Can anyone tell me what this shrub/sapling might be. I have had it on my balcony for 3 or 4 or so years, but this is the first yesr that I have noticed the long thorns on the maint stems. It is about 4 feet tall, and would be taller but I have trimmed it a few times. I don't know where it came from, maybe from a seed or fruit that I picked up somewhere, planted and forgot about.
