2021 Daylily Seed Growing Experiments

Can a Gardener Positively Impact Overall Germination and Growth of Daylily Seeds With Select Techniques?

There are numerous protocols and ideas for how one should handle and germinate daylily seeds. If you’re new to growing daylilies from seed, the conflicting and divergent information can be confusing, particularly as many methods are touted as being “better” or an improvement over some other established method.

Many growers talk about seed dormancy and various “stratification” and “scarification” techniques that some believe are required in order for a daylily seed to germinate. The mention of “stratification” can often put even veteran gardeners on edge; “stratification” seems to suggest some sort of technically difficult treatment that, if not done precisely right, will just result in failure. This leads growers to shy away from such “difficult” projects. My take is that growing daylilies from seed is nothing to be scared of. There are far more complicated seeds to grow (like orchids, which require a full-blown lab and sterile culture techniques)!

In 2022, as a novice daylily seed grower, I conducted several experiments to determine whether there was merit to some prevalent ideas regarding stratification and pre-treatment methodologies that are proposed as surefire ways to germinate daylily seeds. All of the seeds used in these tests were obtained from a wide range of seed sellers from the 2021 harvest season, and as such, they are already dried and refrigerated prior to receipt, which is standard practice, although the length of drying time an refrigeration must presumably vary. The seeds were also re-refrigerated upon arrival, and kept that way until being utilized.

I should also define a term that I use here to avoid any confusion; when I talk about “germination rate”, I am not talking about the speed at which seeds germinate. I am talking about the overall number of seeds that germinate out of a group of seeds, the ultimate goal being living seedlings vs. empty pots. Note, an albino seedling, while not ultimately viable, is still a germinated seed.

Spoiler Alert – based on the results, it is my opinion that the pre-treatments I tried were at best inconsequential, but at worst, even highly detrimental to germination rates. This seems to fly in the face of the currently established ideas surrounding daylily seed growing, given that all of the methods I tested were presented to me by various growers and resources as beneficial things I should consider.

A General “Control” Trial

Before going into the results of my experiments, one of the trials I ran was to replicate the experimental design but make no changes at all between trays. In other words, I attempted to find out how much natural random variation in germination there might be between seeds in a group. If the results varied wildly, then natural variation could potentially taint all the results of the experiments, rendering them useless.

In a side-by-side trial, splitting seeds of multiple crosses evenly into 2 trays, 45 seeds per tray all in individual pots, representing 14 unique crosses from 6 unique growers, the results were pretty remarkable. Germination rates in the first tray were 82% (37 seedlings), and 80% (36 seedlings) in the second tray. There was nearly no fluctuation for the individual crosses, which often had the exact same germination rate in both trays. Only 3 crosses did not see equal numbers of germination in each tray, and the differences were spread pretty evenly between the 2 trays, balancing things out.

In short, the experimental model seems to work. The same seeds, given the same treatment in side-by-side trays, germinated at effectively equal rates. This is just one experiment that leads me to the belief that germination rates of daylily seeds have much more to do with the specific cross and grower, and to some extent germination rates are already predetermined, “baked into” the seeds themselves.

Given the results of this control trial, I firmly believe that the results of the actual experiments outlined below are not random, but are absolutely impacted by the methodologies being tested against the basic protocol of just planting the seeds straight out of refrigeration.

“Cold Moist Stratification” on Perlite

Susan Bergeron’s Daylily Journal article, “Breaking Daylily Seed Dormancy with Stratification“, came up several times as I researched methodologies for germinating daylily seed. It paints a very convincing picture that the idea of “cold moist stratification” is beneficial for germination.

I’m going to insert a disclaimer here because when I first shared this still in a semi-draft state, a few experienced growers took this work as me either misunderstanding the concepts of “stratification” or somehow pointing to Bergeron’s work as somehow wrong. Neither is true. Specifically, this work sets out to answer the questions posed at the very beginning; does applying a cold-moist stratification period to refrigerated daylily seeds before planting them ultimately yield more seedlings to work with?

