My favorite technique is to use a liquid fertilizer at half strength in three applications - if I am organized (rare occurrence) that would be pre-bloom but well leafed out, post bloom, and three to four weeks after the flowers fade but before leaves yellow. I like Jack's Classic Blossom Booster, which has a 10-30-20 analysis. It is absorbed through the leaves as well as taken up by roots so I mix and just slosh over the plants using a watering can. Very good when lifting, dividing, and replanting bulbs still in leaf. Judy in New Jersey on a nice sunny day