I have a BF inside and I've had it for several years. I live in the high desert of S. California where the humidity is very low (sometimes in single digits). I only turn on my air conditioning if its 90 degrees F outside. My fern never gets any sun--not even dappled. Its next to a window, but out of the sun, and it has a little tabletop water fountain right next to it to help with humidity. I also mist it most mornings. I don't ever let it dry out completely, but don't keep it soaking wet either. I water it every few days, or when the pot starts feeling lighter in weight. I wonder if yours could be rotting, due to too much watering? The black leaves have me wondering about that. Anyway, if I can grow one, you surely can too! This is mine. I know its not real full, but its healthy!
