Ginseng Seed Dormancy & Delayed Germination
...in Plain English
April 30, 2016
Well, mostly plain English. It is difficult to address issues of plant science without using the proper scientific terms at some point, so we will get that out of the way first. Most seeds fall into one of five different types of dormancies. There are physiological, morphological, morphophysiological, physical and combinational. Of these, morphological is commonly attributed to ginseng. However, ginseng also has some traits of the morphophysiological dormancy.
Now we will start to work in the plain English part.
Morphological dormancy generally means that the seedling embryos are not fully mature when the seeds/berries become ripe. This is the reason the seeds of some plants (like ginseng) planted in the fall after ripening do not germinate the following spring. The embryo inside the seed needs to mature more before it is ready to germinate. This is sometimes called after-ripening and is the trademark of morphological dormancy.
Morphophysiological dormancy is even more complex. But, we couldn't get lucky enough to leave it there. Ginseng might be best described as having deep simple double morphophysiological dormancy. In plain English this means the seeds of American Ginseng require a cold, warm, cold, warming temperature sequence to break the dormancy. However, there are many aspects which affect this task. Genetics of the parent plant and the environmental conditions are very important for successful germination in ginseng.
Before we move on, let's go back and consider that the reason for dormancy of seeds in the first place is to ensure survival of the species. Doing so gives us a very good overarching point of view from which understanding dormancy becomes much easier. Let's start with the basics.
There are two major types of plants -annuals and perennials. Annuals are the bedding plants you buy every year to put in the flower beds around the house, or most of the vegetables you grow in the garden. You buy seeds or plants every year and plant them in the spring because they cannot survive cold temperatures. One of the more common annual plants would be a tomato. You plants seeds or started plants into the garden in the early spring when danger of frost is past. The plants grow well in warm weather with adequate moisture and nutrition. By midsummer you start harvesting ripe fruits, but the fruit keeps coming and eventually so will a killing frost in the fall. The fruit and the vines they are on will be destroyed overnight by a frost. Within each fruit is typically some viable seed. If Indian summer kicks in and it remains warm for a while after that first frost, some of those seeds may actually germinate within a few days and produce small tomato plants. However, they are certainly doomed to die when the next frost comes and they have not had time to produce fruit.
Perennial plants are a completely different animal. First, they can survive from one year to the next. Secondly, you generally plant them in the fall, not the spring. Think of tulips, crocuses and other early spring flowers that start to show up as soon as the snow is gone in the spring. You might also consider woodland plants like mayapple. Planting in the fall is especially important to ginseng because ginseng starts to germinate early in the spring. Once it starts to germinate, you cannot readily transplant it without killing the baby plants. Unlike tomato seeds, ginseng seeds will not germinate anytime the environmental conditions are suitable for the seeds to sprout up. This is known as dormancy.
One way to conceptualize dormancy is like a lock on the seed germination which protects the seed from germinating at the wrong time of year. Dormancy keeps the seed from germinating until the proper key (temperature sequence, time, and environmental conditions) are presented. This keeps ginseng seed from sprouting in the fall when there is not enough time to grow a large enough root to support the emergence of a top the following spring. Generally, seedlings that sprout in the spring will have attained regenerative ability by mid July. So, basically, it takes about three months for seedlings to reach the point where the tops can die back (senesce) and there will be enough root and a bud there to send up a top the following spring.
So, berry ripens, gets put into sand for a year, taken out and planted and they germinate and emerge the following spring -right? Right -mostly. The berries ripen but the embryo is not yet fully matured (as indicated by morphological dormancy). Then, by going through the fall and winter (cold), summer and fall after that (warm), and yet another fall and winter (cold) we have satisfied the requirements of deep simple double morphophysiological dormancy -mostly.
If we are looking at this from the prospective of protecting the survivability of ginseng as a species -the reason for dormancy in the first place- we can accept what we cannot change a little easier.
We know that every spring is not ideal. A few years back we had a very hot, dry, early spring. This was not good for ginseng as many of the plants that came up early were subjected to a cold snap which damaged the flower stems of the plants. This was the reason for the huge jump in ginseng seed prices the following year by the way. But think about this for a second. We have a seed which is designed to stay dormant for over a year normally even in ideal conditions. Does it make sense that the mechanisms which keep that seed from germinating at a time of year when it cannot survive (dormancy) would allow it to germinate at the right time of year when conditions are such that the resulting plant would not have a good chance to survive? Say we have a hot, dry spring, is there a good chance that newly emerged ginseng plants will make it long enough to ensure survival over the following winter? Not really, no. This is commonly referred to as delayed germination, secondary dormancy, or double dormancy.
As humans in today's society, we tend to conceptualize time as a tangible commodity. This is why we get upset with the delivery guy who says he will be there either morning or afternoon without narrowing those options. We feel like we are wasting time just waiting. But, ginseng doesn't care a bit about that. This is a perennial plant that commonly will not even produce any seeds in the wild until it is four or more years old. It feels no time pressure what so ever. None. So, from that perspective, the survival of the species is of paramount importance regardless of the time it takes. Said another way, if the conditions are not ideal when the primary dormancy is satisfied, it makes sense to the ginseng species to simply wait until next year. As humans, we want to set our clocks -ripe berries in the fall, stratification winter and summer, planting following fall, germination following spring! But, it just doesn't always work out that way.
