No, nobody knows for sure. There may be pious commentary as to what it was or some mystic who reports some vision. Neither is required belief of Catholics.
If one is truly interested, there have been studies which indicate what plants were generally in the area and which normally have thorns, and one could draw one’s own reference from that. While I don’t have a specific reference to such, I have seen comments in regard to the Shroud which indicated what grew there then.