Specifically, “cold-moist stratification” represents the idea put forth by many online resources and discussions and is often framed against the idea that simply refrigerating the seeds, and chilling them for a period before planting, is not sufficient to cause them to break dormancy. As Bergeron writes, “Over the years, the ‘moist’ aspect [of stratification] has sometimes been overlooked resulting in disappointment for many who find that their dry refrigerated seeds don’t all germinate as quickly as desired.” I agree, in that many generalized discussions of “stratification” along a wide range of plants are really only talking about the chilling of seeds in storage.

The notion, as it relates to daylily seed, is that a cold and moist period is required to simulate natural winter and spring conditions, bringing the seeds into condition to germinate. As I pointed out at the start, there is a sea of suggestions on how to germinate daylilies seeds, and many of those sources point back to “cold moist stratification” as “the” way to do it. More to the point, when you chase it all down, most of this seems to be pointing back to or inspired by Bergeron’s work, which was in turn driven by the earlier work, in the 1950s, of Dr. Robert A. Griesbach. However, there are many growers who do not apply these methods to the seeds that they harvest or sell and yet grow plenty of seedlings, which of course, made me question whether the “cold moist stratification” was actually necessary or beneficial.

Bergeron’s article reports that refrigeration alone resulted in 60% germination, but “cold moist stratification” consistently yielded 97% germination in three unique substrate tests, and 93% on a fourth. Rich Howard also points to Bergeron’s methods as having a 95%+ success rate. These are significant improvements, and I set out to see if I would see comparable improvements in my own growing efforts. I think all of us would prefer 93-97% germination rate over 60%!

The methodologies outlined in this article were applied to 50% of the seeds from each cross. The result was that for each trial, two trays were side-by-side, one with seeds sown straight into the growing media, the other seeds first receiving a cold-moist-stratification treatment on perlite moistened with a solution of 1 tsp H2O2 (standard off-the-shelf 3%) into 1 cup of water (perlite first soaked, then drained of excess, before adding to seed bags) for approximately one month in the fridge prior to planting. The number of seeds in each run was not always 45; one trial ran with 48 pots crammed into each of the two trays. While the experiment was run six times, I’m excluding the first run, as I believe I overwatered the non-stratified tray and killed many seedlings, rendering the results invalid.

The results of the five successful trials were as follows:

  • Trial #2 – non-treated seeds -> 78% (35 seedlings), treated seeds -> 76% (34 seedlings)
  • Trial #3 – non-treated seeds -> 77% (37 seedlings), treated seeds -> 77% (37 seedlings)
  • Trial #4 – non-treated seeds -> 62% (28 seedlings), treated seeds -> 80% (36 seedlings)
  • Trial #5 – non-treated seeds -> 67% (30 seedlings), treated seeds -> 84% (38 seedlings)
  • Trial #6 – non-treated seeds -> 89% (40 seedlings), treated seeds -> 84% (38 seedlings)

The overall result from these 5 replicates resulted in 170 seedlings when seeds were simply planted immediately, vs. 183 seedlings when the seeds received this extra 30-day pre-treatment, out of 456 total seeds from 83 distinct crosses obtained from 6 hybridizers. Cumulatively, when seeds were simply planted, the germination rate was 74.5%; when seeds were first given the “cold moist stratification” treatment, that number rose to 80.2%.

The results bear out as statistically significant* at a 90% confidence level only if treated as a 1-sided test, but if I raise the confidence level to 95% or 99%, the results are not statistically significant. If we consider that the treatment could have negative results (a two-sided test) then the results we have are “not significant” at any confidence level (90, 95, or 99%). My opinion is that the notion that a pre-treatment with cold-moist-stratification in perlite improves germination success may have some mild level of validity, in terms of helping maximize the number of seedlings that are produced from a batch of seed. But it’s slim at best.

So, there is a trade-off here. My primary objection is that you’re delaying the start of growing by a month if you apply this cold moist stratification technique. This is a big detriment for me, a grower in the far north where the natural growing season is very short. Every extra month of growth I can put on a seedling before it is moved outside results in a larger, more robust seedling, and could even speed up its time to bloom. Is it worth delaying everything an entire month, just to maybe get an extra seedling or two?

