The Gloriosa or Flame lily grows from tuber like roots that love a moist soil with good drainage but this plant is not picky about fertilizer. Just use an all purpose plant food such as Osmocote at planting time. It is more important to mulch the soil on top of the lily to seal in some moisture and to keep the soil moist than it is to use a specialized plant food or fertilizer.  Like with most bulbs, a slow release plant food is better than a water based plant food delivered when the plant is getting ready to bloom. Too much fertilize will cause the exotic looking flowers to open quickly then fade quickly. Slow and steady is best for fertilizing this plant and better to feed too little rather than too much. Keep growing, Marianne Binetti