Hopefully, we are starting to understand a little better why this happens by this point. Survival of the species is the most important aspect, and the nature of the dormancy is designed to ensure that survival. Consider something going wrong during stratification. Maybe the seed gets too hot, or too dry. Maybe the dormancy mechanisms interpret this as a drought which might endanger newly germinated ginseng plants. From this perspective (survival of the species), the best course of action since the seed is designed to lay dormant, is to hold off germinating until the next spring in hopes that conditions will be better then.
I've said all that to say this -ginseng dormancy is incredibly complex when we really think about it. Any number of things (and we didn't even discuss genetics here) can affect the dormancy and resulting germination of ginseng seeds. Years ago we all put them in the refrigerator until we planted them. Don't do that. There seems to be some connection between delayed germination and seed held in the fridge and then planted before the ground temps are as low as the temperature where the seed has been held. Moisture is another factor. We used to believe (and many still do) that a dry ginseng seed is a dead ginseng seed. We know now this isn't really true. Ginseng seed can stand to be held (particularly in stratification) much dryer than we had thought possible before. As long as the seed maintains consistent, minimal moisture in the sand it will be fine. However, inconsistent moisture can cause issues with germination.
So, let's apply this to the real world. You buy seed from a known dealer who tells you the seed has been stratified and viability tested in the low to mid 90s. Remember, we cannot do a germination test on ginseng. We do a viability test which shows the percentage of seed that is alive and viable (through respiration). You plant in a good spot the day you get the seed. And then next spring you get out there and don't see anything. You wait and go back a week or so later and you still don't see anything. Finally, a few weeks later you see two or three small ginseng seedlings where you planted thousands of seeds. What happened?
Well, the uneasy answer is that we just don't know. What we do know is that it is not likely your dealer intentionally cheated you. In years past delayed germination has been associated with mixing of green seed with stratified seed. The best I can determine this falsehood originated in a book where the author suggested green seed costs half as much as stratified seed. The suggestion being that if you pay your dealer $100 a pound and it costs him $80 for stratified seed but only $40 for green seed, for every pound of green seed he would mix in he is saving $40 in costs. This lie has been passed on from grower to grower ever since. The fact is that the cost of ginseng seed is in the harvest and processing, not storage. Once green seed is picked, depulped, sanitized, mixed with sand and placed in the stratification boxes, there are no additional labor costs until it is moved from cold storage to open air in the spring. That cost is very minimal compared to its initial processing. Therefore, the fact of the matter is that green seed costs as much to a dealer as does stratified and float tested seed does. There is just no incentive for a dealer to mix green and stratified seed. There is also absolutely no reason for a dealer to intentionally cheat his or her customer either. None.
In today's world, logistics is a big issue. We often ship things through huge organizations over which we have no control once our product is in their hands. This is a good place for the old joke about marking boxes as fragile means they get thrown underhand instead of overhand. The case gets more complex when we include shipping an item like ginseng seed which is susceptible to changes in environmental conditions.
Now it is time for a story. A couple years ago I had trouble with the shipment of my ginseng seed. I have never hid the fact that the seed I plant and sell to others comes from a very reputable family farm in Ontario. To cut to the chase, UPS dropped the ball on this one. Period. The necessary paperwork was in place and the seed was shipped. However, when US Customs inspected the packages of seed the paperwork was missing. As we know now, a UPS employee removed the paperwork, scanned it into the UPS system, but did not replace the paperwork in time for the Customs inspection. As a result the entire shipment was refused entry into the US. To make matters worse, it was discovered that the boxes of seed were shipped from the Customs warehouse anyway, and was actually on the local truck for delivery when it was recalled. That means it sat in a big brown truck on a hot day all day, and then was shipped back to the warehouse in Detroit. It took me about a week on the phone to figure out what had happened. A duplicate set of paperwork was created by the Canadian Ministry of Agriculture and sent over night to the warehouse. It took UPS several more days and numerous calls to the supervisor before the seed arrived a week later -after another all day sit in a big brown truck on a hot day. The seed was very dry when it arrived.
Now, it is not uncommon at all for ginseng seed stratified under controlled conditions above ground to float when it comes out of the stratification boxes. Growers typically leave it in water overnight to hydrate then after a good mix, scrape off the remaining floaters. I hydrated the seed until it all sank (overnight) and checked it well. All the seed was good, and the grower had it viability tested at 95%.
Fast-forward to the next spring. Last spring was late. All the talk in the ginseng circles was that germination was spotty at best. I fielded several calls from my customers asking when to expect to see the seedlings emerge. Eventually, it came to the point that it was obvious they just were not going to germinate. I had three heavily seeded beds at the house in which a grand total of four seedlings emerged. Four. I was unhappy of course and talked to the grower who advised they were experiencing very good germination. I had not handled the seed any differently once it arrived to me, so the difference was in the time stuck in Customs where I had no control over the conditions. Normally, the seed gets to me within three days of shipping.
