Most garden perennials don't need fertilizing if the soil is healthy and matches their preferred growing situation. A spring topdressing of compost will usually be all that the gardener needs to support perennials' growth, particularly in newly planted gardens or where the soil is poor. For some plants even this may be too much. Perennials in overly rich conditions will let you know by putting on excessive growth that tends to flop and require support.
Related: Learn about your soil so that you can choose perennials that will naturally grow well in it; see "Gardening Basics 2: Your Garden's Soil Type."
Perennials that do grow better with regular applications of fertilizer are known as heavy feeders. These include mums, lupines, lilies, delphiniums, astilbe and border phlox (Phlox paniculata).
Related: "Tips for Growing Delphiniums"
Perennials that perform better with no supplemental fertilizer include butterfly weed (Asclepias tuberosa), false indigo (Baptisia australis), asters (Aster, Symphyotrichum and Eurybia), pinks (Dianthus), rock roses (Helianthemum), sea holly (Eryngium), bee balm (Monarda didyma), speedwell (Veronica), coneflowers (Echinacea and Rudbeckia), sedums (Sedum and Hylotelephium) and all ornamental grasses.
