Daylily Spring Sickness
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Frequently Asked Questions

What causes spring sickness?
It's been a mystery for decades - at least since the 1950's and possibly even prior to that. We think we are getting closer to an answer but more testing and observations are required. See the What's New page for information regarding possible culprits. Our experiments and observations do, however, rule out spring freezes after growth has commenced as a causative factor.

I have spring sickness in my garden, what should I do about it?
Because we don't fully understand the cause, and no experimental treatments so far have succeeded in preventing spring sickness, most people just wait it out. Many fans will recover in time (this leads some gardeners to think that a treatment has succeeded whereas in fact the plant would have recovered anyway). Alternatively, some suggest cutting off the affected fans at soil level in order to make the plant look more presentable.

Does spring sickness only occur in the coldest USDA Hardiness Zones?
No, for instance the spring sickness task force members cover zones 3 to 9 in various areas of the United States and Canada.

Is the whole daylily clump affected?
Not necessarily, usually it is only a few fans but it can happen that most or all of a clump is damaged.

What are the first signs?
The clump appears normal for a while in spring, but then some fans start to curve sideways and slow down or stop growing. The healthy parts of the plant keep on growing, so the affected ones become more obvious as they get left behind.

Are the leaf edges brown and ragged because a pest has chewed on them?
It doesn't seem to be recent pest damage. Those ragged edges start off very small as rows of "cuts" when the fan is still below ground. As the fan grows, the damage grows along with it rather like when you carve your initials into a squash when it is small, and they enlarge as it grows bigger. We're currently working to find out what causes the "cuts", which may well be a pest but the damage occurs long before you actually see it.

What happens to the stunted fans which don't seem able to outgrow spring sickness?
From what we have observed it appears that some will eventually start growing again quite late in the season and some will disappear completely. In a larger clump, the surrounding healthy leaves may eventually conceal the stunted fans from casual viewing giving the erroneous impression that all is well.

Is spring sickness caused by fluctuating weather conditions in spring?
It doesn't appear to be related since plants experimentally brought indoors in late autumn have still developed spring sickness without further exposure to the weather.

Does fertilizing too early in spring contribute to spring sickness?
It seems unlikely since several spring sickness task force members do not fertilize in early spring and yet their gardens are badly affected by spring sickness. In fact daylilies left unfertilized for a year or two as an experiment showed no decrease in the incidence of spring sickness.

Some tender daylilies get mushy or distorted leaves after a frost, is this spring sickness?
No, it isn't. Unless the fans stop growing or slow right down, curve, twist or grow sideways, and develop the typical brown ragged edges and holes in the leaves, it wouldn't be classified as spring sickness. If you are unsure as to whether you are seeing spring sickness, visit our image gallery and our diagnostic images page.

Will the same plant get spring sickness every year?
Not necessarily. A clump can be affected one year and not the next. Even separate clumps of the same cultivar don't always get spring sickness in the same year in the same garden.

I've heard spring sickness only occurs in the north, is this true?
Certainly most complaints about it come from the north! Reports have come in about plants being affected in the south but it may be that they don't get it as badly, thus people are not as concerned. On the other hand, not all northern gardens see spring sickness.

Does spring sickness only occur in North America?
We have had a few reports of spring sickness from other continents.

Is it only evergreens that get spring sickness?
No. The task force hasn't determined any tendency for evergreens to be affected more than any other daylily. They may get damaged by late frosts and look mushy and distorted, but that isn't spring sickness.

I've heard that the plants which get spring sickness are mostly modern hybrids.
We have observed spring sickness in many older cultivars and even species daylilies.

I've been told spring sickness is caused by thrips.
Some growers are convinced that thrips are involved. These reports usually come from the south and we're not sure if it is the same as the damage described on these pages. While we are keeping an open mind on all possibilities, we have not seen any evidence to connect thrips to spring sickness. See the What's New page for the latest information regarding possible culprits.

My friend says insecticides cure spring sickness.
We think it unlikely that spring sickness can be cured once symptoms have appeared because the damage seems to be done some time before it becomes visible. Some people have suggested they've lessened the severity of spring sickness with insecticide treatments in spring but we have so far been unable to duplicate that result, although cannot rule out the possibility. There have been reports of insecticides being used in the fall to prevent spring sickness the following year. Again, the task force has tried to duplicate these treatments without success so far. It's possible we haven't got the timing or product right yet.

If you haven't been able to prevent spring sickness with insecticides, does that mean it isn't caused by a pest?
Not necessarily. It's difficult to know when to treat and with what when dealing with an unknown enemy! Some pests are not susceptible to certain pesticides and some are just plain difficult to control. One suspect, the bulb mite, is notoriously difficult to control with pesticides on plants in the ground.
Could it be a fungus? I've heard it said that a fungicide can prevent the damage.
A fungus is suspected to be involved in some way, but to what extent we do not know. The daylily leaf streak fungus, Aureobasidium microstictum, has been consistently found in spring sickness lesions on laboratory investigation. But this fungus is thought to infect the plant through a wound of some kind - perhaps this is where a pest is involved. We have heard of several unsuccessful attempts to prevent spring sickness with fungicides. Perhaps now that some gardeners are spraying their daylilies with fungicides on a regular, ongoing basis to combat daylily rust we will find out if these products also have an effect on spring sickness. However, the few reports that have come in so far indicate that spraying fungicides for rust has not prevented spring sickness.

It's often said that spring sickness is no big deal, the plants grow out of it and bloom anyway.
Fans affected by spring sickness can remain stunted and not bloom, although many do restart growing and produce scapes. Often the quality and number of blooms is disappointing though. It is a particular problem for daylily sellers, since spring sickness occurs around shipping time and most do not like to send disfigured plants. Hybridizers are also greatly inconvenienced by spring sickness, since badly affected seedlings and newly acquired divisions may take longer to bloom.
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