Another important point to consider is that many perennial plants share similar characteristics in regard to their susceptibility to environmental conditions. As I was driving this morning I was listening to the gardening show I like (Ron Wilson on WTVN in Columbus). It became apparent by the discussion that many people had issues with morning glory plants last spring. They didn't seem to bloom on time, and when they did finally bloom the blooms were few and far between. This was not at all a typical season for these plants. As the discussion went on, the cause was assumed to be environmental as similar issues were widespread with forsythia plants. The blossoms that did appear were few and late in the season. Ron said that he believed there was something about last spring environmentally because of the wide spread issues with these different plants. Perhaps this environmental mix-up also contributed to the delayed germination of the ginseng seeds.
As you can imagine, some folks got mad at me, some publically jumped on forums and called me all sorts of names and even called for my banishment from the ginseng community. Naturally there was nothing I could say in return other than ginseng dormancy is very complex and the seed I'd dug up and tested was still good, viable seed. In fact, even in the best of conditions in years with outstanding germination, delayed germination is still present. As of right now, I have seedlings coming up in a bed where seed hasn't been planted the last three years. That means this seed was planted in fall 2012, stayed dormant through a year with outstanding germination, a year with very good germination, a year with little or no germination, and now this spring decided to germinate.
Notice these seedlings among a bed of three-year-old plants
The picture at the top of the page shows a bed of two year SELECTs where a thousand roots were dug in such a way as to separate the bed to help control disease should it occur. As you can see clearly in this picture, it looks like I reseeded this spot. But, in fact, those are all seeds which did not germinate on time, but rather delayed a year -even though germination was outstanding the year prior. The next year, the entire bed was emptied and goldenseal was planted back. Now, the second spring after planting the goldenseal, I'm still seeing ginseng seedlings emerge from that bed.
I knew the 2014 seed was still good. It just didn't come up on time. It would seem that no one is exempt from the whims of this mystical plant.
I anxiously awaited this spring and hoped and prayed for good weather. About a week ago I began seeing some of the plants emerging from the beds. As I looked closer, I saw some seedlings emerging. We have been having some rather cool weather, so germination is slow, but enough of the seedlings in the beds planted the year prior have emerged to prove the seed was indeed good seed all along, and in fact, even with the mice getting into the beds, the germination looks pretty good.
These pictures show a bed that was planted with the 2014 seed. Even though
seedlings are still emerging, it is clear the seed remained healthy and viable
even though germination was delayed a year
When I was young it took me a long time to learn that if I wanted to grow ginseng I had to do so in the manner in which the ginseng wanted to grow. That is I couldn't plant it in a sunny spot and keep it watered heavily and expect it to survive. I learned that I had to grow ginseng in conditions it chose. I could plant it behind tall ferns or under shade cloth as a substitute for the mature hardwoods, but ginseng requires that the surface of the plant be kept cool -normally by the effects of shade.
Last spring many folks learned that first part of a two-part lesson about ginseng. The first part is that no one is exempt and sooner or later something will happen that will cramp our preferred style. Delayed germination happens to everyone, but some years it is much more noticeable than others regardless of our efforts. The second part of the lesson is coming this spring. Just because ginseng seed doesn't germinate at a time of our choosing, doesn't mean the seed was bad or that a dealer has cheated you.
That ginseng seed is designed to lay dormant for so many years to ensure the survival of the species is a miraculous thing to me. As a friend often says, just when you think you get ginseng figured out, it is sure to show you that you don't. Therein lies a third lesson. This lesson is that ginseng has survived longer than people have been growing it. We may be able to manipulate the plant to some degree, but ultimately, sooner or later, deep simple double morphophysiological dormancy will rear up to bite you. With that knowledge, we need to just pull up our big kid panties and smile about how wonderfully mystical this plant really is.
Update May 16, 2016
I took those pictures and wrote this article on the 30th of April. The seedlings in that bed had been coming up slowly (we had some very cool weather here) for about a week. Well, it is now the 16th of May and they are mostly up. This will give you a better idea of how good the germination really was in this bed despite mice, chickens and such for a year.
Notice this bed has filled in and the seedlings have spread out in two weeks
In addition, it is important to also understand that genetics pay a role in seedling germination. While the seedlings which were delayed arrived about when they were expected (even though they came up slowly over a couple weeks), some of the seed I've planted last fall from other strains are just now starting to come up. We have had some more cold weather, and it was in the low 30s here the last couple nights. The seedlings in this next picture are from seed gathered from transplanted wild stock. In my experience, wild Ohio seed germinates and comes up later than seed from other areas. I've tried seed from New York, Wisconsin, West Virginia, and of course Ontario Canada, but wild Ohio seed germinates later than them all.
Wild Ohio seedlings just emerging on May 16, 2016