what type of potting medium are you using? have you checked the moist with a moisture meter or bamboo skewer?

maybe pull it out of the pot and see if the potting medium is soggy.

Have you checked for spider mites?

Sometimes the stippling causes a dullness to the leaves.

Josh

No spider mites that I can determine. It's in the same potting medium it's been in for the past three years, so the sudden yellowing is a surprise. I think I may have to get it out of the pot and look at the roots. The pot is very heavy and I'll need help, but maybe that would be the best way to go. I was thinking about some high nitrogen fertilizer since all the leaves are light green - any thoughts on this?
Thanks for the feedback - I really appreciate it!!

Have you by any chance noticed that it is taking longer for your mix to dry out recently?

This is a classic symptom of a collapsed mix thereby subjecting the roots to extreme danger, due to the fact they can no longer take up moisture like they are suppose too. They will also find it difficult to take up nutrients causing a host of problems.

Now with these extremely hot days, I would move it out of the sun if you even see the slightest bit of leaf curl due to dehydration.

Good luck

Mike:-)

Have all the leaves lost a little bit of green since putting it outside? If so it is probably what Mike said. They look pretty good to me, but sometimes without before and after pictures it can be hard to tell.

Otherwise, has there been a flush since putting it outside while the majority of existing leaves retained their color? That could mean nutrient deficient chlorosis, which can be caused by soil solution collapse as Mike said, or simply by lack of soil nutrients for new growth. Sometimes trees will pull nutrients from old growth for new growth, such as a Mg deficiency, while sometimes it's the new growth will exhibit the deficiencies, such as Zn deficiency.

My guess is if it's only the old leaves as you said, and everything else is green and healthy, it's a Mg deficiency. If the leaves are yellowing in general, it could be a soil problem or a Nitrogen problem.

Here's an excellent resources with pictures and descriptions of the various nutrient deficiencies. The extension website has dozens of citrus articles that are also helpful. 2.5 cents.

Here is a link that might be useful: A Guide to Citrus Nutritional Deficiency and Toxicity Identification

Thank you windy3 and meyer mike! I haven't noticed if it's taking longer for the mix to dry out. It's a little bit hard to tell because I had a watering routine when it was in the greenhouse - which was hotter and dryer than outside. We're in Seattle, so there is no such thing as hot weather - at least not so far & we've had intermittent rain. I should have included a pic of my other Meyer to show the difference in the leaves. My original tree is definitely paler (yellower) all over by about two shades. I was reluctant to stress it any further by trying to take it out of the pot, but maybe I will have to. There was not much of a flush of new growth - unlike his/her fellow citrus - this spring/summer, and the older bigger interior and lower leaves are the ones that are dropping. The new ones are discolored. Thank you for the link! This is really stressing me out, as I've had this tree for 7-8 years and have never seen it heading in a bad direction like this. Thanks again!

Before you re-pot, you should probably just check the moisture level. I had one of my 2 year-olds start yellowing two weeks or so ago, and thought it was my soil. The moisture was identical to my other soils, and I pushed some around to find the soil in good shape. I added some additional fertilizer to my daily watering to supplement the existing slow release fertilizer in the soil, and it quickly picked right up. New leaves were green and the older leaves started looking better. For whatever reason, the fertilizer I added to that pot just wasn't doing it.

You'd think if one out of four or five containers was bad it couldn't be the fertilizer, since theoretically you used the identical regimen in each container, but who knows. Maybe that tree 'ate' more food than the others? Maybe the watering washed more fertilizer out than normal? Maybe when I just didn't add enough fertilizer to that container to begin with.

Anyway, food for thought.

Hello Westgirl:

Windy is giving you some great pointers. Try them out and see what happens.
Also, as you can tell Windy is asking you seem very good questions that could relate to your problem.

The fact that you said it is drying out no slower than before is a good sign.

Windy has had good success with hers too and from all our heads around here, you will get to the bottom of it. I noticed on a picture this morning that the very new growth looks ok and that is a good sign. Just as soon as any branch should die with loss of leaves, then you definitely have to watch your moisture levels and the mix.

Mike

One more thing:

Please keep in mind what Josh said. It is possible that one tree is being attacked by a pest of some sort. Make sure you check over the whole tree, especially under the leaves and in the crevices, paying particular attention to very minute mites that you can barely see even with a magnifying glass, which is something I would invest in.

Even this handy tool will be an other life saver, trust me.

