Don`t forget that some tree species have only a draft of the genome... like cotton and rubber tree for exemple... This is because of the complexity of the genomes, once sometimes there is a lot of repetitive sequences. The NCBI has 66 entries that corresponds to whole genome sequences of "trees" deposited in the databank.
Apparently, there is only one tree for which the complete genome has been sequenced: Populus trichocarpa (Black Cottonwood).
There are several more if you would count completed genetic maps, e.g. Hevea brasiliensis (latex rubber tree), Corylus avellana (hazelnut), and several Prunus species.