Why Are My Daylilies Dying?

When daylilies weaken and die over the course of a season, it may be due to lack of water, sunlight or friable soil. Sudden death, however, requires rapid diagnosis and treatment to save other daylilies in the garden.

Disease

Two diseases threaten daylily lives: crown rot and daylily rust. Crown rot starts in the crown and turns leaves yellow until the crown dissolves and the plant collapses. Daylily rust, diagnosed in the U.S. only since 2000, grows on leaves in reddish-brown patches, eventually destroying them. Both diseases cause death if not caught quickly.

Herbicide

Pre-emergent granular herbicide products are recommended by experts like those at the University of Tennessee Plant Sciences because grassy daylilies are sensitive to spray herbicides like glyphosate and glufosinate, whose drift can fatally weaken or kill a plant within 7 to 14 days.

Lifestyle

Daylilies require cooling periods to bloom; dormant varieties must spend several months in dormancy. Evergreen varieties can adapt to the longer cold period of northern zones but dormant plants in southern zones may die for lack of sufficient cold weather to trigger hibernation. Best practice is to purchase plants that have spent their first years within two growing zones of their new home garden.

Growing Conditions For Daylilies

The fragrant, fast-growing daylily fares best in full sun or partial shade of four to six hours of sunshine per day. In Western states, the plants grow from spring through mid-fall. Many blooms open at dawn and close at dusk. For potted plants, make the hole just a little larger than the pot. Avoid planting in areas where water collects and sits. Add compost or other organic matter to the soil before planting daylilies. You can fertilize daylilies with all-purpose plant food early in the growth cycle. As the daylily grows, do not overwater in order to avoid root rot problems. Blooms vary and develop into triangular, star and circle forms at the top of leafless stems. Rust also attacks daylilies. To help avoid problems, keep areas around the flowers free of debris that may be hosts for mold and insects.