Hmm don't know what would have caused that but citrus heal wounds very well, just leave it uncovered and let it dry itself out and scab over.

I started a similar thread recently if you are interested....

http://forums.gardenweb.com/discussions/3998239/new-arrivals-for-me-as-well-emergency-broken-branch-questions-below?n=26

I figured it was either heat, or root rot. I've got it potted in a 2:1 sand/compost mix. I also have a naval orange and Meyer lemon in this same mix and they seem to be doing fine. They're watered on average once per week and fertilized every other with foliage pro. the clementine tree leaves look fine, has a few leaves that are brown at the tip...not sure if this is related to the cracked trunk or not, but, doesn't seem to be getting worse. So I guess the question is what caused this/what can I do to fix it. I don't wanna lose my tree!

My first suggestion is to definitely change out the mix for all your trees. I prefer the 5-1-1, but others here like the gritty mix. Where do you live? Will it live outdoors all year or will you need to bring it in for winter? If so, it is even more important that you switch out the mix.

I live in NY so these trees will be coming inside before the first frost. I looked into the 5-1-1 and gritty mix and had trouble finding the materials, and am new to citrus, so I opted for a simple sand/compost mix. The trees seemed to be doing fine in this mix, but I think changing it out would be a good idea. Where could I find the ingredients for either of these mixes online? And what exactly do I need.

Since you will need to bring the trees indoors, I suggest using the 5-1-1 because it is much lighter. You will need 5 parts Reptibark (from a pet store in the reptile department). I buy it from Amazon because it is often cheaper on sale. You can also use pine bark fines (but I prefer reptibark). Then, 1 part peat moss, 1 part perlite, and about 1 tbsp of garden lime. I also add a scoop of Oscomote plus. Stir it all up and shake out as much of the old mix as you can. Most of us soak the reptibark before using it, but if you can't manage that, I've managed fine without is. Just water very thoroughly afterwards.

Brown tipped leaves sometimes indicates excess fertilizer. Loosen the ties to the stake if you haven't already.

Thanks you guys for all the great info! Really appreciate it. Found all the ingredients for the 5-1-1 mix on Amazon so I will try that. Hopefully this will solve my problem.

Great! That is a move you will not regret. Make sure you fertilize regularly with Foliage Pro also.

Oh yeah, and like Tim said, lose the stake. It will weaken the trunk.