Furthermore, when I look at individual crosses, it is clear that the overall majority germinated at exactly the same rate whether treated or not (remember my “control test” results?). And in some cases, the non-stratified seeds germinated at higher rates than those that were put through the treatment. Specifically out of 83 crosses, there were 12 crosses that saw better germination when their seeds weren’t stratified, compared to 26 that saw better germination when stratified. Contextually though, this could be the difference between 3 seeds in one tray sprouting, vs. 2 or 4 in another tray, in either direction. And these results, on their own, looking at just a handful of seeds from a single cross, are most definitely not statistically significant. It’s really not that far off from the natural variation I saw in the control trial outlined at the start of the article.

But the biggest number of all is the one where the treatment made no difference whatsoever in germination rates; 45 crosses, which represents 54% of the crosses in the experiment. In other words, more than half the time the treatment did nothing; and even more telling, the seeds germinated or failed in approximate parity across the trays. Whether 100% germination, 50% germination, or 0% germination, the results seemed to have a lot more to do with the specific cross, than the treatment the cross received, time and time again.

So, while overall there may be a very slight net positive to applying this type of cold-moist stratification, I believe that in most cases it is probably not worth the actual effort on seeds that have already been refrigerated. Only with the rarest/most expensive/important crosses, where maximizing germination of every last seed truly may matter, would I say “maybe you should try it.” Of course, based on my data here, I could argue that you have a 54% chance that the treatment does nothing, a 31% chance at improved germination, but also a 14% chance you actually harm/hinder germination!

Of note, the vast majority of seeds in the trial were tetraploid; there has been some suggestion that diploids benefit more from this sort of pre-treatment than tetraploids, so further experiments could be conducted. Turning my attention back to the first run of this experiment, the one where I think I overwatered and killed seedlings, that run happened to be all diploids, and the result was 1:2, with only 12 viable seedlings from the tray without stratification, vs. 24 in the stratified tray. I would have to replicate this experiment many more times with only diploid seeds to see if perhaps I’m misreading this experience, although at this time I stand by my assertion that I believe I overwatered the non-stratified tray early in growing, and rotted the seeds or killed seedlings via damping off and problems with fungus gnats.

As I look at 2023’s seedlings, so far I’m having no problems with diploids coming up, which bolsters my opinion that the first trial was a failed run, and not some indicator that things are different for diploids. So, for now, I am not wasting my time with cold-moist stratification in the fridge! I’m simply storing my seeds as they arrive or as we package them in a refrigerator, and planting them straight in the substrate when I’m ready to start them. I am happy with the results I am seeing. But, I have been convinced to try more tests again this year.


Relating to this idea that cold moist stratification is required to break dormancy, in 2022 I emptied every failed seedling cup, sifting through the substrate in search of seeds. I wanted to figure out whether the seed had failed and rotted away, or was still present, firm, and potentially still viable. This generally occurred after about one to three months, at which point germination rates in the trays had plateaued, and no new seedlings were showing up.

Most of the time, I found either nothing, or the hollowed-out, crumpled, or broken remains of the shiny outer black shell. A few times, seeds were found that were in the process of rotting away, oozing their interiors with the slightest touch.

However, when I found a pot with a potentially viable seed that remained solid when slight pressure was applied, the seed was replanted in the substrate and the pot was placed in our refrigerator. It was chilled for a period of at least 30 days, sometimes significantly longer. The media in the pot was moist at the time of placing it in the refrigerator, but no further water was offered.

Eventually, the seeds were returned to growing trays under lights at room temperature, watered, and given a second chance at germination. Out of well over 100 seeds that received this treatment, I ultimately saw just 7 seedlings emerge, so let’s call it generously 7%.

But, also, it bears consideration that I threw out several hundred pots where seedlings had clearly failed along the way. If you factor those failed seeds into the mix and ask the question “are there any viable seeds still here in all these empty pots?” then the answer seems more important. After a couple of months, out of several hundred pots that failed to germinate on the initial run, there may have only been 1-2% of all those pots that held seeds that had yet to sprout.

