Thank-you for this post.
I was fortunate enough to see a relic of the True Cross and one of the thorns of Christ’s Crown during a pilgrimage to Rome. The thorn was wicked-looking, over an inch long, not a rosebush thorn.
Yes, the thorns used for our Lord’s crown were of a spurge family called “Euphorbia milii.” Click here to see a good photo of the bush and thorns. It’s a pity the crown is so often depicted as having smaller, less fearsome thorns. Imagine the Roman soldiers then using reeds to force that crown farther down onto our Lord’s precious Head.