Maggie's Farm

If you want to fertilize gardens, shrubs, lawns, trees, etc, we recommend doing it in March or early April before there is any significant budding or growth. In any event, as soon as the soil thaws. Why is that?  It is because roots wake up and get hungry before anything appears visibly on plants. Some years I have fertilized right on top of a late snow.

Also, because it can take time (and plenty of rain) for surface fertilizer to dissolve and to get deep into the soil. 

Well-established perennial and shrub borders in half-decent soil only need a sprinkling of all-purpose fertilizer. I imagine that it makes for better blooms. In nature, the fertilization would come from rotting leaf litter, etc. and, besides, the plants would be growing where they want to grow instead of where you want them to grow.

Do plants grow at night? Not much because they prefer to be solar-powered. However, roots do reach out in the dark (obviously) on stored energy as soon as the soil thaws to provide the nutrients to produce later foliage and bloom. Think of Sugar Maples, or spring bulbs. Sugar Maples (and all trees) have enough deep roots below the freezing level to begin sending nutrients up the tree while the surface soil is still frozen.

For later Spring, seasonal vegetable gardens do need fertilizer of any and all sorts. They love it. Vegetables are so far from natural that they would never survive without special care. Same goes for ornamental plants. Never fertilize herbs, though, because their fragrances benefit from poor nutrition.