The take-home message was clear, from my perspective. Whatever seeds were going to germinate were most likely to do so in the first month, and pretty much the fate of nearly every seed would be known at the end of two months, at least in our seed-growing setup. Trying to reapply a second round of “cold moist stratification” in this manner could get you that miracle seedling you were hoping for out of a particularly important cross, but overall the return on investment of time and effort is extremely low. So, it is my suggestion that you “restratify” your still-dormant seeds only if you have the space, and if every last seedling from that particular cross may matter.

“Soaks” and “H202 Scarification”

There are suggestions out there that encourage the soaking of daylily seeds prior to planting them since they have been generally stored in a dry state. There are also suggestions that treatments that include hydrogen peroxide (H202) solutions can help to chemically “scarify” the seed (which means breaking down the seed’s hard outer coating, encouraging germination). I found a protocol that came highly recommended, so I put it to the test. The hope is that the treatment will result in more seeds germinating leading to a greater yield of seedlings.

3/29/23 – I should note now that an earlier draft version of this article included significantly different reviews of the results. I discovered, upon rechecking my notes, that I had not conducted three series of test runs that were all the same. While my overall opinion of the results remains unchanged, I’ve updated the data reporting and analysis appropriately.

To test the hypothesis, I split seed lots from a wide range of grexes (crosses) evenly, placing half into a soak of 1 tsp 3% household H2O2 to 1 cup of tap water (our’s is very soft, 43 TDS out of the tap, wonderful Lake Superior water), and held at room temperature (approx. 69F). The other 50% of the seeds were left to sit out, dry, during the duration of the soaking period for the treated seeds, and they were then simply planted directly. Each seedling tray held 45 pots, with 1 seed in each pot. Each pair of trays was placed on the same shelf, side-by-side in the middle of a shelf on a growing rack, to provide the most homogenous light and heat conditions possible.

The results of the two experimental runs, which I’ll call Group A, were as follows:

  • Trial #1 – non-treated seeds -> 82% (37 seedlings), treated seeds -> 71% (32 seedlings)
  • Trial #2 – non-treated seeds -> 62% (28 seedlings), treated seeds -> 51% (23 seedlings)

A third experimental run was conducted, but the treatment was different, based on feedback from another grower who suggested a different concentration of H2O2 and a longer duration of soak. In this series, the ratio was 1:10, H2O2 to water, and the soak duration lasted 7 days. Again, the non-soaked seeds were left sitting dry, at room temperature, alongside the soaking seeds. During this timeframe, many of the soaked seeds actually germinated while still being soaked. The results of this third run, which I’ll call Group B, were:

  • Trial #3 – non-treated seeds -> 56% (25 seedlings), treated seeds -> 29% (13 seedlings)

Adding these all up, the collective numbers are pretty stark. Overall, exactly two-thirds, 66.67% of seeds, germinated with no soak+H2O2 pre-treatment. When seeds were put through various treatments, collectively only 50% germinated. However, not all seeds were put through the same treatment.

Looking separately at the two different concentrations and soaking periods, Group A had 72% viable seedlings from unsoaked seeds, vs. 61% in treated seeds. Despite a larger sample size, the results do not calculate as statistically significant at the lowest generally available 90% confidence level (however, recalculating with more robust tools and then using a second calculation, the results would be considered significant at an 88.45% confidence level; just one seedling difference would have been all it takes to hit that minimum 90% threshold. Confused by confidence level? There’s an easy-to-understand explanation here.).

In Group B, there were 55% viable seedlings in untreated seeds, vs. 29% in treated seeds. While the sample size is small, the result calculates as significant to the 99% confidence level.

I’m inclined to say that while not 90%, an 88.45% confidence level is still likely sufficient to conclude that the shorter, milder soaking treatment (Group A), didn’t increase success and actually caused harm. It collectively lowered the final seedling count from 65 down to 55 (72% vs. 61%), and throughout my experiences raising seeds, germination rates of the same cross across multiple trays tend to be pretty similar when all else is the same. Mathematically, if the results remained similar across a larger sample size, they would hit the threshold where they would be statistically significant at 90%, then 95%, and so forth. As such, I find myself asking “do I risk more seeds with this treatment just to prove the point?” My answer is no.

Without a doubt, the longer, stronger treatment appeared to cause greater harm, reducing the final seedling count from 25 down to just 13 (56% vs. 29%).

