The worst thing to do when a tree is loosing all it's leaves is to fertilize. at least in my case.
What nutrients will a tree take up without leaves to work with roots?

I would be more concerned about either spider mites or unhappy roots.

Have you check for spider mites yet with a magnifying glass under the leaves? By this time of the year, you might have some.
Have you lifted the plant from your pot to see what the soil mix looks like or the roots?

What do the leaves look like that fall off?
What color are they when they do?
Are you loosing branches or twigs too?
Can you provide us a picture?

Have a good night.

Mike

I will see if I can get a picture posted on here some time tonight. I have not checked for spider mites yet, but I do not think that would be an issue, haven't seen any evidence of that. On to your other questions-

When the leaves fall off they look perfectly fine; green, no brown or black marks.

As the leaves fall off leaving the branches completely barren, I do have some branches dying off.

It is easy to stop winter leaf drop problems quickly just by heating the root system, or removing the foliage out of the direct sun. Many people place their trees in a room where the tree's foliage will receive as much sun as possible. When they do so usually the container is either below the window level, or in some other manner out of the direct sun shine. The tree's foliage heats up, but the roots cannot. A citrus tree is a single unit, so when there is a change to one part of the tree, an equal change must be made to the other part of the tree. The foliage, and the root system are both of equal importance when it comes to the survival of the tree. When the roots aren't receiving the needed and proper care, the foliage will surely begin to fail. When the tree's foliage is receiving direct sun the root must be at a temperature between 64 to 70F. If the roots are not, then the foliage must be kept out of the direct sun. With a winter growth program of 70F for the root system, and sunlight, or artificial light, for the foliage, the tree will not lose its leaves, a problem called "Winter Leaf Drop". Plus the tree will normally put fourth 3 - 4 new growth flushes each year. A tree's potting soil will be colder then the room temperature, due to evaporation from the container's surface, plus the containers side walls if the tree in in a terra cotta container. Therefore, never rely on the temperature of the room as being the temperature of the root system. - Silica

Hmmm, Silica you have given me something to think hard about. I am posting the picture here as Mike requested. I have checked for mites and found no evidence of them. Hopefully, you guys will notice something from the photo, I'm pretty new to gardening, but very new to citrus, so I apologize for the naivete.

How much water would you recommend? Usually I water it with about 12-13 oz weekly.

Silica- if you do determine that the problem is the roots being out of the sun (they are), how do I heat them?

Fwiw: this picture does not show my dwarf orange tree, which looks great and is at the same height (aka the roots are out of the sun). It is situated slightly to the left.

This post was edited by Soulfire on Wed, Jan 30, 13 at 22:17

Btw, Mike I was looking at another post where you have pictures of your trees. They're so green! Beautiful!

Thank you Soulfire:-)

I wish the same for yours too!

Mike

Mike, were you able to see anything from this picture? It was taken in the evening, the room gets much more light than this. Do you think a wider pot would solve this problem?

Recently had the issue that silica is referring to with my key lime tree. I have 4 citrus trees in a sunroom and only the lime was dropping (perfectly green) leaves, the other trees were fine. Got suspicious because the key lime is by far the least cold tolerant of the bunch. I took a chance and put a small heater in my sunroom ( it was running about 58 degrees in there, fine for most citrus, but I took it up to 65) and the leaf drop stopped quickly. I was also storing water in there and it was next to the door...it was even colder and I was watering with it! I moved the water to the kitchen. Since the heater, I added a little more humidity to the area and the soils dry a bit faster as well, so I water a little more often. BTW, the ceramic container was in full sun just as the leaves were, but the air and ceramic were cold!

I'm wondering if that could be it. The thing is, the trees are actually in my bedroom as it is the brightest room in the house. Temperature should generally be low 70's upper 60's. I can't imagine it getting lower than 65 at night, even on the coldest nights. Is that still a problem?

Soulfire...

I don't want to disagree with anyone but I do have my own feelings about your tree.

I think your temps are much warm enough to make any citrus in a pot grow in full sun and in fact just right.
You would have to be living in a very cold room, minus 60 or leaving your trees on a VERY cold window sill, but then the pot would be in the sun and warm up anyway by the a.m

Most of my trees are set on the floor in a room that gets no higher than the 60 dgrees in there and all are in a very sunny room facing south windows and I never have this kind of leaf drop or branch die back.
Now if I added suplimental lighting carrying light over for more than 12 hours on plants with cool roots, then I would.
The sun alone is not the issue for mine. The fact that your other tree is doing just fine should be a dead give away:-)

As I said on the onset, I think it's root rot or pest's.
When the roots are not happy then the plant is not, and roots being the heart of your plants.

