How long will a parasite live on a live aquarium plant?

So a few moths ago my aquarium got some sort of a parasite (they were worms just can't remember exactly what it was called) and we bleached/boiled our entire take and everything in it and threw most of our live plants away. We did keep one plant but did not return it to the tank, it's been sitting in a vase with water for about 3 months. My question is do you think it would be safe to put it back in the tank? Or could that parasite possibly still on the plant? thanks in advance =)