Why does my daylily stay a sickly yellow? It is on a drip system.

Can you include photos?

Too much water? If you have a newer plant, a deep soaking every 3 or 4 days is probably enough. If you have an older established plant, once a week is probably enough. Daylilies are xeric by nature, and in my opinion (I'll probably get jumped on for saying this), they are OK if they dry out every now an then. It may even be good for them, helping prevent rot, etc from constant moisture.

Photos would help, as suggested. Have you fertilized, and if so with what? Has there been a soil test? Have you checked that the drip irrigation is dispensing enough water to get down to root level for that plant? If you only have one daylily, are the other kinds of plants near it looking OK? There can be several causes of yellow foliage so, especially without a picture, it's a process of elimination. There are also fungal diseases that can cause yellowing.

I have a lot of yellow dying leaves this year, it seems to have come on suddenly after the first series of blooms. It could be the hot weather, but there was a short mention of daylilies losing many of their leaves because after blooming they no longer need so many leaves to support the blooms(the plant has bloomed out).
I do think that a lot of my leaves are just simply getting burned in the bright scalding sun, but there seems to me to be something to the theory of the plants "culling" the leaves after bloom. Anyone have any thoughts on that? But when I look and see that rebloom is getting under way and that those new scapes will have new blooms, well it seems those leaves would still be needed. The plants in the bog as well as the plants in the upper dryer beds are showing the sudden surge in yellow leaves...maybe signs of summer dormancy?

I think leaves dying back around or after blooming could just be a lifecycle thing. Do you see it more on "dormants" than evergreens by chance? It certainly happens here.

Older leaves turning yellow while a plant is growing could be a sign of nitrogen deficiency, when N is short plants move it from older leaves to newer leaves which are more important and that turns the older leaves yellow. But as Maurice has said, the lifespan of a leaf is not forever in any case. Even evergreen coniferous trees lose their older leaves (think pine straw), they just don't do it all at once every year like deciduous trees.

People often cut daylilies back after flowering to get a new flush of leaves for the aesthetics, we are growing them for their looks after all.

Maurice was saying that the plants would draw all the resources from the dying, yellowing leaves. But there would be a stage at which there would be little advantage to leaving those leaves on the plant. I was concerned about pulling those dying leaves off, but I don't think it would hurt the plants nearly as much as cutting back all the foliage on a plant, so I think I will continue pulling off all the lower yellowing leaves.

I do not consider that daylilies are "xeric" plants.
Some of the natural species tend to be associated with moors, bogs, etc. in their natural locations (for example, Hemerocallis dumortierii complex, H. dumortieri var. esculenta). Others may be associated with drier but coastal areas, for example H. fulva var littorea.

Every summer I put many potted daylilies into our pond. Sometimes, after heavy rains the pond level rises to above the pot rim. I have not lost a daylily yet. They seem to do quite well under those conditions and flower without any further attention on my part. I have been doing this for more than fifteen years to the same potted cultivars.

A couple of researchers have checked plant species for the effects of submersion under water for various lengths of time. One study compared ten species of plants with high adaptability to aquatic environments. Daylilies scored the highest for flooding tolerance as measured by plant height and leaf width. That strongly suggests that daylilies are adapted to moist/wet environments rather than xeric (dry) environments.

Thanks for that bit of insight, my bog daylilies are doing great. I had not associated that some of them do great yet a few of them can't take that amount of moisture and tend to have rot issues due to:
"Some of the natural species tend to be associated with moors, bogs, etc. in their natural locations (for example, Hemerocallis dumortierii complex, H. dumortieri var. esculenta). Others may be associated with drier but coastal areas, for example H. fulva var littorea ."
Only a very few have ever developed rot, so I continue to enjoy growing them in the bog. I don't have to water them even in drought, but everyday is a slog through the mud.

Have you ever felt like you were about to do something so stupid, that you know you shouldn't do it, yet you're going to do it anyway? That's how I feel now because I'm about to argue with Maurice on this xeric thing. don't do it... don't do it... ah, I'm doing it.

Arguing that a plant can't be water-wise or xeric because it can also survive while submerged is not logical, is it? That argument requires the assumption that a plant can't be both xeric for long periods of time, and capable of surviving while submerged during other long periods of time.

Most places where I've read about xeric gardening define it as gardening with plants that need limited watering. In one article I remember, because it's an easy to remember, suggest xeric plants only require water at most once a week. Where I live, it's been since spring of 2020 since we've averaged an inch of rain a week, as we've been in a severe or extreme drought for the last two growing seasons. I've not lost one established plant to the drought.

So, I was talking off the cuff, there, and I'm not really an expert on, well, anything. But I'm not without sources. Here are a few different articles or sites that mention daylilies as either xeric or water-friendly perennials.

https://extension.colostate.ed...
https://extension.colostate.ed...

https://extension.okstate.edu/...

https://www.gardeningknowhow.c...

@Lyshack Tim everyone can learn from discussion.

You have provided sources for sites that mention daylilies as xeric or water-friendly perennials. Two of the sites are associated with universities. However, none of the sites actually provide any evidence that daylilies are "xeric" or water-friendly. They simply list them as being so. Anyone can list something as being so. Simply listing it, no matter what the site or "authority" provides no reason to accept the statement.
We would need to find authoritative objective evidence that daylilies are xeric. That usually means published research. It also means that we would need to agree on what should be classified as "xeric".

To check that daylilies are adapted to moist conditions I checked published research on H. dumortierii. It tends to be naturally associated with moors and other moist locations. We can assume that it is adapted to those conditions. That it may be able to survive adverse conditions does not suggest that it is adapted to such conditions, other than to survive them. To be "xeric" I expect a plant that not only survives but thrives under low water conditions. Plants are adapted to survive some adverse conditions by avoiding them. They stop growing, lose their leaves, do not try to flower, etc. Tulips and daffodils are listed as "xeric" plants. But they avoid drought conditions by being dormant at those times. To be classified as "xeric" they would need to grow and develop normally when low water conditions occur at the time that they flower.

I consider that a plant is "xeric" if it thrives under low water conditions - that is, it grows, flowers, etc. without any added water - only what is provided naturally by the weather. The daylilies in my field do not do that. They may survive the occasional drought but they abort their scapes, drop their buds, etc. They are not xeric plants in my opinion and I have not seen any evidence that suggests that daylilies in general are capable of thriving under low natural moisture conditions. On the other hand, daylilies thrive and flower when grown in "water beds". They grow well and flower when in our pond. Are daylilies able to respond to drought periods to minimize damage and survive? Yes, but I do not consider that makes them xeric plants.

See below for an interesting article from Sunset on the origin and meaning of the word xeric. When I first got into daylilies I discovered that listings including them as drought-tolerant doesn't mean they actually like it. On the other hand, years ago a plant pathologist trying to find the cause of rot in daylilies discovered that while they didn't rot in his tests even when known pathogens were introduced, some cultivars did have roots that deteriorated when kept excessively wet.

The Sunset article about xeric:
https://www.sunset.com/garden/...

We seem to have wandered off from @Etophoj 's question, which may have nothing to do with moisture levels at all!