Did you check the roots, the mix, and how long before it dries out?

Suffocating roots and lack of airmovement around the root zone, salt toxicity, mixes that stay moist far too long at this time of the year, and fertilizing while your roots are dying are all what adds up to what you see. Your mix to me even from this far does not look good.

Let's not forget too under and over watering.

I would check the roots, monitor your mix and moisture, and hold back on fertilizer until you know their is good active growth. I'll bet if you had your tree groing in a much more open aerated mix, you would not have this problem:-)

Mike

This post was edited by meyermike_1micha on Fri, Feb 1, 13 at 12:48

Have to agree, if your room is upper 60�s - low 70�s then temperature is unlikely to be the problem. I was thinking this direction because of the leaves dropping without turning yelliow or brown first, but there are other possibilities...if possible start with checking those roots and report back, Mike is trying to narrow down the problem with you...

Mandarin, how's your trees these days? Are they holding up ok indoors? Mine's are starting to bud all over the place.

Soulfire..Has the leaf drop stopped? Have you figured out what is going on yet?
Dead branches that look like that always stems back to too much moisture in which fine roots can not handle, salt deposits, and or suffocation.
I wish your tree well.

Mike

My trees are blooming and growing, and no more leaf drop! Been hanging around this forum off and on for a few years now, my trees are still a work in progress but I keep learning. I actually got so frustrated with getting insects and losing leaves in the fall (when bringing my trees indoors) that last year, as an experiment, I left them in the sunroom and never put them outside! Got mites anyhow ( no scale though, and no leaf drop) but now using the rosemary oil, I'll try putting the trees outside again this year. Well, maybe except for the Meiwa kumquat, it's doing so great indoors and it's unexpectedly become a favorite ( shhh, don't tell the others!). This year's goal is to learn how to post pictures...

Well, I removed the tree from that pot and added a bunch of soil, then placed it back in and watered it a bit. That was yesterday. The leaves are still dropping as of today, although I'd imagine an immediate stop of leaf drop isn't realistic. I didn't change the mix, although I have stopped fertilizing it as of about a week ago. I'm hoping that giving the roots more room to breathe will help. I'd rather not buy a wider pot and totally change the mix when it is so weak. Another week or so of leaf drop and there's going to be nothing left. Any other suggestions or how long I need to wait to know if adding all that soil worked?

Also, if it does lose all of it's leaves, does this mean the plant is dead or just dormant? Would there be a point to still watering it occasionally in the hope that when I put it outside in the spring it grows back?

*UPDATE*- I have begun seeing little webs on a few leaves, I think we've narrowed it down gentlemen. I sprayed it real well with a water/canola oil/baking soda mix tonight.

This post was edited by Soulfire on Tue, Feb 5, 13 at 20:16

Soulfire...That is why I suggested you use a magnifying glass. Because by the time you seem them with the naked eye, it's usually too late and many of your leaves will have fallen off.

As I said, usually a weak plant is soul food for mite. The two usually go hand and hand.
It's important that you keep your tree in a very good porous mix, or at least trick the moisture into leaving your pot by placing a wick at the bottom of the pot of placing your potted plant into a much bigger pot filled with mulch right on top so the the mulch will wick away the moisture form the inside of teh pot your tree is in. Get it?

You are doing good:-)

Ok, I will not say for sure that Rosemary oil will kill your mites, but it has certainly taken care of mines right off the bat!

Thanks for the update and keep a close eye on the tree next to it. Mites have a tendency to spread to other plants.

Mike

Also, if it does lose all of it's leaves, does this mean the plant is dead or just dormant? Would there be a point to still watering it occasionally in the hope that when I put it outside in the spring it grows back?

It can be common for trees to loose all their leaves if under stress, some sort of shock, or even root rot.
You can be sure it's alive if you scratch the bark and it's green.

Citrus do not go completely dormant. I would call it sort of a suspended animation until you provide more light and heat.
The more light and warmth = sped up growth
Less light and colder = slowed to almost no growth.

As long as your branches are alive, it's a good chance it will show good growth once you give it what it needs.

Mike:-)