coco perlite. Usually do not have issues with it long like that. Just right IMO if to do the paper towel method.You should really get that thing planted before the tap root is that long.
What medium did you plant that in?
What are you feeding it?
My about me has most of my setup listed. Low EC coco, rinsed it til the bucket read .16 EC then poured distilled real quick until runoff came out and read .27 EC or .2EC. mfg flora trio food system. .45EC 1.8ml/gal of each nute.What are you feeding it?