Can you test seed germination viability by floating the seed in water? How reliable is this method and does it work for all seeds? If done incorrectly, germinating cannabis seeds can be a struggle. Luckily, we're here to help! Check out 5 germination mistakes you need to avoid! Are These Cannabis Seeds Good? Growing with bad marijuana seeds is particularly harsh on growers of all levels. This is mostly because it’s tough to pinpoint when the seed itself is the actual
Floating Seeds in Water – Is This a Good Seed Viability Test?
How do you know if your seeds are still viable? Simple, do a seed germination test. Place the seeds in some water. The ones that sink are still viable – the ones that float are dead.
This advice is all over the internet so it must work? But how reliable is it?
Floating Seeds in Water – Is this a Good Seed Viability Test?; source: Pens & Pencils
Do the Floating Seed Test Properly
If you check out a number of sites that describe this test you soon realize that there are several different ways to do it. Some people add soap to the water to reduce it’s surface tension. Others put the seed in a jar and give it a good shake or they might soak the seed for 24 hours before doing the test.
There is no agreement on how to do the test properly. That means the test results reported on social media are not very reliable since they rarely include the details of the method used.
There are also silly claims like “this method is not 100% accurate and it only works with freshly harvested seeds of certain fruits such as melon, watermelon, cucumber, squash, peppers and tomatoes”. There are thousands of different types of seeds. Why would it only work on some vegetables and what does “not 100% reliable” mean? Maybe it only works 10% of the time?
Another site says, “the test only works for melons or cucumbers if the seeds are fresh and have not dried out.” So it doesn’t work on purchased seed. This same site went on to state that you need to ferment tomato seeds to get them to germinate, and I have already shown that this is a myth.
This gardening technique is so poorly defined that it is not possible to know how to do it correctly.
Citizen Scientists – Floating Seed Test for Viability
A number of gardeners have done tests to see how well the floating seed test works.
Pulsatilla albana ssp. armena – the Pulsatilla ‘seeds’ are actually fruits – achenes with “fluffy tails”, source: BotanyCA
I had some red pepper seeds from a store bought fruit and tried floating the seeds without drying them. Half floated and half sank. I removed the floaters and used them to try the test again. Half floated and half sank. I then tested this last group of seeds for germination. The ones that floated and then sank had 8/10 germinate, and the ones that floated twice had 3/10 germinate. So it is possible that floaters have a lower germination rate, but the floaters in this test were certainly not all dead.
I tested some Camassia seeds; 38 of 48 (79%) sinkers germinated and 12 of 16 (75%) floaters germinated, after a month in the fridge using the baggy method.
Someone from our Garden Fundamental Facebook Group tested Briza maxima (quaking grass) and found better germination with floaters.
Marijuana seed that floats will germinate on top of the water in 24 hours.
Twelve different kinds of pepper seeds were tested in this video and both floaters and sinkers had good germination.
I’ve germinated quite a few clematis seeds and most of them have fussy tails. They all float. Many seeds have this characteristic including some grasses and pulsatilla.
Both floating and sinking peppers seeds germinate, source: Daisy Dawes
The top picture in this post shows two jars. The one on the left contains black pepper seeds – they sink. You can distinguish them from papaya seeds that float, and are frequently added to spices since they look like black pepper but are much cheaper.
Science on Seed Viability Using the Water Float Test
Acorns have very low germination because many seeds don’t develop completely inside the nut and because various pests lay their egg in viable seeds which are subsequently eaten by the larvae. Floating them is a common way to eliminate many of the non-viable seeds. Even with this test, too much agitation of the water will cause viable seed to float.
Juniperus polycarpos, the Persian juniper, also produces a low number of viable seeds. Floating in water is not a reliable means of separating the good from the bad, but floating in a sugar solution does work. Sugar water has a higher density than water and this difference can be used separate seeds of various densities. The heavier viable seed sinks.
The float test “works well with hard-seeded peas in the family Fabaceae (e.g. Daviesia, Chorizema, Gastrolobium and Gompholobium) and Mimosaceae (e.g. Acacia), and has also been used on species in Hemigenia with good success. Do not attempt this test on seed of Allocasuarina. Allocasuarina seed is mucilaginous. This means it has a mucous membrane around the seed that gets very sticky on wetting.”
Arabidopsis seed forms a sticky mucilage on the outside of the seed as it absorbs water. Mutations of arabidopsis have been found that don’t produce this coating, allowing them to be separated from normal types with a float test. This is an example where within a single species, some seed floats and some does not, depending on genetics that has nothing to do with seed viability.
Arabidopsis wild seed (WT) sinks while a mutation (mum) floats. The floaters germinate in 24 hours siting on the water, source Helen M North
“Wheat was used in one set of experiments, and the average of all tests showed a germination of 68.3 per cent for the sunken seeds and 72 per cent for those that floated. In another set of experiments lentil was used, and it was found that 75.4 per cent of the sunken seeds and 86.7 per cent of those that floated germinated.”
