruit trees. Those observations may contribute to the theory of node counts. Mitchurin observed that a plant needs a certain time to fruit. During this juvenile phase it adapted to the climate and showed certain changes in its growth character. Mitchurin developed a complicated system to influence these changes. When it first flowered it took four years until the plant reached its final form of growth and its final fruit character. Once reached it was unchangeable, a stabile variety.
Now, in case that the tree send some shoots from its trunk these shoots were juvenile in character again. That means that the plant only develops as it is growing. So an indication that the theory of node count is right. Mitchurin therefore recomended that everybody who wants to increase a self-bred cultivar take the budwork from mature twigs from the end of the branches.
What speaks against a simple node count theory: Some trees never flowered. In order to force them, Mitchurin grafted twigs of aduld trees on the branches. And not to long after that, the whole tree flowered. Once the tree flowered Mitchurin removed the grafts. But the tree continued to flower and bear fruit. That might mean for the node count theory that the number of nodes might indeed matter but only what regards the so-to-say booster detonation of flowers. Once they appear phytohormons might set all the parts of the tree in the mode of leaving behind their youth.
Something else against the node count theory: It is possible to bring twigs from seedlings to flowers in quite a short time when they are grafted on adult trees. Mitchurin did that with success but also warned that often the grafted twigs do not flower earlier than the yound mother plant but later. He thought that were do to the shock of the grafting procedere.
Three questions remain for me: First, does this trick with grafting mature twigs only work when the tree has principally produced enough nodes? Second, how long do shoots from the trunk take until they flower? And third, do Mitchurin's observation apply to citrus trees or are they different?

OK here is what Dr. Manners had to say about no fruit will develop below the point where the 1st maturity node finally developed. Dr. Manners is answering a post by Nero. First I have reprinted Nero's post and then Dr. Manners answer.

------
• Posted by nero (My Page) on
Thu, Mar 22, 07 at 23:36
what about regarding the part of lower nodes not producing flowers/fruit. i guess my question is that if lets say node 100 on the top part of the tree is producing flowers, cant node 15 on the first branch produce as well?


•Posted by malcolm_manners 9b C. Fla. (My Page) on
Fri, Mar 23, 07 at 7:33

Nero,
No, never. That's why century-old seedling trees continue to produce fruit in the top of the tree, way out of reach unless you have a ladder, but never on the lower branches.

---------------

I find where Dr. Manners agrees with my polition. Dr. Manners is certainly the citrus authority on this forum. If he says no I think we can believe it. - Millet

We do know that there are grafted varieties of orange that are nearly thornless, while seedling oranges are very thorny.

Thorniness is a characteristic of juvenile growth. But some people observe that even their bearing trees (grown from seed) continue to have extremely long thorns, while commercial grafted varieties are nearly thornless.

So, this is an advantage that I see with grafting from a bearing tree (which was grafted from another bearing tree, etc. etc.).

This new graft, let's say its node count is now up to 100,000, is so mature that it has lost most of its thorns.

This is only wild speculation on my part though.

Not sure if that made sense.

Outside.
I did have one growing for years in a greenhouse (in the ground - not potted), but I moved it when it grew too big. They turn into a small tree and the thorns are dangerous in a greenhouse!

Node count is the way we can measure the maturity of a tree seedling. Underneath this is the actual process controlling first flowering. In plants this is likely to be under the control of plant hormones. Either a hormone chemical builds up to trigger flowering, or a hormone inhibitor builds up to stop another chemical preventing flowering. It may be that a flowering gene is switched on by the hormone, this would explain why mature scions dont revert to non flowering and "remember" their node count.
Citrus cultivars are probably hybrids of several ancestral types, so there may be several versions of the flowering control mechanism in any cultivar. Any thing with lime or microcitrus in its ancestry seems to be faster flowering than those without. Some microcitrus seem to have a very low node count to flower.
Triploids have 3 sets of all genes, so would have three sets of the flowering control mechanism,( dipolids 2 sets, tetraploids 4 sets ). This may explain the long flowering times of some cultivars, but their exact ancestry may also be important, as to which ancestral genes they still retain?