Bone dry. No wonder it's looking that bad. Good luck.

Usually this is how a tree looks when there is a lack of water.

Too small photos - I can't see what's with the roots.

Perhaps the roots are overheated in the sun and boiled.

You can try to revive the tree as it is.

Pluck fruits, put in the shade, spray with water, remove rotten roots, soil - peat with perlite 1:1, water sparingly.

Hot temps + hot sun = dehydrated leaves and fruits. I'm guessing this tree was indoors at the place where you bought it ? It probably wasn't used to being outdoors. Do what Alex said, and good luck.

I agree with everyone else that the tree looks dried out. If the soil was more clay, the clay could have hardened around the roots so that the soil in the pot appeared wet, while the mass of the rootball is dry. Personally, I would soak the rootball until that clay loosened, then remove as much as I can and repot into a looser medium. Expect lost leaves and some dieback. As long as the branches haven't dried out, you still might be able to save the tree.

Water deeply not sparingly. Make sure it never dries out completely especially in your heat and do not water in sips. Soak the pot under water if you decide not to change the mix out and let it absorb the moisture.. If you change the mix make sure to remove all the bad stuff from the root zone while you hold that root ball under water.

That is the proper way to water especially in such a fine mix that holds salts.

Thanks a lot for your help!

Following your advice, I plucked the fruits and dipped the root ball in warm water for 20 min and tried to wash off as much clay and dead roots as possible. The previous soil was really just compacted mud. I have not dealt with root rot before but it didn't look like the roots where dead or rotting, not black or foul smelling, still holding together strongly and not rotting away. However they don't seem as bright as I've seen in other pictures so i don't know. Pics attached below.

New soil is much lighter, and I believe a peat and perlite mix.

I'm surprised a healthy lemon tree would react so poorly to being under full sun for a few hours everyday over a 3 day period when I was still watering it half a liter daily, then almost 2 liters everyday for 2,3 days when in the shade, and then stopped fearing overwatering for the following 4 days until now when the soil was finally getting drier, the soil was always moist, at least on the outside.

I hope it can recover from the water stress and the successive repotting. Branches don't seem to dry, hopefully it can bounce back.

If you have any more tip, they would be very appreciated. Thanks !

To answer a question, I bought the tree in a shop where it was left outside in a pretty shaded area, I'm not sure how much direct sun it was getting, if any, or how much water they were giving (they said every day, but didn't specify an amount).

Which makes me wonder how much I should water now ? I've put roughly 1 liter after the repotting to wet the new soil, and the roots were coming off the dip. Do you have an idea of an appropriate amount ? Should I mist considering the high temperature and humidity ?

Thanks folks!

Alex, in response to your comment about a healthy tree reacting so poorly, sometimes the heat and light of direct sunlight if the plant is in shade can stress the tree, and you'll see some leaf drop. More likely, and my best guess on, what happened, (especially if it was in dense soil), is that the root ball dried out and the clay hardened. Then, when you watered the tree, most of the water ran over the sides of the pot and not through the rootball. Take a lump of clay and let it dry in the sun, then pour a bunch of water over it and break it. You'll notice that the water doesn't really penetrate the clay. The same thing happens with houseplants when they get too dry, the soil becomes hydrophobic and water runs over the surface of the soil without reaching the roots. It's why it's important to soak a plant that's gotten too dry. More than likely the clay hardened, the roots got dry, and then the heat dried out the leaves. Still possible to save a tree like that.

Just as we have to protect our trees in the winter cold , you have to protect your trees in the stifling heat. No plants in a pot actively growing that I grow can take the extremes of either cold or heat. I even protect most of my plants from extreme hot sun and I live in New England. They would croak if I left them exposed to severe heat day in and out.

Hello Everyone.

Its a month later without any change and then all of the sudden a bunch of fresh leaves sprouted at the base of the stem:

Very glad I didn't throw it away, but I am wondering how to take care of it now ?

I've cleared the dead leaves and branches on top and I keep the soil moist and keep the watering to a minimum (once every 2 weeks, it's still 80%+ humidity here).

Any advice at this stage ? Should I prune more ? fertilize ? Keep water to a minimum ?

Thanks again for all your help.

Alex

At this stage I would leave the tree alone. Keep the soil moist (not overly wet) and wait to see if the tree begins to reproduce new foliage. It could be up to a couple week to a month.

Do you know if the tree was grafted, seed grown or a cutting? If it was seed grown or a cutting, then your tree is growing back. If it's grafted, then I would make sure new growth is coming from above the graft line. Trees can come back from a lot, and total defoliation is not always a death sentence. As long as some part of your tree is still alive, it can grow back. If it were me, at this point, I would just keep doing what you're doing, try to water less on a schedule and more by when the soil is more dry, but I tend to go with a philosophy of if it isn't broken, don't fix it. Then fertilize once the leaves and growth are a bit bigger.

A tree in that condition that then sends out new growth from real low like that is probably growing from the rootstock. If you give a better pic zoomed in towards the new growth and a few inches above and below it we may be able to see if it is rootstock.

Hi. Take a close up view of all side bottom part. Curious if that’s the root stock or the grafted part coming back. The leaves look like the grafted portion. If so you are pretty lucky

looks like a rooted cutting.

I agree, no signs of a graft line on that pic, suspect a rooted cutting. Looks like persistence and proper care paid off!