This seems a fairly common syndrome of large red oaks but I'm not aware of what is causing it. A couple trees in my neighborhood have been cut down in the past 5 years after similar looking dieback. Any ideas? I'm pretty sure white oaks and cerris oaks are not having the same issue...right?

Ken, The problem with this particular plum tree is twofold: (1) it belongs to the co-op, not to me, and I don't think they'd take kindly to me cutting it down and (2) it's right in the middle of my HOSTA GARDEN, providing the main shade for it. The hosta garden gets the late afternoon sun, it's an eastern exposure, and the oak trees behind the plum tree (oak trees are in the strip between the sidewalk and the street) gradually shade over everything. Various neighbors have told me that, when they inquired about having a dead or dying tree replaced, they were told that the tree would not be replaced. So, if this plum tree up and dies, I suppose they will saw it down and leave my hosta garden to be shaded only by the oak trees in the late afternoon. I wonder how that will affect my hosta garden...

Ficus benjamina normally drop their leaves at any change of physical location, even from room to room indoors. Likely the foliage will all grow back and you will very much come to regret planting it in the ground, as it buckles any pavement within 25 feet and sucks all the water away from any plant growing nearby with its aggressive, invasive surface roots. Here is a link that might be useful: thread on F. benjamina, if that is what you have

My humblest apologies for my long posts. The firmness of the roots is a good thing. Be wary of disturbing the actual root mass unnecessarily--it just may cause more damage. I know someone who bare-roots her trees every time there may be a problem, and I've been doing my best to discourage this process (ahem. you know who you are ;) Ultimately and ideally, in a potted tree, you do want lots of fine roots for nutrient uptake as opposed to woody lignified roots taking up space, but if the roots are so fragile they are breaking off essentially spontaneously, then they are not viable anyway. pH does seem to be one of those topics that sets some people off for an unclear reason, but I now fall into to the camp of I-don't-really-care-about-it. pH management in *containerized* soils is different from the earth and the reason it is a PIA IMHO is b/c it is extremely dynamic. (Out of curiosity, what is your method for checking--is it pH paper or a meter?) Having said that, citrus do prefer a *slightly* acidififed soil, but they are not blueberries. Most tap water is going to be basic to some degree to keep contaminants from precipitating out, but since you've used bagged soil, there is a very high likelihood that there is a good portion of peat moss in your mix and therefore you've already got a slightly acidified soil. I'd leave that alone for now. Otherwise, you can add a light dose of slow-release fertilizer that is nitrogen-dominant, and since many sources of nitrogen are acidifying on their own that may help. Also, I've seen a brand of those slow-release granules that also has sulfur in it, and that might help over time. When you do fertilize otherwise, you can choose an acidifying formula that way too (I use Miracid for the most part). No, thorns do not *precede* growth. They *accompany* it and you should be seeing something besides just thorns if you really do have some sort of growth. Other possibilities are thorns that you missed previously since there were more leaves to cover then, actual new vegetative growth forming (doubtful if you're still seeing signs of decline like continued leaf loss), or the beginnings of massive pathologic stress-bloom. You're going to have to wait awhile before you see results--I had a tree in CHCs (stupidly) for over a year before I pulled that sucker out and rehabbed it, and it was easily 5 mos or so before I felt like I had made any progress with it whatsoever. The tree's stored energy is eseentially depleted and it has to have time to build that back up. Which is hard when it doesn't have many funtional roots and reduced leaf surface area. Something some speak of, but I don't do, is to prune it back significantly and reduce the canopy mass when you have had major root damage. The main reason I find this difficult is that often leaves will drop first from the inside of the canopy in this situation (older leaves), and then if you prune it back you're cutting off the rest of the leaves--shooting self in the foot while you're at it, lol. The tree needs maximal photosythetic area. Personally, I think citrus is hard to kill if you've got the basics down. It's easy for them to get into trouble, but I don't think they actually die that easily from stuff like this. So it's reasonable to keep trying with this tree. Branch dieback will be your guide, but even if the graft goes, the rootstock can survive--and then in a little while you have someplace where you can do your own grafting. How appropriate--lemonade out of lemons. Literally. Please keep us updated on your progress. Hopefully someone else will comment--where is tapla, bencelest, eyeckr, jackpines, citrusboy? Surely you gents can help us out here...oh wait, I know where they are--they're sick of my longwinded posts :)