there's a few things that can help/ prevent it from growing.
1) Make sure the top of the bulb is indeed placed upwards
2) Often helps to let it stick out of the gravel/ sand a lil bit at its tip rather then fully bury it
3) Inadequate light for plants over the tank? (Since its so far down, if there ain't enough light reaching it can't grow)
4) Water maintenance / usage of ferts.
Now this is only guess work, obviously I donno your tank or whats exactly going on there, so I can only follow process of elimination to help. But I have raised several just fine (see picture early in this thread) so if I can help ya, i'll be glad to do so