My Calamondin leaves always seem to be wilting. Does this have to do with too little turgor pressure?
I wonder if it's because the roots aren't capable of taking enough water, or of too high salt content (hypertonic solution). How should this be treated?
Pruning some of the leaves? (if the roots are not capable of taking enough water, damaged etc.)
Or watering a few times with distilled water (isotonic solution)?

Do all leaves wilt or just the new ones? Are they constantly wilted or only during certain times of the day? New leaves on some of my trees will wilt when the leaf temperature rises too rapidly for the roots to supply water but they recover quickly when the temperature stabilizes.

They're always wilted. Especially after sunlight. And all of the leaves do that. Except ones that the tree produced still in the nursery, because they seem thicker.

As opposed to normal Calamondin leaves (not my tree):

In summer there was a drought, that caused some root damage and made the leaves look like this:

I'm hoping that this year, after I repot and prune some of the branches, the new leaves are going to be fine. This is my biggest concern.

You may have dry zones that are never becoming saturated or wet, or if they are, they could be drying out quicker they other areas, giving off the appearance the medium is wet when certain zones are dry. it if difficult to tell though. Wilting normally has to do with over or under watering, with CHC it is nearly impossible to over water so I believe it is under or inadequate/uneven watering. You are always going to have this issue with the medium you are using, I would replace it with something similar to what the healthy looking tree is potted in. just my opinion.

The tree IS growing in the same medium as the healthy plant. Both trees (mine and not mine) shown in pictures are from the same nursery. Here's what is says in their website care advice, in the repotting section: "The plant has been grown in a pine bark and peat mixture (50:50)."
As I have a rule of potting my citruses in the same medium I got them in I potted them into 50:50 peat and pine bark mixture.

I've never used CHC because I wasn't able to get it.

From what I've heard over watering causes leaves curling inwards (like tubes)

Right now it's growing in a 4l pot, I usually water with 1l of water/fert. solution. So that's 25% of the pots volume, when recommended minimum is 10%.

Once in about two months I flush it with a lot of water. And after that the leaves go upwards for some time, but then they wilt again.

I can't wait to repot and see how the new flushes turn out.

By the way, has anyone ever been able to get such dense Calamondin leaf growth, as in the picture of the healthy, beautiful tree, grown outside in Portugal's sun, on a windowsill ?

Wow that looks like CHC Anyway, there appear to be differences between the two mediums. Are you using GROUND pine or fir bark? by the look of the photo it must be chips or otherwise larger pieces or bark. This could be the cause of the uneven water distribution.

And what you herd about leaves rolling up when over watered, this is NOT correct. Citrus leaves will droop when over watered (starved of oxygen) and droop when under watered as well.

To me, it is your medium, something is wrong. Did you mix this yourself?

Then this could be the problem. You want to use Ground pine or fir bark, its ok if some chips end up in there but the majority will be ground. With all those chips you are currently using, you probably have big air pockets in the medium, which will cause the drooping. They also will not hold water well and dry out quickly and unevenly.

With trees at the nursery it may look like they are only using chips because eventually they settle to the top, but under it the larger pieces of bark is ground material (just like the image showing the healthy tree). this is what misled you. I would go to the nursery and ask for some of there mix to make it simple.

You said "dense growth" , well this is what a meyer will do to a citrus grafted on him.
More compact and more bushy citrus tree , isn't it what you are looking for?

This is the Calamondin grafted on Meyer .... in summer 2010

Oh, you did get what I was asking. My fault. Sorry!
Yeah, your tree has the beautiful dense growth I'm looking for. Tell me how have you been caring for it (location, sunlight, temps, soil etc.)?
And it was exclusively kept INSIDE, right?

yes under a 3x18 w fluorescent lights, CHC , low on water ...21C temp


Here is a picture with the tree , it does have a spring flush , but also starting to lose a few of the bottom leaves due to the fact of no light area

Well, the fact that you're also using bark based medium gives me hope