To cut back spent growth on daffodils, remove the flower stem by cutting it at the base, or snap off the faded flowers, being sure to take the base of the flower. Now allow the foliage to grow and mature and ripen. When it turns at least half way brown, trim it off at the ground and dispose of it in the trash. The bulbs should emerge again next spring. You might give them some complete granular fertilizer, in the fall when they begin to root and again in early spring when they begin to come through the soil.