The floating characteristic of seeds depends very much on their weight, surface coating, shape and specific gravity. Some seeds do develop a large seed coat which can be empty and these likely float. The specific gravity of a seed is controlled by the environment (moisture) and internal enzymes and hormones. Some dead seeds sink, while some spongy seeds like spinach float even if viable.
Does The Seed Float Test Work for Testing Viability?
There are cases where a float test can be used to identify viable seed, but when science reports on these they are quite specific about the type of seed and the method used.
On the other hand gardeners tend to simply lump all seeds into one category and say they all work, without specifying the method that works.
As a general rule, gardeners should assume that the float test does NOT work for testing seed viability, unless there is evidence it works in a specific case.
A Better Way to Test Seed Viability
Use my baggy method if you want to test seed germination. You will actually see the root come out of the seed and know for certain that the seed is viable.
Top 5 Germination Mistakes To Avoid When Growing Weed
Germinating cannabis seeds is necessary in order to sprout seedlings that develop into mature, healthy cannabis plants. However, complications with light, humidity, heat, and more could result in cannabis seeds failing to sprout. Find out what to avoid to ensure successful germination.
Germination is where the magic begins. Cannabis seeds must first germinate in order to sprout and begin their journey as living, breathing plants. However, if the germination process is done incorrectly, or is thwarted by some other variable, seeds can fail to sprout, leaving you with useless, spent seeds instead. Here are the top five mistakes to avoid when germinating cannabis seeds.
GERMINATING BAD SEEDS
One of the most common reasons seeds fail to germinate is because they are simply duds. Typically, healthy cannabis seeds should look a specific way and be of a specific colour. Viable seeds will appear round, not flat, and should be a beige to dark brown colour with subtle tiger striping. Seeds that have been flattened or are pale in colour may have a tough time sprouting into healthy cannabis plants.
Seeds that have been improperly stored may also fail to germinate. These tiny packages of DNA prefer to be kept in a cool, dark place with moderate humidity. Exposing them to heat, light, or extreme humidity levels (both high and low) could result in seeds losing their viability. As long as you source your seeds from reputable seedbanks and store them appropriately, you shouldn’t have to worry about bad seeds ruining your chances of successful germination.
TOO MUCH LIGHT
Generally speaking, seeds require a dark environment in order to germinate. After all, in nature cannabis seeds find their home in the dark embrace of soil. It can be hard to determine exactly how much light is too much for your seeds; however, err on the side of caution and germinate out of direct light. There’s no need to use your grow lights until after germination has occurred.
It is also likely that the quality of your seeds will affect their ability to handle direct light. Seeds that are already having a tough time germinating will have an even worse time doing so if they are exposed to excess light.
TOO MUCH OR NOT ENOUGH WATER
The amount of water you supply your seeds during the germination process will also affect their ability to successfully germinate. Some growers attempt to germinate by “drowning” them in a glass of water. While this ensures they will not go thirsty, it can actually be more harmful than helpful.
Once they pop, seedlings are very delicate and must be watered carefully. When germinating, your medium should be damp, but not overly wet for best results. On the other hand, a dry environment is basically a death sentence for your seeds. They need a constant source of moisture to sprout, otherwise they’re good as duds.
Cannabis seeds require a specific temperature range in order to germinate. Regardless of the germination medium you are using (soil, paper towels, etc.), the temperature in the environment should consistently sit in the 26–28℃ range. Seeds need to be kept warm during the germination process. At no point during germination should seeds be exposed to temperatures below 20℃.
There are some techniques that can be used to ensure your seedlings remain in this temperature range. Some growers choose to use special warming mats that can be set to a specific temperature and placed underneath the seedling containers. Another strategy is to place a timed heater close to your seedlings to warm them up occasionally. Once your seeds have sprouted, they will be much more resilient to fluctuations in temperature.
GERMINATING IN SOIL
Many people choose to germinate their seeds using paper towels. However, others choose to do so directly in soil. Of course, germinating your seeds in soil isn’t inherently bad, but it can come with its own set of challenges, and is generally not recommended unless necessary.
For instance, the upper layer of soil can dry out within 48 hours, making it more difficult to give your seeds the right amount of water they need without overdoing it. Giving your soil too much water during germination could result in the seed rising up or dropping down further, inhibiting its viability. Moreover, seeds that are planted too deep in the soil could experience a host of complications. They could suffocate before coming into contact with enough oxygen, and be unable to access sufficient light to progress into the seedling stage of their life cycle.
Seeds may also be unable to germinate if the soil they are planted in contains contaminants. Mould and pests can easily kill a mature, healthy weed plant within just a matter of weeks. It should come as no surprise then that they could also prevent a small seed from germinating. If your soil contains traces of these contaminants, it is possible that your seed will never actually open and sprout. This also applies to fertilisers. Even small amounts of fertiliser in your soil can effectively kill your seed, making it completely useless.
