Patrick,

I can't say what the problem is regarding the leaves, since the yellow leaves simply could be old leaves destined soon to drop, and curled leaves could be caused by too little water.

The big question is this: does the lemon really need to be repotted? Unless the tree really is potbound, with roots really crowded in and growing around the container, I would wait to repot. Most nursery stock, if in good shape, should not require immediate repotting. Unless it really does need a new larger container, give your lemon a few months to acclimate, and then consider repotting later in the spring when I assume you will be putting it, with its container, outside for the season.

Don

I was concerned about possible root rot due to being overwatered vs being potbound. Despite some yellow/curled leaves, the plant seems to be stable and even starting some new growth. Since it seems to be doing ok I will leave it alone at this point. Thank you Don for your response and helping to discourage me from doing the hasty repot.
-Patrick

No worries, Patrick.

Just watch it closely, since if it is close to being rootbound, the new growth up above may be mirrored by new growth below, and that may kick it into the rootbound category. As a rule of thumb, I find that the citrus I've had that are getting rootbound, once they go into flowering or a growth cycle, will need watering seemingly every day, but definitely every two or three days in the winter. Outside, in the summer heat, I actually set up a drip irrigation system and water for 45 minutes five to seven days a week up here in Connecticut during the July-August heat.

I can leave the citrus alone for a month or more with this setup, since overwatering (as when I'm away and mother nature provides a week or two of additional water in the form of daily rains) is not as much of an issue during the summer. Underwatering, however, can have terrible effects! I once came back from a trip to England to discover that my trees were dropping all their leaves: the water pressure in the main feeder line had dropped (due to summer watering demand in the neighborhood, I think), and half the drip-emitters were no longer dripping at all, and the rest were taking their time about it! I arrived just in time, and did not lose a single plant.

Don

Don -

I thought I was overwatering then I stopped and now Im not sure if Im underwatering.

They say if the top two inches are dry then it needs water, but when I water, it doesn't drain to the bottom. the soil is fairly compact - i can't stick my finger two inches into the soil...

The tree dropped all of its leaves and some branches are turning brownish black.

How do you know by the leaves or tree that its over or under watered? Both seem to cause leaf drop....