I too would cut it way back..But the very first thing I would do is pull it from the container and really see what is going on with the roots..Can you do that and take a pic of them?

Will that tree get LOTS of sunlight ? And do you know if your friend ever fed it?

It looks like it's under fed, over watered, growing to tight in a pot and did not get direct sun...What zone are you in? What kind of temps do you get? Are you in a very warm climate?

If your tree has lost a many root, it is best to cut it since the amount of roots left behind can't keep up with the top growth which would explain such a lack of leaves and twig die back..

Keep the soil surface clear of dead leaves and debris as that can cause disease and creates places for insects to hide and breed. I agree with Laura and Mike. The soil looks too heavy and dense and the roots are probably dying from lack of oxygen around the roots. The 5-1-1 Mix that most of us use as it is a light airy mix that citrus grow well in when grown in containers is posted often so you will find how to make it easily by searching this site - 5 parts fine bark (many of us use Repti-bark as it is easy to find in pet stores or online), 1 part peat moss, and 1 part coarse perlite. Also some people add 1 Tablespoon per gallon of mix of Osmocote Plus (slow release fertilizer with micronutients) as a backup to their fertilization schedule if things get busy and they don't have time to fertilize with a liquid fertilizer, such as Foliage Pro, sometimes. Also add 1 tblsp. of lime to the mix as the mix is quite acidic. Citrus like a pH of about 6. Once you get your tree in the right mix, then fertilize with Foliage Pro by DynaGro's Grow as it has the right proportions of macro and micro nutients that citrus trees need to grow well. Follow the directions on the label. Welcome to this discussion group. Keep asking questions if you don't understand and we will help you get that tree growing, blooming and giving you fruit.

Cory

Everything that could have possibly been done wrong to that poor tree has been done wrong, and then some. Looking at your picture, the poor tree has been grown without the proper light, is root bound, struggling with a root zone high in soluble salts, especially bicarbonates, and has not had the medium flushed out with clean clear water in a great while. If you want to grow a lime tree, at this point I would go out and purchase a new lime tree from a good nursery and start over. - Silica

Don't cut it, definitely don't cut it.

Why are people recommending to cut it?

Let it do its thing. Cutting back will only achive removing half of what leaves are left.

Dont repot. Downpot. Don't change the soil. Just down pot.

Let it dry between waterings.

The goal is to not shock it anymore. Removing what leaves and branches are left will shock it. Removing the soil will shock it. Leaving it in a huge container will cause rot issues which will shock it.

I understand what you are saying Pip, but heck, it is already in such bad shape...I would definitely not cut the branches that have leaves, but the ones that are just sticks, I would hack back.

We are heading into fall and winter. I do not know where the OP lives and that would be helpful to know. I would probably first make sure the plant is getting even watering -- not too much or too little. With so few leaves, the medium will have to be watched that it doesn't remain too wet. The plant can hardly take up water without leaves. Perhaps add some very diluted fertilizer upon watering. I wouldn't expect a whole lot of growth in the Fall as the days get shorter, but perhaps in a sunny window, it might get reinvigorated.

THEN, next summer get that thing outside in dappled shade at first gradually over weeks moving to a more sunny location. Perhaps repotting in a more porous medium. One has to watch watering much more in full sun than in dappled shade, so if the OP doesn't have a lot of experience with watering citrus, it might be best to err on the side of more shade. Regardless, the higher light levels and humidity outdoors (depending on where the OP lives) should get this plant moving again. Once you see new growth beginning, then might be a good time to trim back the longest branches.

Anyway, that is what I would do.

I would CUT IT BACK so that the only few healthy roots you do have don't try to support the growth on top and then collapses..The reason many get die back and twig death is because a weak root system which CAN NOT support the top growth! If you cut it back, the plant will use what ever energy is left of its healthy roots and focus on producing more, while they take a rest from pushing out more energy to support the top..

You can't support or make big muscles with little protein , water or nutrients..You can not support a leaf canopy without nutrients and moisture either which your roots are not capable of providing, assuming there is a problem with the roots.

Many people have it all backwards...It's healthy roots that need to be there to support a plant needs..The bigger the health root ball, the more leaves it will support.

Why do you think I tree goes into dormancy when daylight gets shorter and temps grow colder? How can any tree survive without it's leaves or come back after being stripped off from a storm? There are NO leaves and yet the roots bring them back. Think about it. When a disease attacks the roots, drought, a hard transplant , root pruning, ,disturbance, overwatering and other factors, what happens to the top of any tree?

Like Dave said, it has very little leaves and it will not take up moisture as it is suppose too so yea I would definitely watch my soil and watering habits...If you want that tree to make it, it's important to give it a heck of a lot of sunlight and warmth, or artificial light like many are doing here..If you mix is still staying wet far too long, then I would find a way to make that mix dry out much faster by wicking it out or ' down pot' as Pip says into a better mix if it seems the roots are much smaller than you thought.

Thank you for all of your advice! I have not had a chance to do check the roots yet but I did just cut back the branches
(mainly only those without leaves at this point). I'm going to use the 5-1-1 soil mix and fertilize a bit. I'm in zone 7b. It's fall here but I did move it to the south-facing windows and will see how the winter goes. Thank you all so much - this forum is a complete fount of helpful gardening info!!