As the last snows mostly melt, the soil defrosts a bit, and the blackbirds return, it's time to fertilize flowering shrubs and trees and perennial beds in Yankeeland. Any further snows will be short-lived.
Remember that roots of grasses, perennials, shrubs, and trees begin growing long before green shoots appear. By the time growth appears, it's sort-of too late for plants' spring feeding - especially woody plants. It takes a while for the food to get into the soil, and even longer to get down to the roots and then up into the plant.
Rain is required. I cheat and put Preen on the perennial beds. It's not perfect, but it helps. For shrubs and roses, I use a stick to poke a 6-10" hole near the drip line, and pour some all-purpose fertilizer in there. Just like Jesus' fig tree parable.
If you got too busy to do it in the fall, now is the time. I did my shrubs, roses, gardens, boxwoods, and lawns yesterday, and used up an old bag of Hollytone and an old left-over bag of lawn dolomite (lime) too. I have hollies and hybrid Rhodies in sheltered spots and a few Azaleas too where they are well-protected from winter winds even though we are north of the hybrid Rhodie and Azalea happy zone. North of the Holly zone too, but I love my hollies and the birds do, too.
Heck, I can even get good hardy Crepe Myrtles to thrive here if they are well-sheltered and against the house. Green thumb, or dumb luck? They are well-sheltered, and close to walls and foundations. When they are in bloom up here in August, people wonder what the heck they are because they are a southern shrub/tree.
Need to remember to get my lawns plugged in early June, but I will probably forget to do it because it makes for a week of muddy dog paws on the beds and couches. A hard-packed lawn is an unhappy lawn, and our local tool-rental place rents lawn-pluggers. Fortunately, I decrease our lawn size every time we add a new garden. That's good - but weeding and mulching new gardens is bad. Too hard. In a while I will mulch the heck out of the gardens and let summer do what it will.
Can't win. But fertilizing is worth it.