Concise Bible Dictionary:
The crown placed in derision on the head of the Lord Jesus, when arrayed in a scarlet robe. Though applied to His sacred head by the rough soldiers, it was connived at by Pilate, who presented the Lord in this garb to the Jews, but which only drew forth their cry, “Crucify Him.” We read that the robe was taken off Him, but nothing is said of the crown, so that He may have worn that on the cross. It is supposed to have been made of the Arabian nabk, which has flexible branches with very sharp thorns, and ivy-like leaves: mocking the Lord, as some think, both as a king and as a victor (Matt. 27:29; Mark 15:17; John 19:2,5).
Nabk – Ziziphus spina-christi