You can plant any number you prefer, but I have some thoughts to share about that.

A) Your question calls to mind whether or not the propagules will remain together in the pot as a group planting? IOW, will the plants be living in a clump, or will the propagules be getting their own pots after rooting has taken place?

B) Whether you start one cutting in a given size pot or 10 cuttings, there isn't going to be a big difference in the amount of biomass produced by whatever volume of soil was required to fill the pot. IOW, the collective mass of 10 propagules rooted in a single pot isn't going to be notably different than the mass of a single plant. However, while the o/a mass will be comparable whether 1 or 10 plants, the size of the plants (being 10 in a pot) will be roughly 1/10 the size of the single plant in a pot. In most cases, root congestion is going to end up being the primary limiting factor. At the approximate point in time where the root mass becomes congested to the degree the root/soil mass can be lifted from the pot intact, lack of growth will already have become a limiting factor.

C) Using multiple cuttings in a single pot to provide 'the look of fullness' isn't necessary. You can make a single plant as full as you wish by pinching judiciously. This is true of almost any plant with a branching habit.

This ^^^ is one of the duck-foot Coleus, the growth habit of which runs to leggy and pendulous/drooping. Judicious pinching has helped me to create something much fuller than the plant would be after being left to its own devices.

Another trailing coleus ^^^, same story.

Does it depend on the size of the pot? Let's consider a vase with a diameter of 5 cm and another with a diameter of 10 cm. The size of the pot won't have a lot of impact on the difference in size of the plants. Because root congestion will become a limiting factor, the planting with 10 trees will increase in mass somewhat faster, and produce a larger volume of roots faster, which means growth will slow (due to root congestion) sooner. The single tree will take longer for the root volume to build to limiting proportions, so growth will still be strong even as the multi-tree planting is slowing. The effect is, the single tree should 'catch up to' the amount of mass produced by the multi-planting.

All this, of course, assumes that all else is equal - same amount of fertilizer, light, temperature the same, watering practices the same .......

Al

Thanks for your quick reply. I consider you a great expert and a person who is always ready to help others.

You have perfectly grasped the meaning of my question. The purpose for which I always planted more cuttings in the same pot was to get a fuller plant. I thought that this was done because in general the ficus benjamin are sold like this: more trunks in the same pot (trunks that often then merge over the years). But I have read what you write about root congestion and for this reason I asked you this question.

PS1: the propagules will remain together in the pot as a group planting because I would not know how to separate the propagules once they have taken root and the roots are intertwined.

PS2: in the past I have rooted the cuttings in water but now I want to put them directly in the ground not only because I have read that you do not agree (the roots that develop in water are different from those that develop in the soil), but also because it becomes more stressful to manage the cuttings first in water and then in the soil. I just hope that the percentage of engraftment in the soil is the same as in the water.