Beautification Committee member, Diane Smith recommended this article from Horticulture web site. Certain perennials do not benefit from additional fertilizer. Before you spring-feed your garden, review this list of perennials not to feed.
Most perennials don’t need a lot of feeding, particularly if the soil is healthy and rich and was prepared well at planting time. A spring top-dressing of compost may do the trick. In areas with poor soil, a once-annual application of granular fertilizer in spring will suffice for most perennials. Exceptions include “heavy feeders” such as mums, lupines, lilies, delphiniums, astilbe and border phlox.
Perennials that do best with no supplement fertilizer include butterfly weed (Asclepias tuberosa), false indigo (Baptisia australis), asters, pinks (Dianthus spp.), rock roses (Helianthemum spp.), sea holly (Eryngium spp.), bee balm (Monarda didyma), speedwell (Veronica spp.), coneflowers (Echinacea spp. and Rudbeckia spp.) and all ornamental grasses.