This technique has never been seen in its normal state but from what can be said from its Fire Monk version (without the flames added), Gabimaru grabs a tree and thrusts it towards his opponent, using the branches as a means to injure his target.
Fire Monk Version
Gabimaru can use a Ninpō: Fire Monk version known as Ninpō: Thorn Quilt — Fire Monk Version (忍法 棘衾 火法師拵え Ninpō: Toge Busuma — Hi Bōshi Bājon?). After combining Fire Monk with Thorn Quilt, Gabimaru sets the tree on fire and thrusts it towards his opponent. This is called Ninpo: Quilt of Thorns, Ascetic Blaze Mode in the Viz Manga.