Others showed no effect. We cannot make firm recommendations on the use of this product without research results on other tree species. The best time to apply fertilizer to spring-flowering bulbs is when the foliage emerges in the spring, not at flowering. Traditionally, gardeners have applied fertilizer during bloom or a bit after. But because the roots of these bulbs start to die at flowering, fertilizer applied at that time is wasted.
Roots are active when the foliage first pokes through the ground.
Nutrients applied then are used to produce flowers the following year. If bulbs have been fertilized in the past, there is often plenty of phosphorus and potassium in the soil. It is best to take a soil test to be sure. This would equal 1 rounded teaspoon per square foot. If phosphorus and potassium are not needed, blood meal makes an excellent fertilizer.