Flying dragon vs troyer citrange vs trifoliata

JakfruitEttiquette says...
FD is the smallest tree size, about 1.5m, but very high fruit/space ratio per tree.
Tri is about 3m, and commonly used on heavy grey river clays around here, in pref to other rootstocks. FD is also a type of P.trifoliata.
Citrange is an orangeXtrifoliata hybrid, final tree is around 5m, not used on same soils here, perhaps others may know about red clays etc.

JakfruitEttiquette says...
Not sure about FD to 3m, probably if grafted to orange, will be bigger than grafted to mandarin. FD is dwarfing, mainly due to longer winter dormancy period, compared to Trifoliata. How much warm weather does Dural get??

Boris Spasky says...
FD is best suited for pot culture.
Unlike dwarfing apple rootstocks, FD is not used commercially in citrus groves. The main reason which the nurseries won't tell you is that FD actually produces smaller sized fruit and lower yields. Jakfruit, you are confusing FD with tri in terms of cropping efficiency. It also is incompatible with many more mandarin varieties than tri.
FD is a rootstock for the retail market for those who have the quaint notion that they can have a worthwhile crop from a 1.5m tree.

Brain says...
I have a lot of citrus on Flying Dragon, so will give my 2 cents on FD. :)

My FD citrus are growing in pots and 1.5m seems to be the norm but I am with the view that it can reach 3m if grown in the ground. (I have a daisy on FD and it's 2.5m) Also, FD has variable characteristics, i.e. the seed that the FD germinated may be quite vigourous. I've had first hand experience when I brought 2 doz FD rootstocks and saw the difference first hand. I even found a US paper where the result claimed up to 25% of FD is not true dwarf.

As for fruit size, in general, the fruit size of 75% to 100% can be achieved. I've achieved full size for oranges, mandarins and limes.

If the variety of citrus you're growing tends to overbear and you don't thin, you will definitely get very small fruit.

The other catch with FD is, you will only ever get a handful of fruit per year. For example, a 1.5x1.5m tree might only give me 2 to 3 orange/mandarin per year. This is only because it's s small (and young) tree, but with proper nutrition and care, this should increase. I.e. I've gotten 20 limes from a 1m(h)x1.5m(w).

This is what I'm trying to do. I'm aiming to establish a strong frame for the FD citrus (let's face it, when you buy one, they are sticks). Then shape it like a 'Christmas' tree with 3 or 4 strong side branches. Then fertilise the hell out of it to give it a dense canopy/leaves structure. Then and only then the FD would be able to support more fruit.

If you wants lots of fruits from one tree, go for say trifoliata. But if you want lots of varieties and don't have the space, the FD is a good consideration.