By: Sandy Feather ©2007
Penn State Extension
Q. What is the best time to fertilize established daffodils? I have read conflicting advice; some suggest fertilizing in the spring, while others say fall. What is the best fertilizer to use?
A. Daffodils and other bulbs put on significant root growth in the fall, so it is a good to time fertilize them. Root development continues until soil temperatures fall below 40 degrees and then resumes in the spring as soil temperatures warm. However, in the spring, more energy is expended producing foliage and flowers than root development. If you forget, or run out of time to fertilize bulbs in the fall, spring is the second best time.
For established bulbs, rake back the mulch and broadcast a granular fertilizer across the soil surface. Replace the mulch to protect the soil surface from erosion and nutrient loss to runoff. The fertilizer will be carried down into the soil with rain, snow melt and winter's freeze-thaw cycles.
If you fertilize in the fall, a slow-release source of nutrients is best, such as an organic fertilizer or an organic-based fertilizer. Whatever slow-release fertilizer you choose, be sure it is low in nitrogen and higher in phosphorous and potash. All fertilizers are labeled with three numbers that indicate the percentage of those nutrients. They are always listed in the same order: nitrogen-phosphorous-potash.
Brent and Becky Heath from Brent and Becky's Bulbs recommend a fertilizer called Bulb Mate, with an analysis of 5-10-12. However, if you fertilize in the spring, a more water-soluble source of nutrients is a better choice, such as 5-10-10.
Organic and slow-release fertilizers have to be broken down into a form that the plants can use, usually by microbial activity. When you fertilize in the spring, slow-release fertilizers may not be broken down in time for the bulbs to use the nutrients before their summer dormancy.