Solving Daylily Problems

Tips on how to use this section
The symptoms of the most common problems are in the left column of the chart. In the right column are the probably causes of those symptoms. For those problems for which there is detailed information in a different part of Yardener’s Helper, the name of the problem is linked to a detailed file. For those problems for which there are no additional files, the discussion is found in the paragraphs below the chart.

Solving Daylily Problems
SymptomsProbable Cause
Buds & Leaves Chewed or DisappearCritters
Leaves Yellowed; DistortedAphids
Leaves Die In SummerNormal Leaf Senescence
Leaves SpottedSpring Sickness
Wet Blotches under LeavesEdema Blisters
Leaves and Buds DeformedMites
Buds Shrivel; Drop OffThrips
Large; Ragged Holes In LeavesSlugs or Snails
Leaves Develop Yellow StripingLeaf Streak Fungus

Buds & Leaves Chewed Or Disappear Because of Critters
Daylilies are favored by several kinds of wildlife that may frequent your yard. Deer are particularly fond of the tender emerging daylily shoots and flower buds. They will nibble them to soil level in just one evening. Discourage the occasional deer visit by spraying plants with one or more of the animal repellents available. Follow the label directions. If your local deer are under severe pressure for food, they will be eating mature daylily plants and other plants on your property as well. Only a fence will effectively deter starving deer. Chipmunks, voles, or mice may nibble on daylily shoots or fleshy crowns at soil level. Deter them by covering the clumps of emerging daylilies with wire mesh covers until foliage is grown enough to be less appetizing or use hot pepper wax.

Leaves Die In Summer Because Of Normal Leaf Senescence
Although some types of daylilies are evergreen throughout the winter, many normally die back in the fall. After flowering, they begin to look a bit ratty with browned leaf tips and dead leaves in late summer. Remaining stems dry out. This is normal. Pull out the brown leaves and dried stems. With a dose of fertilizer reblooming types continue to produce flowers, although not in the abundance of early summer. Eventually, with frost, all the foliage will die back and need to be cleaned up.

Leaves Spotted Due To Spring Sickness
Occasionally the leaves of daylily plants develop yellow spots or brown blotches or streaks on them or new growth that looks rough. Some plants die from the top down. They don't bloom as heavily as they should. These are the symptoms of a problem called spring sickness, which is actually cold injury caused by late spring frosts. The leaves and flower buds are damaged before they emerge from the crown of the plant, and symptoms may not show up until weeks later. A heavy winter mulch of chopped leaves, wood chips or pine needles sometimes helps prevent this problem. Try covering the plants with white polyspun garden fleece before they emerge. Trim off browning leaves at the base. Some purple and lavender daylily varieties seem to be especially susceptible, so try other colors as well as varieties reported to be especially suited to colder climates.

Wet Blotches Under Leaves Are Edema Blisters
Edema is caused when plants that have endured dry soil too long suddenly receive lots of water. Because they tend to take up the water more quickly than they can transpire moisture from their leaves, overfull cell tissues swell. They form blisters that eventually dry and turn brown. Unlike their tough roadside tawny cousins that can handle drought, hybrid daylilies need an evenly moist soil at flowering time. Trim off marred foliage, and wait for soil to dry a bit for plants to recover.

Leaves Develop Yellow Striping From Leaf Streak Fungus
A fungus that thrives on moist daylily leaf surfaces and causes length-wise yellow streaks accompanied by irregular darkened spots that disfigure the leaves. Flowering may also be reduced. This is primarily a problem in the spring, since the fungus does not survive temperatures over 90°F. Because some types of daylilies are more susceptible than others, the fungus may attack only certain ones in your yard.

Pick off and discard infected leaves. Remove dead plant debris promptly from the garden, to reduce overwintering spore populations. Dig up and discard seriously infected plants with surrounding soil to control the spread of the infection. Mulching helps prevent splash-borne infection in plantings. To protect uninfected plants in the area spray their healthy foliage with garden sulfur according to product label instructions.
For more information see the file on Dealing With Fungal Diseases.