So, if you want to grow fewer seedlings, by all means, soak your seeds in a dilute H2O2 solution prior to planting. Don’t say I didn’t warn you!

But it gets worse! Separately from these trials, I ran substrate trials to see if the type of growing medium had any bearing on seedling growth and health. In preparing for some of those trials, entire batches of seed received the same soaking methodology (all seeds of the cross were treated, to rule out any variation from the pre-treatment). In these soaks, I utilized the same methods outlined for Group B (1:10 ratio of H2O2 to water, approximately 7 days soaking at room temperature). Replicating this treatment, which came to me as highly recommended by a veteran seed grower, proved extremely detrimental in my opinion; 4 out of 11 crosses failed entirely, resulting in zero seedlings regardless of the substrate. In this instance, tetraploid seeds seemed to tolerate and survive this long soak treatment better than the diploid seedlings were only 3 out of the 7 diploid crosses surviving at all.

Furthermore, considering the outcome of these “soak until there are germination” efforts, I continue to struggle with the methodologies that encourage germinating seeds prior to planting, particularly once they have their initial tap root. It is very easy to simply break that root and doom an otherwise viable seedling. Why take that risk just to “see” that the seed has sprouted? Simply putting the ungerminated seed into a substrate and waiting allows the seed to do what it is genetically programmed to do, growing naturally, without risk of mechanical damage at its earliest stages of life.

The moral of the story—do not soak your seeds in a solution of H2O2 as outlined here, as the protocol is absolutely detrimental. I see no upside whatsoever. Is there an H2O2 methodology that works, and maybe improves germination? Perhaps. But the ones I tried do not.

Substrate Trials: Does Substrate Matter?

When researching daylily growing in containers, there is no shortage of options for potting media, including some that sound very peculiar. Every media has its advantages and downsides, and it should come as no surprise that many people seem to prefer whatever it is that they’re using. Then again, the media a grower uses may also be a direct reflection of the cultural methods that the grower is applying.

When it comes to seed-starting and early growing of daylilies under lights indoors, one of the more interesting suggestions that came to my attention in 2022 was the use of coco coir (coconut pith fibers). Coco coir is considered a renewable resource and is generally available in a very compressed brick that you have to hydrate to break apart. The quality and properties of the product can vary widely, and often times there are recommendations to soak the coir prior to use. So, it’s a little more labor-intensive from the get-go. It also may not be any more or less expensive to use. But commercial houseplant growers have switched to using it in certain applications, and there are some legitimate reasons to consider it. However, it is also a bit inert and lacks much in the way of the nutrients plants need, which elevates the need for fertilizing. Ultimately though, I certainly had to consider coco coir based on the sustainable nature of the product.

I ran many trials using four variations on the substrate for seed starting. My default preferred mix is a 2:1 ratio of ProMix (peat-based) with coarse perlite. In addition, I tried straight ProMix without added perlite, straight coco coir (Coco-Bliss brand), and a 2:1 ratio of coco coir to coarse perlite. I utilized “long-cross” groups of seeds when possible, with the hopes that there would be several pots of each substrate utilized by the crosses. The seeds and substrates were equally distributed in the growing trays, with their positions in the tray randomized with help from an online randomizer.

There were two questions to consider; did the substrate impact germination rates? The answer appears to be no. However, as noted in the section on H2O2 pre-planting soaks, several of the large groups of seeds failed entirely, so many of the test results were probably not valid as a result of the pre-treatment and the negative impact it had. Later trials without pre-treatments on seeds were not much more conclusive.

The second question, which was the main focus of these experiments and yet harder to quantify; did the seedlings grow any better in the coir substrate? Unfortunately, the answer is highly subjective, but if anything, I think the ProMix + Perlite mix edged out the other variations; seedlings just seemed to be huskier and happier.

Going beyond the initial timeframe of the trail, and looking more at long-term viability, once the seedlings were outside, but still in trays in their individual pots, I found the seedlings in coir were the first to dry out, and this resulted in more stressed seedlings and even some losses. ProMix+coarse perlite seemed to retain moisture better, but also allowed the roots to breathe while the pots were bottom watered with fertilizer. While no official data was collected on this, my gut feeling is that ProMix + added perlite was the best option out of the four variations that were tested. This is certainly an area open for additional experimentation.

