Diseases in Daylilies


  • Daylilies do not grow from a bulb. Instead, daylilies possess a crown where the roots and foliage emerge from. The plant’s crown gives it life. Consequently, damage to the crown causes death to the entire plant. In addition to the crown, daylilies consist of long, strap-like leaves that are smooth or slightly ribbed. They grow in an arch-like formation, called a fan. A daylily’s foliage varies in color from light green to a darker green that looks almost blue in color. The plant also includes flowers that bloom in bright colors. Know how to protect your daylilies from common threats to ensure their prosperity.

Crown Rot

  • Also known as bacterial soft rot, crown rot is an infection caused by bacterial infestation rather than a virus or fungus. Bacteria enters the soil and infects daylilies through an existing opening. Once infected, daylilies emit an unpleasant odor. They begin to rot, becoming soft and squishy. When infected daylilies exist in areas containing high moisture levels, the bacteria grows quickly and kills the plant in a matter of days. To prevent daylilies from crown rot, soak them in a mixture consisting of one part chlorine bleach to three parts water for 20 minutes. This solution will eliminate bacteria from plants before they enter and contaminate the entire garden. It will also treat plants already suffering from crown rot. Simply remove the daylilies from the flowerbed and cut off any infected parts. Treat the rest of the plant with the chlorine bleach and water mixture and sterilize the flowerbed before re-planting it. Do not re-plant the previously infected daylilies in the original spot. Always rinse the solution off the plants before planting them in your garden.

Daylily Rust

  • A type of fungal infection, daylily rust attacks the plant’s leaves and scrapes. Daylily rust appears as a colored growth known as summer spores or winter spores. Summer spores germinate during mild winters, resembling a yellow-orange color. Once established, summer spores can infect daylilies during the entire year. Winter spores appear black in color, germinating during the end of each growing season when days are short and temperatures are cool. Winter spores manifest on dead leaves and lay dormant until spring. They are much more resilient than summer spores. To prevent contaminating a garden of daylilies with daylily rust, isolate new plants for an entire growing season before integrating them into your nursery.

Spring Sickness

  • When infected with spring sickness, a daylily’s fans grow in a mass, causing the entire plant to lean sideways. Leaves develop jagged, brown edges and perforations, coming apart from the plant base because of decay. While some fans overcome the affliction on their own, blooming eventually, other daylily fans experience limited growth and even death. Although no one knows what causes spring sickness, gardeners notice that the disease develops before new growth emerges from soil in the spring.

Root-Knot Nematodes

  • Clemson University’s Cooperative Extension identifies root-knot nematodes as a disease threatening the life of daylily nurseries. When established in the daylily’s root system, nematodes contribute to the plant’s decline. Root-knot nematodes infect daylilies so that they cannot grow healthily. Daylilies lose their green color, turning yellow and wilted. Roots develop tiny bumps that provide food for nematodes. In return, root-knot nematodes release toxins into the plant, infecting it. Nematodes typically infect daylilies grown in damp, sandy soils and are more prevalent in residential land that was once used for crops.

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