The best time to apply the fertilizer is when they start to emerge from their winter sleep. Several types of fertilizer can be applied. Bone meal is a good source and is organic. The use of bone meal alone may leave the plants starved for nitrogen. A combination of bone meal and blood meal is better suited for overall health.
Bone meal provides an excellent source of phosphorus but little nitrogen.
The blood meal will add the nitrogen to help build a strong bloom for next year. For a clump of five to seven bulbs, a handful of each organic fertilizer is recommended. Commercial fertilizers are also good for bulbs. A small handful for a grouping is all that is needed. If possible, lightly work all types of fertilizers into the soil.