[cicerone]

I planted this orange tree about 9 months ago and roughly 3 months in it started yellowing on the new leaves and now it's in a very bad state. Possible reasons:

1. Root rot? The soil is clay (fairly loose and well-draining but clay all the same). Also, I think my in-laws watered it when I was gone and then I would water again on the weekend (and then it would rain) so it never dried out completely. I'm letting it to do that now but maybe too late.
2. Needs fertilizer? I threw some standard citrus fertilizer on it but too early to tell.

Anyone have experience with this?

[ezeiza]

Totally yellow leaves intermixed with totally green foliage is a sign of overwatering. Is your tree on the ground or in a container?

Do you know the golden rule "If in doubt, never fertilize"?

[cicerone]

The tree is in the ground. I'll let it dry out and see how it looks after a week. The rainy season is pretty much done. Probably one more light rain event for the entire month of May and then nothing until November.

Yes, per the golden rule, that was just a dumb move based on the first thing that popped in Google for "Orange tree yellow leaves". Then I put two and two together and realized everyone in the household was probably watering this poor tree to death when it just wanted some heat and time between waterings to get established... hopefully she'll pull through with a dry week or two.

[ezeiza]

For citrus and other subtropical origin plants, soak well and then let it dry a bit, then soak well again, etc. A permanently wet soil is worse than drought.