“I Planted Them, So Why Haven’t They Come Up?”
There is something slightly magical about planting a seed.
You put a tiny, apparently lifeless object into some soil, give it a little water, and wait for a plant to appear. Most of the time this works well enough. Sometimes, however, nothing happens.
You wait a few days. Then another few days. You start wondering if you did something wrong. You water them again. You move the pot somewhere warmer. Eventually you decide the seeds must have been bad. Then, just when you have given up and planted something else in the pot, a tiny seedling appears. I have had this happen more times than I can remember.
Some seeds germinate almost immediately. Others take weeks. Some seem to need a particular temperature, some need light, some need darkness, and some need to experience winter before they are prepared to grow.
I have also had seeds germinate well after I had decided they were probably dead. Seeds that sat in the garden for years before appearing, and seeds that spent months in the fridge before finally deciding it was time to grow.
The important thing to remember is that failure to germinate does not necessarily mean failure of the seed. Sometimes the seed is dead. Sometimes it has been damaged by poor conditions. But sometimes it is perfectly viable and is simply waiting for the right signal. Understanding why seeds behave this way can make growing from seed considerably less frustrating.
The Things Every Seed Needs
There are a few basic requirements for germination: a viable embryo, water, oxygen, a suitable temperature, and, for some species, particular light conditions.
The first one is obvious but easily forgotten. A seed needs to be viable. If the embryo inside has died, no amount of careful watering or temperature control will bring it back.
The other requirements are more interesting because different species have different preferences.
Seeds need water to start the germination process, but they also need oxygen. A seed sitting completely submerged in water is not necessarily happier than one sitting in moist soil. In fact, excessive water can cause many seeds to rot before they germinate.
Temperature is also important. Seeds generally have a range of temperatures in which they germinate best, and that range varies considerably between species.
Light is another variable. Some seeds germinate better with light, some prefer darkness, while many species don't seem particularly bothered either way.
This is one reason I don't like making sweeping statements about germinating seeds. There are always exceptions. The instructions on the seed packet are there for a reason.
Is the Seed Dead or Dormant?
Seed dormancy is one of those things that sounds complicated until you think about why plants would have evolved it.
A plant that dropped all its seeds and had them germinate immediately would not necessarily be very successful. Imagine a plant producing seed at the end of summer, with all of it germinating just before winter. The resulting seedlings might be killed by cold weather before they had a chance to establish. It makes much more sense for some plants to have seeds that wait.
Dormancy allows seeds to delay germination until the conditions are more favourable. The exact mechanism varies between species. Sometimes the embryo needs time to mature. Sometimes the seed coat prevents water entering. Sometimes chemicals within the seed inhibit germination. Sometimes the seed needs to experience a particular environmental cue such as light or temperature before it will germinate.
This means there is a big difference between “this seed won't germinate” and “this seed won't germinate yet.” That distinction has saved me from throwing away quite a few batches of seed over the years.
Some Seeds Need To Experience Winter
For some plants, winter is part of the germination process. If a seed comes from a plant growing in a climate where a harsh winter reliably follows autumn, it can make sense for the seed to have a mechanism that prevents it from germinating as soon as it hits the ground.
The seed may sit through the cold, wet months, and only become capable of germinating once spring arrives. In the garden, we can let nature do this if we are in a temperate climate. Sow the seeds at the appropriate time, leave them outside, and allow winter to provide the necessary conditions.
That works, but it isn't always convenient. If you are trying to grow a small number of valuable seeds, waiting six months to discover whether they germinate can be frustrating. It is also difficult to control exactly what happens to seeds sitting outside. This is where cold wet stratification comes in.
Cold Wet Stratification Explained
Cold wet stratification is essentially a way of giving seeds an artificial winter.
The important word here is cold, but the other important word is moist. Simply putting a packet of dry seeds into the refrigerator is not the same thing as cold stratification. I have seen this mistake surprisingly often.
For cold wet stratification, seeds are normally exposed to cool, moist conditions for a period appropriate to the species. A refrigerator can be used to provide the cold part, while damp paper towel, vermiculite, sand, or another suitable medium provides moisture.