Mike

update - I pulled it out of the pot last night, and the roots look fine (although it was pretty dry). Since I've already done that I'm going to add some new mix since it's been in the same potting mix about 5 years. I perused the link that Windy sent and I think it might be phosporous deficiency caused by leaching - older yellowing leaves and bronzey new foliage - which could make sense considering it was watered a lot in the greenhouse, and has received a fair amount of rain since it's been out. Also, soil acidity can decrease P, and I gave it orchid fertilizer, to which it did not respond well. I was just looking for a water soluble high P fertilizer, as I'm a little bit leery of adding bone meal (what if P isn't the problem?)
Any further thoughts much appreciated and thanks again for your input, it's been very helpful!

West:

It won't hurt to fertilize now and try using vinegar in your water for next few few waterings.

If this is pH induced, your leaves will green up quite considerably. I wouldn't add singular elements until you first make sure you fertilize with a good rounded out fertilizer and vinegar in your water.

Windy has definitely linked you good information. Just make sure you make everything in a good fertilizer available first, now that you believe that over watering is not the issue.

Let us know what you do and how it goes. Remember too that making sure to count out pests is always a plus.

Since you are sure the roots look ok and it is not root rot, water, fertiliz and use vinegar asap.

Good luck

Mike

I very strongly doubt that your tree has a phosphorous deficiency. I have NEVER heard of a phosphorous deficiency in container citrus, when it is regularly fertilized with a NPK fertilizer. Phosphorous does not leach from a container, as does nitrogen and potassium. Nitrogen and potassium are both VERY water soluble and readily leach with every watering, but not phosphorus. All of the leaves that are turning yellow, and dropping are the older leaves on the tree. Your tree is withdrawing the nitrogen from the leaves (thus they are yellowing) to reuse in other part of the tree before discarding them. When a leaf no longer is capable of supplying its expected quota of energy to the tree, it is quickly discarded. There is no welfare program for citrus leaves. However, your tree is also under fed. If the tree's problem was other than aged leaves, you would be seeing yellow dropped leaves from the new leaves also. Also it is not wise to add this and that chemical in hopes of coming across a cure. First ascertain what the problem actually is then correct it. I'm sure it was also not helpful to the tree to let it remain in the same container and "soil" for 5 years. Fertilize the tree using a high nitrogen fertilizer. You can add vinegar if you wish, but there are much better ways to acidify. Organic acids such as vinegar, have an extremely short life.

Thanks all. I repotted (no, it wasn't in soil to begin with) and it's been spectacularly unhappy ever since - but we did just have two days of rain, so I think it's probably for now, just too wet. I added fertilizer when re-potting, so I hope it will start to benefit. For now, I'm leaving the poor thing alone with it's new mix & fert, and hoping for the best. I think I'll test the ph of the soil next - and proceed from there. Very informative and helpful comments - much appreciated!

Hi Westgirl.

It is not the pH of the soil at the time of testing that will be the most important, but it is the pH of the water solution you regularly water with that is.

We are talking about a containerized tree

Mike

Update: I repotted a couple about 10 days ago and the only improvement I've seen is that the tree has stopped dropping leaves, but it still looks terrible. Also, the potting mix that I used - basically 5-1-1 - seems too wet. I've only watered twice since I've repotted, and have included a high nitrogen liquid fertilizer. I'm wondering if it's too wet? All the fruit turned yellow quickly, but is not viable. Should I remove the fruit? Any suggestions on how to hasten (or make sure of) recovery? I'm so worried!! Trying to be patient, and refrain from pulling it out of the pot again, and starting over. I've included some photos. Thanks in advance for any advice!!

Here is a link that might be useful: still suffering meyer

Westgirl:

Sometimes it can take up to over a year before any vast improvement on certain citrus container trees. The branches look ok, which is very important, and I would take off all the fruit while it tries to recover.
Expanded energy will go towards repairing roots depending on much damage there is which can take quite awhile. It will recover as long as you make sure you do all you can to keep the roots happy!

I have a few trees my sister gave me in horrible condition at the beginning of spring, and despite all my good cultural habits, none of them have improved in appearance just yet, but some are finally getting a few new leaves. I will take pics real soon to show you.
Don't fret, just be patient and they will respond to your goodness.
Are those buds I see?

The mix looks ok by the way. Your tree is not taking up moisture quick enough because of its condition, that is all.

Mike:-)

Thank you Mike - I just went out in the dark and removed all the lemons that I could see - 16, which hurt my heart, but if it helps the tree, it will be well worth it. I will be patient. What do you think about foliar fertilizer? Or should I really just be calm and let it recuperate at it's own speed? (which reminds me, I hope your heel is recuperating too!)

According to this site, bronzing of the leaves can be a symptom of magnesium deficiency.

Here is a link that might be useful: Macronutrient Deficiencies