Q: When is the time to fertilize spring bulbs like daffodils and hyacinths?
A: One of the adages of garden fertilizing is to feed plants when the leaves are growing.
When the leaves of spring bulbs poke out of the ground, they mark the beginning of the bulb fertilizing season. This is the time when roots are most active. Daffodils aren’t heavy feeders, so they don’t require a lot of fertilizer.
There are two times to fertilize spring bulbs: in September, with slow-release fertilizer (Osmocote, Dynamite, Milorganite, etc) and in late February with fast-release fertilizer (10-10-10, Miracle-Gro, etc).
This is the rationale: by feeding slowly from September through February, bulb roots absorb nutrients and the bulb prepares itself for flower emergence in spring. Then, a fast-release fertilizer applied in late February, well before flower emergence, stimulates leaf growth, which feeds the bulb after flowering.