Hi jenn, A couple years ago I planted 3 Meyer lemons in my front yard, and I too had read to plant the collar just above the soil level. From what I'd read, one does this so as to not develop rot at the trunk/root interface. Additionally, especially for those of us on clay soil, it is recommended to plant on a mound. Below are photos of one of my trees - immediately following planting, at 1 yr, and at present (just shy of 2 yrs.). Meyer lemon 3: Planted just above the horizontal soil level (you can see a bit of mounding that rises like a volcano from the surrounding soil level). Meyer lemon 3: 1 yr. after planting. You'll notice that the mounded soil around the trunk has fallen away exposing some thicker roots - not to worry, this is fine. I've also moved the mulching pebbles, expanding outwards. When I did this, I had to add a small amount of topsoil, but you'll see that it was at a level that NEVER covered those thicker base roots. Meyer lemon 3: 1 yr, 10 months after planting. You can definitely see some of the thicker roots exposed - these will continue to thicken over time. I've groomed the tree a bit by pruning the lower branches; the tree seems to want to grow more wide than tall at the moment. Tim

Citrus need their surface roots near the surface too.Its ok to mulch a tree in the ground with lawn clippings but always keep the trunk clear to reduce the chance of collar rot. All mixes sink over time...If it was me i would tip the barrels on their side and gently remove the tree from the barrel and inspect the state of the roots(should be light brown)...prune any dark.mushy or smelly roots and then prune the top relative to the bottom eg if you prune the roots lightly then prune the top lightly...If no prune,then no prune top..Take out old mix and refresh with new mix until you can put your tree back at its proper height with collar up and out of it(shallow rooters).I always pot to the brim and keep the plant high as the tree will compact a bit over the next few waterings...I find mine compress an inch over time which is perfect.....tease the outer roots out to encourage the roots to grow into the new mix and add some slow release fert....If the pot is rootbound and you want the tree to remain the same size..the above is recommended but if you want it to grow= a bigger pot 2 to 4 inches bigger than root ball will do the job(although a half wine barrel is pretty big already)...at the minimum for now= remove the soil from around the collar and let the air dry it out....when you mulch you should never have the mulch up against the trunk,leave a ring of freedom LOL

Thank you, I'll get mine in some soil later. My drive in shed I my riding mower in is doubling as a cold frame for some metasequoia seedlings but they're zone 5 tolerant. If the Lantana cutting grows too well for the kitchen I might move it to one of my garage windows. It's attached but not insulated or heated (except when I'm working on one of the cars). I'll pay attention to how low temps by the windows get in there.

Hair, I don't have first hand knowledge, but since the rootflare area isn't buried and the tree is growing towards the light, ( I am guessing) you are likely going to have a nice interesting growing trunked tree there, I would be happy if there is a bit of an interesting crook of growth of the tree VS plain ole straight up-ness.