I would give it more food and maybe a bit more water; your leaf size and color are a bit underpar for a Cara Cara. At that size on a dwarfing rootstock, your tree should be producing oranges. I have Cara Caras smaller than that that are producing a lot of oranges. The amount of direct sun it gets is probably enough if the tree is adequately cared for, the temperature and the length of daylight are as important as the direct sun; and the concrete walls should help with the warmth.

Johnmerr, thank you for your help & suggestion! So far, I fertilized twice this year (Feb. & June), I didn't fertilize in Oct., my bad. We're in zone 10 & from the past, it flowers later on this month. Since, it hasn't flowered yet, I can still fertilize it now?

I'm still learning about watering schedule. I tried to control the watering, so it doesn't get too wet. I notice in the past, the leaves get yellow when watering too much. Now as you can see from the picture, they're more green then yellow. You recommend that I increase a tad more?

One thing though that happens year after year is that, after it flowers & the baby fruit set, there'll come heavy pouring rain for couple of days, then all the baby fruit drops. I don't know what to do.

Please advice. Thank you!

Yes, you can and should fertilize now. The fruit drop, after being set is not due to the rain; more likely the age of the tree combined with not enough food. Heavy continuous rain can cause matting of flowers if the bloom is heavy; if you notice that and the appearance of black fungus, it is anthracnose and can be combatted with a copper spray.
I am not sure about more water; you would have to check your soil for moisture; but be sure you are putting enough fertilizer, putting it at the dripline of the tree, and watering it in deeply.

This post was edited by Johnmerr on Tue, Nov 4, 14 at 17:39

There were no black fungus on the leaves, just yellowing of the leaves.

ok, will fertilize it this week. Thanks!