I saw this incredibly thorny plant while walking in Lynch’s Woods Park, Newberry, SC. There were a few tiny leaves on the tall green vine (over 6 ft.) covered in very long thorns. In complete contrast there were several white bloom clusters. I have never seen this plant and would be interested in knowing its name.
your shrub is called trifoliate orange, Poncirus trifoliata, sometimes put in the genus Citrus. It is related to oranges, but not edible because of the bitterness. However, they are important as a rootstock to which better citrus varieties can be grafted because this citrus is the hardiest. An interesting introduced plant with nasty spines.
Dr. Steven Hill, Botanist, SCNPS