I have read some university papers about citrus, which say that after defoliation, citrus require large amounts of nitrogen, and that nitrogen easily leaches from the soil, unlike some of the other nutrients which persist. I tried increasing my fertilizer, but I feel that it's all just draining out of the gritty mix. Or, nitrogen is leaching out, but other nutrients are persisting.

Anyone have any hope to offer for this poor tree?

It is possible that there was so much root damage to it previously, that it is still in thr process of repairing roots.

How often did you fertilize and how much? You are right, they do need a good amount of Nitrogen, something that Foliage Pro alone will provide.

Did you stick to a regimend faithfully every week, or skip a beat here and there?
If not, you may think about a slow release mixed into your pots, or come up with a plan that allows you to fertilize more copiously and higher dosages.

What kind of 'water' to you fertigate with since pH can play a crucial role in uptake of nutrients, and what temps are your trees subjected too on a consistant basis, since this too can affect the ability for your trees to benefit from fertilizer?

Believe it or not, but I had a couple of citrus trees, one Ponderosa and a Meyer Lemon in particular that did exactly what yours did. I planted them into the gritty mix as a last resort when I first learned of the mix.
They had a lot of root damage due to neglect and a poor mix previously used which caused root rot on parts of the root balls. They had lost all their leaves and even a few branches.
Do you know how long it too for them to put out a good flush of leaves and healthy growth? Almost 2 years!
Yes. It wasn't until I started ferilizing correctly and exposed them to perfect conditions when, BOOM!
Tons of new growth took my by surprise that year!
And then of course there is the hope of a new sunny and warm season coming to help with all of this.
Be patient friend. There is hope:-)

Please, excuse any typo's. but work is calling me and I have no time to preview.

Mike:-)

Al

After the repot in July, I faithfully watered with FP. Well, I think I waited 2 weeks before using the FP. I used Superthrive during the repot. While the tree continued to suffer, I searched the Citrus forum and googled, looked at lots of images of citrus nutrient deficiencies, read university papers, etc., and everything pointed to nitrogen deficiency. I know that 9-3-6 is considered high in nitrogen. So I started increasing the amount. As I increased the amount, during the summer, it seemed to improve -- a little. Put out some new leaves, and the existing leaves greened up a bit. But it was only a little improvement for a lot of FP.

In the fall, I experimented with Osmocote scratched into the top of the mix. I didn't see much difference for better or worse compared to the FP. I expect that by now, the Osmocote is exhausted.

By November, we started getting lots of rain and colder weather, and I got sick. I let the rain and auto-watering (every 3 days) do its thing. Didn't see much difference.

We got some warm weather in December. I experimented with watering/fertilizing less, to see if I was over-watering. No improvement. By January, it seemed slightly worse, so I resumed watering/fertilizing.

This tree is outdoors on the deck, and gets flushed thoroughly every time it's watered.

The tree seems to do slightly better when I water with a lot of FP every day, and when it gets warmer. However, it only does SLIGHTLY better, and this is way too much work (for me) for so little improvement. I wanted to use a time-release rather mixing FP constantly.

I've tried adding various amounts of vinegar, or no vinegar, and it did worse with the vinegar.

I have seen other citrus in my area with some similar suffering. My neighbor bought 3 citrus and planted them in the ground, and his have lost a lot of leaves, and those remaining are pale. They're not as bad off as mine, and have produced a few fruits. I saw some in containers at the mall last week, that looked really similar to my suffering tree, with hardly any leaves but lots of blooms.