My own method is fairly simple. I soak the seeds in water, then put them onto damp paper towel in a labelled zip-lock bag, and place them in the refrigerator. I don't want the paper dripping wet. Seeds need oxygen as well as moisture, and an excessively wet environment is an excellent way to encourage mould and rot.
Labelling is important too. I have a tendency to forget how long things have been in the fridge. A label with the plant name and the date saves a lot of confusion later.
The length of stratification varies enormously between species, so this isn't a case where longer is automatically better. Some seeds need only a short period of cold, others need several months, and some may need more than one cycle.
One of my more extreme examples is black raspberry. I grew these from seed after giving them well over three months of cold wet stratification. Some actually germinated after much longer periods, and even after doing everything correctly, some seeds didn’t germinate until the following year when they had experienced one ‘winter’ in my fridge and a second winter in the yard.
That is one of the recurring lessons of seed growing: a recommendation is a starting point, not a guarantee.
Breaking Through A Tough Seed Coat
Sometimes the problem isn't that the embryo is dormant. The problem is that water can't get to it.
Some seeds have very hard seed coats. This can be an advantage in nature because the seed can survive for a long time without germinating, but it can be inconvenient when you are trying to grow the plant in a pot.
One way of overcoming this is scarification. Scarification simply means damaging or weakening the seed coat sufficiently for water to enter. Depending on the size and type of seed, this might involve carefully rubbing it with sandpaper or nicking the seed coat or even soaking in a mild acidic solution such as vinegar.
The idea isn't to damage the embryo. You are just trying to make a small weakness in the outer coating. Nature has plenty of ways of doing this. Seeds may pass through an animal's digestive system, be weathered by moisture and temperature changes, or even be exposed to fire.
Which brings us to another interesting treatment.
When Hot Water Helps
Hot water treatment is another way of weakening the protective coating of some seeds.
This is particularly relevant to some plants from fire-prone environments, where heat from a bushfire can naturally damage hard seed coats and allow water to enter.
Some Australian native seeds respond well to this treatment, particularly members of the pea family. It isn't something I would recommend trying indiscriminately, though. Seeds vary, and a treatment that helps one species can damage another.
I have had some interesting experiences with seeds that looked as though they should be difficult but turned out to be surprisingly straightforward once their protective structures were dealt with.
Canna lily is a good example. The seeds are round and incredibly hard, they are more like pebbles than seeds. I had read all sorts of stories about how difficult the seed was to germinate. I put 10 seeds in a bowl, tipped almost boiling water over them, they made a horrible cracking sound and I thought I had killed them. I allowed the seeds to soak and cool overnight, and planted them. All 10 germinated in a little over a week.
That doesn't prove that every canna lily seed should be treated in exactly the same way. It does demonstrate something I have found repeatedly with seeds: sometimes the difficulty is not where you expect it to be.
Before applying a hot-water treatment, check the requirements for the particular species. Do not assume that because a plant is native to a fire-prone area its seed always needs boiling water.
When Seeds Need Smoke
Smoke is one of the stranger things to encounter when you start looking into seed germination. For some Australian plants, it turns out that smoke contains chemical signals that can help trigger germination. Fire is an important ecological event, so for certain species, smoke can act as a signal that conditions following a fire may be suitable for new plants to establish.
Research has shown that smoke can promote germination in a wide range of Australian native plants, including species that can otherwise be extremely difficult to germinate. Smoke-derived compounds such as karrikins are involved in this process.
This doesn't mean that you should set fire to your seed trays!
There are safer ways of providing smoke related cues, including commercially prepared smoke products and smoke infused materials. Smoke water has also been used for some species.
It is important to use the treatment appropriate to the species. More smoke is not necessarily better. Excessive concentrations can actually inhibit germination in some plants.
For the home gardener, the most useful lesson is probably simply to recognise that some seeds have evolved to respond to very specific environmental signals.
