i log in everyday. I did pick some spines off it but there wasn't a clear option prior from what i remember either. My friend im talking to atm however had the 'clear' option even after collecting spines.
I have just loaded a copy of your save and after waiting a short amount of time the cactus fully grew and I was able to harvest it and then chop it down.
Not sure how you have got into this situation but letting the tree regrow should fix the issue.