Are These Cannabis Seeds Good?
Growing with bad marijuana seeds is particularly harsh on growers of all levels.
This is mostly because it’s tough to pinpoint when the seed itself is the actual problem. Most growers will blame themselves for a problem that shows up in their grow long before they assume it’s the seeds.
The term ‘bad seeds’ usually refers to any type of seed that has a significantly higher likelihood of causing problems in a grow. I’ll cover the most common reasons for bad seeds in this tutorial!
These cannabis seeds were germinated between two wet pieces of paper towel!
These are pot seeds you might get from a friend, or maybe you have them stashed somewhere and forgot how you got them. In either case, if the shell of the seed looks beat-up, it may not germinate as well or quickly as seeds that were stored in good conditions.
Seeds are a little nugget of genetic material than can hopefully grow into a plant. And like all other genetic material, it doesn’t last forever! Although seeds can be viable for quite years and years after they’re first produced, the chances of them successfully germinating goes down over time (and old seeds also tend to take a lot longer to germinate than fresh ones). The resulting seedlings are also more likely to be slow growing. But sometimes they sprout like they were born yesterday!
Check out the picture below. We sprouted all the plants at the same time. The tub on the right has seeds that were planted within a week of receiving them in the mail. The tub on the left has a very popular strain with award-winning genetics… but the seeds were more than 6 years old from when we first bought them. Even though they were all put into the tank at the same time and the new seeds grew like crazy, the seeds on the left got outpaced by algae – only one sprouted and though its roots keep growing and growing the actual never got any bigger than two round leaves even after a month!
Pale or Flimsy Seeds
When I first started growing I was told that good cannabis seeds needed to be very hard with dark tiger striping. If you could crush it between your fingers, it was a bad seed, or so I was told. This has not been my experience at all!
Did you know that the “stripes” on cannabis seeds are actually part of a protective coating? The “pale” seeds in this photo are actually just regular seeds with the coating rubbed off!
Over the years, some of my very best plants came from flimsy, light brown seeds that very likely would have been easy to crush between my fingers.
So I’m a big believer in the fact that if you put the seed in the ground and a fast-growing healthy seedling comes out of it, it was a viable seed! Don’t toss a seed you are really interested in just because it’s a little pale; give it a chance (I’m talking more about tan seeds, it’s very unlikely a yellow seed will sprout)!
Note: Although the hardiness of the seed was likely important in the wild, cannabis growers have been breeding plants for generations to make good buds, not seeds! We growers strive to provide an ideal germination environment that lets almost any seed germinate successfully. As a result, we haven’t been breeding for seed hardness. Just like a teacup poodle hasn’t been bred to be strong, cannabis seeds haven’t been bred to be strong. They have other qualities we love
Bag seeds you randomly find in your buds aren’t supposed to be there, so that means that the genetics are a toss-up. Even if the seeds started with good parents, there’s no telling how high or low the quality will be. Unfortunately, the only way to find out is to grow it… Some growers win the genetic lottery, but many others lose out.
If you talk to breeders, you’ll learn that when you breed two “star” strains together you don’t always get what you’d expect. It seems like every one of the seedlings (or at least most of them) should be capture the best qualities of both their parents.
However, that’s not how genetics works most of the time. Without intensive breeding and backcrossing, when you mix two random plants you often end up with only a fraction of the seedlings capturing the best of both parents.
Bag seeds are a wildcard! You never know what you’ll end up with!
So depending on how the seed was originally made, bagseed often has a lot of variety. Even if the buds you got were an incredible quality, it doesn’t necessarily mean that the seeds will produce buds like that. If you’ve ever gotten involved with breeding or growing other types of specialized plants like roses, hops or even apples, you’ll know that seeds rarely breed “true” to the parents, and cannabis isn’t any different.
That being said, sometimes bagseed is all you have, and lots of growers get lucky!
Hermaphrodite or Male Plants
If a cannabis seed was produced with a male doing the pollinating, it means that about half of the resulting seeds will end up being male (which you don’t want, because only female flowers turn into bud). In that case, you want to determine the gender of your young plants as soon as you can so you can toss all the male ones before they start making pollen sacs.
If growing with seeds that were produced without a male plant around, the seeds sometimes end up being hermaphrodites, which means they grow both male pollen sacs and female flowers (again, something you don’t want).
One of the best ways to ensure all your plants end up being female is to start with feminized cannabis seeds from a trustworthy breeder.
Sometimes It’s Random!
Even if you’re starting with the best, most fresh seed stock, occasionally you’ll get an individual seed or plant that just doesn’t grow as well or quickly as the others, or maybe you’ll get a super awesome seedlings that just starts kicking butts and taking names from its first moment.
Natural variation is totally normal! It’s always a good idea to sprout at least a few more seeds than you need in case you happen to run into a runt, or some other expected problem! If all your plants are healthy and growing fast except one, you can blame the seed!