Expert: Long Island Gardener - 3/24/2007

Question
when should i fertilize my old daffadils

Answer
Assuming your Daffodils are growing in terrific soil, a little Superphosphate applied right until the foliage is gone will boost your Daffodil blooms for next year.

NEVER apply Nitrogen to Daffodils.  That can be a problem if your Daffs are growing in the lawn.  Nitrogen is connected to bulb rot and you need that like a hole in the head.  That means Miracle-Gro is out of the question.

Lots of Daffodilphiles are old school gardeners -- they have been using malathion and Sevin for years and are still breathing and relatively healthy, so they see nothing wrong with chemicals.  The basic Intelligent Gardener approach of our new, round-earth approach is to feed the soil, not the Daffodils.  A handful of bonemeal under those bulbs if you can lift them at all will generate Phosphorous for YEARS with no help from you.  It will be constantly available and there is ZERO chance of burning the roots even if you never dilute the stuff with dirt.

So I'm with Bone Meal.

Superphosphate is risky but you sound like you have been doing this a while and probably have a bag of that in the garage right now waiting to be used.

So go ahead and fertilize asap.  Just don't give them too much of a good thing.  Phosphorous may be all they need.  Phosphorous will max out their flower genes and roots.  It's the middle number in the N-P-K on the label.  Go for it.