It is also my understanding that nitrate nitrogen, in the form of potassium nitrate or calcium nitrate, is better absorbed at lower temperatures, so this is important for those bulbs that grow during the winter. The formulation I use has both ammonium nitrite and potassium nitrate, but the main ingredient is potassium nitrate. Diana Telos Rare Bulbs ----- > A word about nitrogen. Many years ago Fred Meyer told me that amaryllids > like Hippeastrum and many others (but not so much hardier fare like Crinum > or Narcissus) resent N in the form it typically appears in fertilizers: as > ammonia or urea nitrogen. I made the switch to orchid fertilizers such as > Dyna-Grow years ago just to get N comprised of mostly nitrate nitrogen, > with > a small percentage of ammonia nitrogen. I bloomed some difficult bulbs > when > I did this, plants that had not flowered for 10+ years previously > (Hippeastrum parodii, Paramongaia, etc.). Nitrate nitrogen is worth the > moderate extra cost in my view and it is not difficult to find brands that > use it.