You can buy commercial smoke water products, but I have always used the DIY version. I burn a small amount of twigs and leaves from native plants from my yard, and collect the ashes. I soak in water for 24 hours, sieve, and use the smokey water to soak my seeds before planting, and then for the first few waterings. I have tried smoke treatment for Xanthorrhoea (grass trees) and a few other native plants, and find it generally results in high germination rates.
If a packet tells you that a native plant needs smoke treatment, that isn't an arbitrary complication invented to make growing the plant harder. There is usually a very good ecological reason for it.
Light, Darkness, And Other Germination Surprises
One of the easiest mistakes to make with seeds is assuming that all seeds should be treated alike.
We are often told to cover seeds with soil, for example. That is generally sensible, but some seeds germinate better when they are exposed to light. Very small seeds are particularly likely to be sown on the surface or only very lightly covered. If they are buried deeply, the seedling may simply run out of stored energy before it reaches the surface. Other seeds require light in order to germinate well.
I have had seeds germinate in unexpected places because of this. Nerine seeds, for example, started germinating for me while sitting on a windowsill rather than being buried in soil. Once I saw the little roots emerging, I planted them carefully, trying not to bury them deeply. That worked for me, although I would still check the requirements of the particular species rather than assuming every nerine seed will behave identically.
There are other surprises too. Some seeds respond to alternating temperatures rather than a constant temperature. Some need particular seasonal changes. Some have chemical inhibitors that need to be leached away. Others, such as many orchids, have rather complicated relationships with fungi or other organisms.
This is why growing unusual plants from seed is so interesting. Every now and then you encounter a plant that seems to have read a completely different set of instructions.
Temperature: Too Hot, Too Cold, or Just Right?
Temperature is probably one of the most common reasons seeds fail to germinate.
A packet of seeds might say that the seed germinates in spring, but spring is not a particular temperature. One person's spring might be another person's winter.
This matters particularly in Australia, where growing conditions can be very different from the climate in which a seed was originally selected. Seeds have a preferred temperature range for germination. Too cold and the seed may rot before it starts to germinate. Too hot and the seed can be damaged, dry out, or simply sit dormant until conditions improve.
I have planted the same seed more than once because the first sowing did nothing, only to discover that the second sowing germinated quickly when temperatures changed.
Cape gooseberry gave me one example of this. I planted some seed and it all failed to germinate, with the seeds eventually rotting. I replanted seed from the same packet a few weeks later, and this time almost every seed germinated. It is very tempting to conclude that the first batch was bad and the second batch was good. But both batches were from the same packet, while the temperature had changed quite significantly.
That is why I find keeping notes useful. Without records, it is very easy to remember only the successful result and forget all the failed experiments that came before it.
Don't Drown Your Seeds
Seeds need water, but more water isn't necessarily better. This is one of the simplest germination problems to fix.
The seed needs enough moisture for the germination process to begin, but it also needs oxygen. If the growing medium is permanently saturated, there may not be enough oxygen around the seed, and there is also a greater risk of fungal and bacterial problems.
This is particularly easy to do with small pots and seed trays. A little pot of seed-raising mix can stay wet for a surprisingly long time. I prefer moist rather than soggy conditions.
The same applies to cold wet stratification. When I put seeds onto damp paper towel in the refrigerator, I want the paper wet enough to keep the seeds moist while not sitting in a puddle.
There is a temptation, when a seed has not germinated, to water it again. Sometimes the seed needs more water. Sometimes it needs patience. Knowing which one is required is the difficult part.
How Long Should You Wait?
This is probably the hardest question to answer. The answer is: it depends on the plant.
Some seeds germinate in a few days. Others take weeks. Some take months. A few can take considerably longer. This can make growing from seed feel like a test of patience.
I have had seeds germinate while I was waiting for them, seeds germinate in the refrigerator, seeds germinate after I had moved on to other plants, and seeds germinate after spending a very long time apparently doing absolutely nothing.
Black raspberry is a good example. Even after the required cold, wet stratification, some seeds germinated quickly while others took months.
