Information about fertilizing daylilies can be confusing. The easy-care perennials have become increasingly popular. Where once the gardener's choice was between dozens of varieties, today's hemerocallis fancier has a choice of hundreds, some of them priced beyond most garden budgets. Although most are undemanding, many have specific needs. All can benefit from a planned program using the right fertilizers.
The charms of varieties like lemon lily, kwanso and the eternal tawny or ditch lily are largely based on their toughness. Plant them in a well-drained, slightly-acid soil and give them morning sun, and they'll bloom and grow nearly forever. However, even these oldest varieties benefit from some nitrogen to keep their foliage green. When planting older varieties, a handful of well-rotted compost or manure in the planting hole will provide well-conditioned, fertile soil for a good start. All these older varieties need a feeding of slow-release nitrogen fertilizer each spring. Some gardeners make their own fertilizer add fish emulsion, manure and micronutrients to garden fertilizer. The Southwest Indiana Daylily Society suggests that a garden fertilizer with an N-P-K balance of 6-12-12 or 10-10-10 in the soil around the daylily each spring and plenty of sunshine and water may be all that daylilies ever need. The Society notes that some gardeners choose to fertilize again in late summer or early fall.
The dozens of varieties produced by hobbyists and scientists from A.B. Stout's experiments in the 1930s through the 1950s Siloam hybrids are more demanding than the older daylilies. They require more sun and stable soil fertility than their forebears. The University of Alabama Extension recommends the following; for fertile soil, one application of a 12-3-6 or similar fertilizer in the spring; and for sandy or low-fertility soil, an application of balanced (13-13-13 or 10-10-10) garden fertilizer at the beginning and again at the end of spring. The Extension also suggests an application of aluminum nitrate for extra nitrogen in June. Popular liquid garden fertilizers have N-P-K ratios similar to the balance recommended for fertile soil. Mulching with compost provides traces of slow-release nitrogen to plants. Safe Haven Gardens nursery near St. Louis suggests using garden gypsum to supply calcium and sulfur and Epsom salts to provide and magnesium and sulfur to soil that needs micronutrients.
Newer hybrids have remarkable color and unusual flower forms. Semi-evergreen forms keep their foliage almost all year long. They also grow farther south than the older daylily varieties. Safe Haven Gardens recommends soil testing before planting any daylilies. It is imperative with these newer varieties. The breeders of these exotics provide the best sources of information about fertilizing them. Southern daylilies may require three feedings in long-season areas, according to Florida's IFAS University Extension. Safe Haven suggests that gardeners should use a 20-5-5 or 20-5-10 to cut down on phosphorus, which, unlike nitrogen, stays in the soil. The nursery also recommends avoiding fertilization while scapes, the tall stem that bears flower buds, form. This is particularly important for exotic forms because nutrients affect the way inflorescence, or flowers, form. Time-release fertilizers offer pelleted forms, some of which also include micronutrients like calcium, sulfur and magnesium.