Don't be perplexed, Gabrielita :-) What you're seeing is your rootstock taking over. Orange and mandarin trees, whichever it is you have, are almost always grafted. They have one variety of rootstock, and then the actual tree you've bought has been grafted to that rootstock. That gives you a tree very very hardy, disease-resistant roots that grows the fruit you want. So, you're going to need to prune away all the shoots coming out from the rootstock so the upper graft part has a chance to recover. It should, but first you've got to remove those rootstock shoots. You'll be able to easily identify the rootstock shoots because they will look different (the leaves will probably be in three's), and those shoots will be growing from beneath the graft line (look closely at the trunk down low, and you should see a distinct line where the scion was grafted to the rootstock.) After pruning, fertilize the tree with a good citrus fertilizer, water in, and see if the top part of your tree recovers. This winter, be sure to protect your tree with a cover if you have freezing temps, again. Make sure the cover does not touch the leaves (put some stakes all around the tree), and the cover should come all the way to the ground. You can also run a set of mini Christmas tree lights through the tree, then put your cover on, to keep the tree warm.

Patty S.

http://edis.ifas.ufl.edu/hs221

if the leaves look like the ones in the link, cut the branch off.

the rootstock is taking over atm, that's why the top (grafted part) is weakening, and has small, shriveled leaves.

here's a nice picture tutorial about suckers
http://www.fourwindsgrowers.com/solver/suckering.html