Hey, welcome here and another scientist...What's up with that?

It seems you have done your homework and even gave us some great detail...

Let me ask, instead of what is going on now, what about the spring and summer? How did it look then? Nice and green? Was in actively growing? Did you feed it all summer? Did it have bugs then? Is any of that growth from the summer ? Did it get full or part sun? Have you ever left it in temps below 55 degrees?

Glad to have met you. You are right, many will help you out?

My guess is that it still has time to adjust to the new lightning and it's very difficult to keep the leaves lush and green without true sunlight and lots of fertilizer...The warm days of summer basically...In our weather it's very difficult to get them to grow to their full potential, perfectly green full and void of pests, but possible..If your tree shows no sign of twig or branch die back, I would not be too concerned until you can put it back outside again come spring)

Welcome Jay! One of my Meyer lemon trees has leaves like that. Question: are the leaves on the bottom left older leaves? I am no expert, but that looks like a previous Mg deficiency. I'll post photos of my tree in a bit. I agree with Mike in that it just may be stress from being indoors and it should adapt. You e done everything right. If those in fact are older leaves, the may stay like that regardless of what you do. The important thing is how does the new growth look? If THAT is healthy, then I would not worry too much.

Oh and it's great to have another scientist and statistician on board ;-)

Here you go...

Thanks Mike and Laura, great to meet you both. Have been reading your posts for a long time now!

Mike, to answer your question, the tree was as green as can be over the summer, and nearly doubled in leaf count. It's small enough I can still do that ;)

I didn't notice any bugs, and yes, it was in full sun. The yellowing leaves I am referring to did indeed grow over the summer which is answering part of Laura's question. This is why I was concerned. I have seen some of the older leaves yellow and fall, but this is newer growth.

You've got me thinking...I did have the tree under a single weak LED bulb for a month before I got the t5 HO setup. That may have set current events in motion (inadequate light)? The branch with the yellowing leaves was also the hardest hit by scale.

The tree is actually putting out some new leaves (very slowly of course). Perhaps if those leaves look normal in coloration there is not much to worry about? This is the general theme I am taking from both of your answers.

Thanks again!

-Jay

Also: if I wanted to correct for Mg deficiency, how much Mg sulfate would you suggest to add to a 1 gal FP solution?

Jay, I think I'd start with 1 tsp/gallon of warm water. I have a blood orange that has some leaves like that also. If I remember correctly, Silica said that Mg and Mn deficiencies look identical except that Mn deficiencies occur in new leaves and Mg in old. My blood orange has it in newer leaves. I recently gave all my trees this via the roots and then VI's foliar spray...I hope it helps.

Laura, hey))

What I can tell you Jay is that if you were fertilizing with Foliage Pro weekly or weakly every week without let up, warm temps above 55 at all times and using vinegar in your solution often, you should of had rich green leaves...The Foliage Pro lacks nothing and the vinegar helps your trees take up nutrients if the pH of your watering solution should get a bit high to lock nutrients...

Laura you've been doing a fantastic job with her trees as we can tell...On average, most are richly green and growing robustly even now!

What I can tell you from years of growing them is that unstable temps, a change of lighting, less sunlight , cool temps below 55 and over watering can cause what Jay has and these conditions usually correct themselves during the summertime..

Some leaves will revert to green while others will stay yellow like that and eventually fall off...

What I do always is make sure if I am fertilizing, to provide as much artificial light or sunlight in any south facing window on the window sill. or in a greenhouse as possible to correct those issues..If I am going to provide anything less, then I try and not worry about it until they can go back outside again....

My highest priority is to watch my watering schedule and to make sure they are pest free because they will not have the vitality like they do in summer and are prone to pests in this state without beneficial pests..So these two are my most concerns and everything comes after if I have the time or think of it...It's been working great for me every year and I have yet to loose a tree...I wish I could keep them richly green all year, but 3 months out of four is quite difficult unless you can provide the perfect conditions during them times too....

Jay, you said that they grew as green as they could all summer and that they doubled..That tells me your fertilizer worked and the weather was in your favor..Somewhere along the line either your tree was exposed to cool temps, a lack of fertilizer, not enough vinegar of all three...Did you apply a 'slow release' fertilizer in your mix? Have you ever accidentally forgot to water it? It looks pretty dry from here...Do you use tap water, lots of it, all summer too, or rain water.....???

Laura, if that stuff works, please let me know. I would like to think it's not a systemic problem going on verses topical...I have that stuff too I bought years ago and never used it. I might as my trees come out of winter growth to speed things up...Thanks