Muscari grape hyacinth was stranger still. Most people plat bulbs, but I wanted to grow them from seed. It seems they may need cold in order to germinate, and warmth seems to prevent germination. I cold wet stratified the seeds, and found that some germinated in the refrigerator. Seeds that had spent months in the fridge but had not germinated and were then planted outside did not behave in the same way. Eventually the only muscari seeds that germinated for me did so while still in the refrigerator in a zip lock bag. I don't pretend to have completely understood why.
That is an important part of writing about gardening honestly. Sometimes you can observe what happened without knowing exactly why it happened.
When Old Seed Isn't Actually Bad Seed
Seed age matters, but an old packet of seed is not automatically worthless.
How long seed remains viable depends on the species and how the seed has been stored. Some seeds remain viable for many years under good storage conditions. Others lose viability relatively quickly.
Over the years I have had the privilege of trying to rescue old varieties that were almost impossible to replace. One example was some old tomato seeds I saved when I was in high school from my first plant breeding project. I only had a few seeds, and they had been sitting in the back of a cupboard for well over 15 years. With so few seeds available, and their high sentimental value, every one mattered. Rather than assume the seed was all dead, I gave it a chance. Most of the seeds did nothing, but some germinated and grew.
That experience reinforced something I already suspected: old seed deserves to be tested before it is thrown away.
Of course, very old seed may have poor germination. It may also have none at all. But if the variety is rare or you have a packet you particularly want to preserve, it can be worth trying a few seeds rather than assuming they are useless.
The opposite is also true. Fresh seed isn't automatically perfect. Poor storage, immature seed, moisture damage, or unsuitable conditions can all cause problems. Some plants, such as when using true potato seeds, seem to germinate better for me after they have been stored for a year.
What To Do When Nothing Germinates
When an entire batch fails, I try to resist immediately blaming the seed. Instead, I work through the possibilities.
Was the seed viable? Was it sown at the right time? Was the temperature suitable? Was it kept moist? Was it too wet? Was it buried too deeply? Does the species need light? Does it require darkness? Does it have a hard seed coat? Does it need scarification? Does it need hot water treatment? Does it need cold stratification? Does it respond to smoke? Does it have another form of dormancy? How long should it normally take?
The seed packet should be the first place to look, followed by searching for reliable information about the particular species. If the conditions were wrong, I try again at a better time. If the seed has a dormancy requirement, I provide the appropriate treatment. If I am unsure, I often sow a small batch in more than one way. That isn't a particularly scientific experiment, but it can be useful. If one group germinates and the other doesn't, I have learned something.
Keeping notes makes this much more useful. Write down when you sowed the seed, what temperature it was exposed to, how you treated it and when germination occurred. It is surprising how useful these simple records become after you have grown the same plant a few times.
The Seed's Perspective: Germination Is About Timing
I think one of the most useful things you can learn from growing unusual plants from seed is that germination is not really about making a seed grow. It is about giving the seed the conditions it is waiting for.
A seed has evolved to germinate at a particular point in the plant's natural cycle. For some plants that might mean warm, moist spring soil. For others it might mean a period of winter followed by warmth. For some Australian plants it may mean smoke from a bushfire followed by rain.
Once you start thinking about germination this way, a stubborn seed becomes less frustrating. It isn't necessarily refusing to grow. It may be waiting.
Sometimes the solution is as simple as changing the temperature, reducing the amount of water, or sowing the seed at the correct depth. Sometimes it means giving the seed a period of cold, weakening a hard seed coat, or providing another treatment. And sometimes the correct response is simply to wait a little longer.
The most important thing is to find out what the particular seed needs before trying to force it into germination. Treatments such as stratification, scarification, hot water, or smoke are useful tools, but they are not general purpose solutions. Most seeds do not need special treatment, and unnecessary treatment can do more harm than good.
Seeds are remarkably good at waiting for the right conditions. After growing them for many years, I have learned to be a little more patient. If nothing has appeared in the pot yet, I don't necessarily assume that nothing is happening. Sometimes the most interesting seedling in the garden is the one you had almost given up on.
Article by Damien Beaumont