Future Experiments

While it seems like I’ve found a seed-growing protocol that works here well, there is always room for improvement. More than once, I wrote above that there is room for further experimentation. There is also room for intrepid seed growers to attempt to replicate the experiments I’ve presented, to see whether my results are repeated, or if different outcomes are discovered.

Seed-growing customers have already sent examples of methodologies that appear downright foreign to me, yet seem incredibly interesting and even enjoyable. There is certainly no one right way to grow a daylily seed.

One aspect of growing and germination that seems worthy of future investigation is whether bottom heat helps germination. Seed starting mats are widely available, and it seems to be commonly understood that for many seeds, the heat source absolutely helps.

As it pertains to our seed-growing efforts, my growing racks are five shelves high. The top four shelves all have a LED light underneath. That LED light is generating heat. The bottom shelf has no light underneath, and thus, no bottom heat. In 2022, growing seeds from the 2021 harvest, it “felt” as though trays on the bottom shelf, or those placed elsewhere in the room where there was no heat source underneath, either germinated more slowly or at lower rates. Possibly both.

I am already seeing anecdotal evidence of this effect in my first seeds from 2023, where trays started just a day later on the bottom shelf only have a handful of seedlings above ground, yet trays a day earlier and a row above (with a heat source underneath) already show as much as 33% germination at roughly just 10 days in!

“Feelings” and “suspicions” are a great source of inspiration for experimentation, and proper inquiry may either disprove those gut feelings or prove them and reveal important findings that can benefit a daylily seed grower’s experience. Investigating the role of bottom heat in daylily seed germination is one of those tests that I will likely run in 2023, given that I not only have ample seeds to test with, but also temperature loggers that can accurately quantify the difference between a seedling tray on the bottom shelf compared to a tray just a couple of feet higher on the rack with a LED light radiating heat underneath! This experiment will likely require intensive tracking of germination rates to properly capture the effect of bottom heat.

This year I came across the suggestion that a top dressing of cinnamon may help eliminate fungus gnats. In the past, I’ve used Mosquito Bits when bottom watering to control them, along with yellow and blue sticky cards to lure and detain adults. Interestingly, in the first month of seed growing with top-dressed cinnamon, I’ve seen almost nothing in the way of fungus gnats, and my new sticky traps have captured next to nothing. Is it simply a bad year for fungus gnats, have I gotten better at applying the appropriate amount of water to my seedlings, or is the cinnamon really having an effect?

Many sources cite the use of cinnamon as a proven methodology, but they differ on the reasons behind why it works. Most seem to say that cinnamon powder has powerful anti-fungal properties, and thus deprives larval fungus gnats of their preferred food source. An added bonus may be that it helps prevent damping off as well. This all may be true, but it raises other questions. Part of the reason to use ProMix is the beneficial mycorrhizae (fungus) present in the mix; does the application of cinnamon counteract that? Furthermore, in older trays I’m finding the cinnamon powder is, itself, growing some fungus! Fewer references suggest that the aroma of cinnamon is a powerful repellent, so the flies avoid the trays in the first place due to the delightful smell. Clearly, these are all questions ripe for investigation, and some properly designed experiments could reveal interesting results.

Another seed-growing question that simply demands an answer centers around the photoperiod utilized to grow daylily seeds. How long should you illuminate a daylily seedling growing under lights? 12-hour, 16-hour, or 24-hour lighting? Even at a more basic level, it seems people disagree on whether 24-hour lighting of plants can even work or not, some arguing that certain essential biochemical processes can only occur in darkness.

While there may be some plants that require a dark period, I’ll tell you now that many plants grow just fine with constant illumination, including daylilies. But is 24/7 illumination any better than a shorter lighting period (which, if nothing else, costs less from an electricity standpoint)? Testing a question like this requires a more intensive approach to experimental design, but the effort may provide very useful results. Perhaps you’ll be the one to set out on the journey to reveal the truth.

*Calculations of statistical significance were primarily made via a simple online calculator for A/B testing, allowing for both one-sided and two-sided considerations, at 90%, 95%, and 99% confidence levels.

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