@HarunobuI want to talk to you about flower removal. Do you agree with him that it's not good practice to remove flowers before the tree has opened them? It's common practice to remove so the tree don't spend the energy.
To me something within the tree has to "suffer" (for lack of a better word) when the tree can't go through it's flower/seed cycle . I'd rather do what he said and leave the flower to just when it opens, then remove.
You'll know the science behind that....?
I actually agree with Warren on the first point on flower removal. I said I agree with many things he said. And I am also glad he pointed out that satsuki in Japan is not a bonsai hobby. It is a satsuki hobby. I think he did an excellent job explaining that. And I learned something about plants being more valuable, or less so, based on if they fit into a specific category for display/competitions.
But back to flower removal. The point some people sometimes made is that since flowers 'take energy away' from the tree, they should be removed in spring, to prevent the tree from flowering. And with energy, let's define it more precise as carbohydrate resources. Since the azalea actually produces the flowers in autumn, removing them in early spring does not conserve the carbohydrates the plant spend to grow these structures. They already grew. They only need to mature. I am not sure myself if this means the base tissue is there and it expands and more cell layers are added. Or if all cells are already there and they change shape. Probably, they do need to produce the pigments, because when I remove a flower bud early and open it up, it is all green. I am not a botanist and there are many resources out there about flower development that I have not read. But I am not a professional in botany/horticulture/bonsai.
So Warren proposes to prevent flowering by pruning in late summer/early august. I think this is an excellent suggestion. Even removing the flower buds in late autumn is kind of pointless. If you want to prevent the plant from spending carbohydrates on flower buds, you have to manipulate it so that it does not attempt to grow flower buds. Physically removing them as it is trying to grow them is not how you would save those carbohydrate resources.
But then Warren says that if you do not prevent flower bud formation by pruning early autumn, you should remove the flowers as the first flowers open. No sooner, no later. He says that if you do not remove them exactly at this moment, the hormones inside the plant get confused. And then I think he suggests or means that this will lead to less strong growth. Now, I cannot definitely say this is false. But it does sound very strange to me. Because it would mean that if you remove the flowers as they open, the plant does not get confused. But if you do so a week earlier or a week later, it does. Why would it get confused? In nature, flowers can be removed physically for many reasons. What does an azalea plant need to do to reproduce? It needs to set the buds. Then it needs to swell them and open them up as flowers. And then it needs to grow seed capsules with seeds inside if the flower is pollinated. Some species of flowers will try to grow aditional flowers when the flower gets removed. For example, the sunflower. So there, yes the plant gets 'confused'. Or to be more specific, removing the flower will result in the plant growing many tiny flowers. Which is not what you want. Azaleas don't do this. So what exactly is this 'confusion'? I would postulate that through millions of years of evolution, azaleas can deal fine with their flowers being physically removed. They know they only flower once a year. So when they get removed, they will just do their thing and try again next year. I don't see how it can be explained that when you remove them too early, or too late, the plant refuses to grow for a bit. It would mean that the succesfull opening of the first flower would trigger to the entire plant 'flowers are opened, mission accomplished' and that this produces a hormone that feeds back with some signaling pathway into the growth habit. That would explain the very specific timing. It might be true, but like I said before, this is the first time I ever heard about this hypothesis. And I know that the nursery industry has no problem growing an azalea plant from cutting into a flowering plant without letting the plant flower, at all.
And if this theory is true, you would want every flower on the plant to completely open, before removing it. And if true, I don't see how removing it later is also worse. The theory is based on a certain hormone only being produces when the flower opens, to signal to the rest of the plant 'flowering initialized, proceed to next step'. Since hormones are molecules that diffuse through tissues and not some electric signal on a nerve going to a central nervous system, you would need to remove every flower as it has opened. Under this theory, removing unopened flowers when the first flowers have opened would still mean that the hormone is not being produced by those specific unopened flowers. And besides, if you remove the flower completely, and not just the petals; it is gone. Tissue that is physically removed cannot produce hormones to signal the rest of the buds in that twig to start growing faster.
This is why I find his theory strange.
From my experience, flowers increase the water requirements of the entire plant. So if you repotted your plant and in the process removed part of the roots, I can see the advantage of removing the petals (and probably the stem and ovule because you obviously don't want it to spend carbohydrates producing seed). And it makes sense that the petals evaporate a lot of water since they are thin, have a large surface area and likely don't have the same water conserving mechanisms that normal leaves have, ie stomata closing, hairs, etc.
I also see a mild effect of flowers inhibiting growth. This is not complete, because obviously shoots grow from the base of the flowers. This is more obvious in satsuki than in kurume. From my experience, when removing flowers from kurume, they start to grow earlier than branches where you keep the flowers. This makes sense because kurume flower first, grow second. And if flowers produce hormones inhibiting growth, removing the flower physically would remove this inhibition. But on satsuki, this mechanism cannot be as strong as in kurume, because if that would be the case, the satsuki wouldn't grow until it has flowered in late may/early June.
Therefore, I back Warren's suggestion of pruning to prevent flower bud formation altogether. I back the notion of removing flower petals to reduce water requirements and give plants an easier time producing enough water, especially to plants that had their roots pruned. But I don't see why you need to wait until they open. And I back the notion that flowers inhibit growth in kurume and that removing the flowers will speed up the initiation of new buds growing, but only on that specific branch. And I propose this same mechanism is likely present in satsuki, but much much weaker as satsuki obviously grow shoots while flower buds are present. To a degree that it likely has no meaningful effect. I think whether satsuki pause or slow down the growth of these shoots as flowering starts is up to debate. I have seen no anecdotal or scholarly evidence for the notion that the first flower opening acts as some hormonal checkpoint that the plant has to reach to proceed to the next growing step unconfused, besides this Warren video. If there is evidence for it, I'd like to see it and I will be convinced. The fact that Warren styles amazing bonsai does not fit my criteria of evidence. I fully accept that you can do what Warren says and have an amazing bonsai that can win awards in Japan.
And if the plant 'suffers' when it cannot set seed, you would allow it to set seed up to the point the seed capsules split open and spread around the seed. This at the cost of carbohydrates but at the gain of a more favourable hormonal cycle. Warren says you should go through part of the cycle, not all of it. I think nature is perfectly able to prevent confusion in this cycle and realize the flowers were physically removed and respond accordingly.
