Peters Fertilizer is a commercial plant food and there are different formulas of this brand as professional growers often use it for different crops. It is a fertilizer that is mixed with water (warm water works best) and then applied to the leaves or around the soil of the plants. The dosage depends on what you are feeding and how often you plan to fertilize. I suggest visiting the company's website to find the correct dilution. In general, I would not fertilze plants at the time they are transplanted. Lily of the valley plants have underground stems that are similar to bulbs. They will not need fertilising when transplanted, and this fragrant bulb is such an enthusiastic grower, I would not fertilise it at all - in fact, many gardeners regret planting lily of the valley bulbs as they spread very fast and can crowd out other plants.  May your lily of the valley grow only where you want it and enjoy the fragrant blooms. Keep growing, Marianne Binetti