This is really an exercise in futility after you have already thrown it away; without photos; and without knowing so many things, such as the rootstock it was on, the soil type and any soil pathogens that might have attacked your roots, such as phytophera or nematodes. If you weren't careful in transplanting, you may have lost a part of the rootball, which would require some time to recover. If you are going to replace it with another Meyer, put it in the ground right away and don't fertilize it for at least 3 weeks; or until you see a growth spurt; the absence of fertility encourages the roots to grow seeking food and water. If you buy your tree from a reputable grower, they will give you growing instructions. A Meyer planted in the ground in zone 9 CA is really a pretty easy tree to care for.

I'm posing this question to know what to do with the next tree I buy. You asked some pretty sophisticated questions, and I don't know even if I still had the plant if I could answer. I do know it did not have nematodes. It's possible that I didn't get all the root ball when transplanting, I suppose. This was my first Lemon tree, and I have heard they are pretty easy keepers but of course that has not been my actual experience.

The other issue is light conditions; if you significantly change the light conditions of a Meyer, it will drop leaves
So, if you lost some of the root, changed the light conditions, and also fertilized it on transplanting, your tree got a triple whammy from which it likely would have recovered, but it would have taken several months.

Before you plant another tree in the same place, you should know the rootstock of the tree, the pH of your soil, the pH of your water; and you should apply John's Rule of Thumb... to do that you hold up your thumb at arm's length in front of you; now turn 360 degrees, full circle. Do you see any other trees like the one you want to plant? If not, there well may be a reason that no one is growing it there.

Well, if you're in California, it is unlikely it's nematodes, we really don't have nematode issues here. But, without seeing the tree, John is right, it is simply speculation on our part. It could be many different things. First, we need to know where you live. Secondly, we need to know what kind of soil you have. I'm going to make some assumptions here, but, guessing you are from S. California. And, possibly on clay. If you watered every other day, especially if you deep watered, you simply suffocated your tree by drowning. If you're on better draining soil, then more likely it was overgrowth of phytophthora (Foot Rot), which is soil pathogen that will proliferate in the right conditions (wet soils, temps from 55-65 degrees, our typical temps during winter/late spring). If you have gotten to us sooner with photos of your tree, we might have been able to turn things around. Citrus don't need to be watered that frequently. You want the soil to be moist about 18" down. If it starts to dry out, then you water. Water deeply enough to get the water down 18 to 24", where the feeder roots reside. You should check your soil to see whether or not you actually need to water. Don't just water randomly. If you have clay, you should be planting your citrus trees on mounds to improve drainage. If you're in California, your soil pH is just fine, no need to mess around with soil pH, which is temporary at best. Lemon trees thrive in S. California, but ;you do have to follow some basic good gardening principles.

Patty S.

Well, if you're in California, it is unlikely it's nematodes, we really don't have nematode issues here....

Patty, wherever did you get that idea? Nematodes are a big problem in much of the Central Valley; and in a wide variety of crops, including citrus root knot nematode.