Daylily Blossom Problems

Daylilies, in the genus Hemeorocallis, are a flowering ornamental plant that is free of major diseases and pest in the United States. However, the blossoms are susceptible to an over watering condition known as oedema.

Causes

Oedema is a condition of daylilies caused when the plants roots take in more water than the plant can transpire, reports the University of Cornell Plant Disease Diagnostic Clinic. Over watering, low sunlight and high humidity are favorable conditions for the disease. Although daylilies are susceptible to oedema, other plants that exhibit the symptoms below may also suffer from the conditions. However, because daylilies are relatively pest free, oedema can explain diseased looking blossoms on daylilies.

Identification

Daylily plant cells affected by oedema enlarge due to the excess water, eventually causing them to explode. This process causes yellow to black diseased blisters on the edges of the blossoms, reports the University of Minnesota Extension. The blisters remain on the blossoms until they fall, but do not persist perennially if controlled. However, the damage is aesthetic and rarely causes lasting damage.

Control

Control for oedema consists of avoiding over watering, increase lighting conditions, water in the morning and increase air circulation, reports the University of Minnesota Extension. Reduce watering to the plant during periods of high humidity in order to prevent oedema. Check soil moisture before watering. Dry warm weather conditions will require more irrigation, while cool rainy conditions will not require irrigation.

How do I know if the symptoms are from oedema or another disease?

The difference between oedema and other plant diseases is that symptoms do not persist year after year, as long as the soil moisture levels are ideal for your plant. A good way to check soil moisture levels is to stick a toothpick into the soil. If there is soil residue sticking to the toothpick, then the soil has adequate moisture. However, if the toothpick comes back dry, or has barely any residue, then it is a sign that it requires moisture.

The leaf yellowing and blacking caused by oedema is common of root rot and some leaf spot fungal infections, as well as leaf burn from an excess of nitrogen in fertilizer. However, oedema occurs when too much water builds up in soil and plants take in this water. Dig up the daylilies or other plant you suspect suffers from oedema and check the soil and root system. If the soil has excess moisture and the root system appears disease free, then oedema is the most likely the problem. However, visible fungal growth or other noticeable plant problems are an indicator of disease.

Sources:

http://pubs.ext.vt.edu/426/426-030/426-030.html

http://plantclinic.cornell.edu/FactSheets/oedema/oedema.htmhttp://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h113oedema.html