what are the common or top 3 reasons that your potted citrus taste sour? Watering issue? Fertilizer issue? Soil? or...

Wrong variety; picked too soon; not enough sun.

Temperature and growing duration. The same problems here, to short growing period and average temps too low or too short.

Or young trees...

The original question did ask about "your potted citrus", so not enough sun, too low average temperatures may be relevant - if not in Texas.

It's interesting that, in my experience

Quote:

Watering issue? Fertilizer issue? Soil?

has little effect on final taste or sweetness. These issues determine how well a tree grows, whether it flowers and sets fruit, and whether a reasonable number of fruit develop and reach maturity. Once a full size fruit is hanging on the tree, the final taste and sweetness is then - within reason - independent of these external factors.

Citrange,

your correction is absolutely right! I just automatically assumed that Charlie tasted his own fruit grown in hou and did not like it.

Your observation about water/fertilizer is very interesting. It gives me a hope that my Navel should taste grate even if I mess up water and fertilizer.

It would be a better bet to get some sour citrus varieties when not living in the right climate for sweet citus then...
Indeed, my bearss lime and meyer lemon trees produce nice tasting fruit, while the oranges on my moro tree do not taste all that great. Oddly, the oranges weren't sour. They were sweet but not the kind of sweet one would expect from an orange. The taste was rather dull when eaten. When juiced, the juice was tasteless. There was no blood coloration either.
I wonder what my star ruby grapefruit will taste like...

Commercially, sweet citrus fruit are tested for their Brix value (actually degrees Brix). This is a measure of total soluble solids, mainly sugars. Higher Brix means a sweeter fruit; higher Brix with high acidity makes for a stronger flavoured fruit. Some regions do not permit sales of particular varieties below a certain Brix value, otherwise consumers might come to associate that variety with lack of sweetness.
In Texas, the strong summer sun should guarantee high Brix. Some of the best grapefruits are grown in Texas.
In Belgium, like here in England, I doubt you will ever grow a sweet grapefruit. Some varieties of orange (eg Trovita) do get acceptably sweet, but in general more acidic varieties will be sour; less acidic varieties will taste bland. I have given up trying to compete with Mediterranean grown shop-bought oranges.
There is an interesting article about growing sweet fruit in New Zealand - a cool citrus region. It suggests heat at the small fruit stage is important - even if this means later flowering. Full sun on the maturing fruit also raises fruit temperatures well above ambient, so improving sweetness.
This suggests my growing conditions - early spring flowering in the greenhouse, followed by a long, cool summer outside - are completely wrong for sweet fruits!
See
http://www.hortnet.co.nz/publications/science/r/richardson/mandrin.htm
Mike/Citrange

I don't expect to grow any quality fruit either... I just want to keep dreaming!

And I don't really mind sour fruit, but I don't like bland at all. Oranges that are currently on the market here aren't any good either, they really have a bland taste. I'm eagerly awaiting the new citrus season!

As others have said young tree, leave fruit on tree longer and more sun. I also cut down on water as it gets closer to picking fruit.

Young citrus trees normally do not produces quality fruit until the tree reaches at least 5-6 years of age. After that the fruit generally improves each year. A 20 to 25 year old tree produces its best tasting fruit. . Millet (-405-)