Hello, So I turn to here after multiple attempts, numerous hours of reading on various different issues, trying to monitor, and still weeks of consistent leaf drop. Background: ~2 year old meyer sapling, bough tin Oct 2018 Kept in container entire life Live in San Francisco Bay Area, specific East Bay (Hayward). So no freeing temperatures Last winter, I kept the tree outside. Lost 60-80% of leaves due to signs of nitrogen deficiency Flourished Summer 2019, lots of growth Summer soil mix was drying very quickly (everyday), so remixed a slow draining soil and repotted. Brought inside this winter, initial great growth, then slow-ish consistent leaf drop for ~10 weeks Solutions tried: Bringing inside as I thought last year's nitrogen deficiency was due to dormant roots. Fertilizing tree occasionally Monitored soil temp, but showing ~60-70 F Gravel dish for humidity Grow light set for 12 hours originally, now 6, hours of light Watering only when soil is dry 2" deep I usually have such a green thumb and so my hubris has kept me from seeking help. But now I am desperate, I have never had such a persnickety plant! The final thing I should call out is that the new potting mix I concocted has been drying out very slowly indoors. Outdoors last summer, I was still watering every 2-4 days. But inside, it is taking my soil 2-3 weeks to dry out. Do I have root rot now? I am hesitant to pull the tree out and stress it anymore to inspect the roots!
Welcome to the forums. I would replant the tree into a porous mix as that is the preferred medium for citrus. It may mean more frequent watering but the tree will be happier for it. The current medium retains moisture for longer periods than desired, especially for indoor cultivation as you are finding out. Here are a few more thoughts I had: A tree should undergo a period of acclimatization before being moved indoors. Perhaps that had not been done and thus the leaf drop. A tree should be fertilized regularly while it's actively growing. During winter, if the tree is indoors, there's still some activity given the right conditions so I suggest fertilizing at half-strength. (I use a water soluble fertilizer.) Use your discretion. It's good that you monitor the soil temperature. Root activity slows at lower temperatures and ceases once in drops to 13C/55F. Leaf drop occurs when the tree is exposed to light when the roots are dormant or nearly so. The gravel dish probably has little effect in raising the humidity. A humidifier would be more effective. However I'm not convinced lower humidity levels would cause leaf drop in a Meyer lemon. The amount of supplemental lighting required depends on how much natural light there is. It may not be necessary at all if the tree is sitting behind an unobstructed window with a southern exposure. Root rot would cause the leaves and new growth to wilt and so it appears not to be the case. Nevertheless, does the container have drainage holes? What is the whiteish substance on the leaves and stems? I thought of mealybugs but I can't see any. Have you considered moving the tree back outside? I wonder if the leaf loss suffered in the first year was due to the tree having been raised in a greenhouse and not being acclimatized to the outdoors before the weather turned.
This whitish thing on the lower section of the stem seems like a salt deposit. I suspect too rich soil (too much fertilizer used). Or too dry air.
Thank you both (particularly @Junglekeeper) for the thoughtful replies! I apologize in my own delay in response. @Junglekeeper, to answer a few of your questions: Drainage: Glad to hear that the leaf drop isn't typical of root rot. Yes I drilled many holes into the bottom of the pot. White residue: spinosad for some leafminers that attacked at the end of the summer. I tried rinsing it off but it's hydrophobic, so I wiped it off the leaves as best I could. Moving outside: I haven't thought of that. Honestly that could be the case last year as there are many citrus trees in my neighborhood that do very well. Though they are much older/planted in the ground. It is too late now that it's spent half the winter inside? I will definitely take the advice to re-pot he plant again in a faster draining medium again. I do remember it doing very well despite the fact I was watering it almost everyday in the summer.
At this point I would move it back outside if there is a location where it would get some protection from the extremes of weather; there may be further shock to the tree otherwise now that it has spent some weeks inside. It's your call. Spring isn't that far away and the plant still has a good complement of leaves with almost no stem die back.
