I have my red clementine tree for about a month now, see link.

The tree had lots of new growth and carried lots of flowers. The flowers have all opened and are all gone now. Some of them seem to be growing into fruits (did some pollination myself).

But most of the inner canopy (older) leaves have fallen of since I got the tree. Even then, the canopy still appears good. What I'm a little worried about is that it appears like the young leaves do not turn dark green. Also, there hasn't been any new growth (flowers nor leaves).

Could this be the fertilisation? Until now I've been using citrus fertiliser with NPK 5-7-6 + micro nutrients. This fertiliser does by far not match the optimum 5-1-3 ratio that I have been reading about here.

I have now found another citrus fertiliser with ratio 11-3-6, which is a much closer match to the 5-1-3 ratio, but I have not yet applied this.

Here are some pics of the young leaves:







This is what the tree looks like today :

If these are the recent pictures --your tree is fine. Citrus grow in spurts called flushes--new leaves take time to develop the solid green of older leaves. Old leaves get discarded after a yr or so.

It takes a month or two before enough nitrogen completely enters the new leaves. After this happens the new foliage will become dark green. The 11-3-6 is a much better formulation then the 5-7-6. You don't mention whether the 11-3-6 contains trace minerals. Be sure that any fertilizer you use contains trace minerals. - Millet (990-)

The exact composition is on the bottle, but it's there in Dutch and French. No English, and I'm not very good in translating that kind of stuff...

I'll give it a try though...

11% N of which:
1.7% Nitrate N
1.0% Ammonium N
8.3% Urea N

3% P2O5 (phosphor pentoxide)

6% K2O (kalium oxide)

Micro nutrients:
0.010% B (boron?)
0.002% Cu (copper)
0.025% Fe (Iron)
0.017% Mn (Manganese?)
0.001% Mo (Molybdenum?)
0.003% Zn (Zinc?)

I hope this is clear...

You dont list Ca calcium, Mg magnesium, S sulphur.
Ca and Mg may not be included in all ferts, as they can be supplied by lime or dolomite when pot mix is made, or as trace quantities from groundwater.
S could be supplied from gypsum at mixing, but maybe you want to double check, as Fe is most commonly supplied as FeS iron sulphate( but could be Fe oxide or Fe chelate) Even Mn and Zn are often supplied as sulphate.
Unless all your minor elements are Chelates etc, they must be FeX, MnX ???
although not listed that way on all fertilizer labels.

Normally, all the calcium a citrus tree requires, is supplied by either well water, or in your municipal water. It is easy to find the calcium content of municipal water, by simply telephoning the water company and asking. -As for the magnesium, dissolve 1 tablespoon of Magnesium Sulfate in a gallon of HOT WATER, and pour the cooled solution over the root zone 3 or 4 time a year, or if a deficiency occurs. - Millet (990-)

There's something about chelates on the bottle too (I have no clue what chelates are ):

Copper, manganese and zinc : EDTA chelate former (hope I'm translating that right, if not please correct )
Iron : DTPA chelate former

That's all I can find on the bottle.

The municipal water contains quite a bit of calcium here. Might even be too much...

What are the symptoms of magnesium deficiency, and where could I find Magnesium sulfate if needed? I'm not in the States, supplies may be different here...

I was wondering if mixing the 2 of them will get the right fertilizer ?

Marc, Magnesium Sulfate, is common Epsom Salts. Epsom Salts should be readily available at most any hardware, super market, or even most general food stores. - Millet (989-)

OK, thanks everyone for your helpful replies!