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.
Can you germinate weed seeds in a glass of water?
Cannabis Germination Technique via Soaking in Water A common germination method for cannabis is to soak the seed overnight in a glass of water that is at room temperature because this triggers hormones that signal the cells to start germinating.
How long it takes for weed seeds to germinate?
Some seeds germinate very rapidly while others can take a while, but generally, seeds should germinate in 3-10 days. If it’s been two weeks and a seed hasn’t sprouted, it’s probably a dud and won’t sprout. A seed has germinated once the seed splits and a single sprout appears.
What does it mean when a weed seed sinks in water?
Since viable cannabis seeds float on the surface of the water, they are able to retain the proper ratio of moisture and air. Seeds that do not float may be sterile or underdeveloped. Immature cannabis seeds appear green or sometimes white and as stated above they will sink to the bottom when you attempt to float them.
Can you germinate seeds in just water?
Why would seeds not germinate in water alone? Plain water usually doesn’t have enough of the nutrients needed for seeds to germinate. Also, there is nothing in the water for the roots to grasp onto as they develop.
Can you drown weed seeds?
The goal is to keep the soil in the Jiffy moist during the germination process, but never drowned. Some growers water the Jiffy too much, and more often than necessary, and end up drowning the seed because excessive moisture prevents the ventilation of the seed, stopping its germination.
Why are my weed seeds not germinating?
If you reuse soil and it is not sterilized, there is a high chance of mold and other unhealthy organisms like insects and bacteria. As a result, the seeds may not sprout at all. Even if they grow, these organisms might kill them after a couple of days.
How do you plant weed seeds after germination?
Place your germinated seed, root down, into the hole and cover lightly. Do not pack the soil on top of the seed; a light protective layer of soil is all that is needed. Once they sprout in one to three days, new seedlings will need lots of light, and fluorescent grow light works best.
Should I soak my seeds in water before planting?
It is recommended that you only soak most seeds for 12 to 24 hours and no more than 48 hours. After soaking your seeds, they can be planted as directed. The benefit of soaking seeds before planting is that your germination time will be reduced, which means you can have happy, growing plants faster.
Do female seeds float or sink?
One method to check for seed viability is the water test. Take the seeds and place them in a container of water. Let the seeds sit for 15 minutes. If the seeds sink, they are still viable; if they float, discard, because they probably will not sprout.
Why did my weed seedling fall over?
Abnormal stretching in the seedling phase is a sign of stress. By far, the most common situation that causes seedlings to stretch and topple over is light deprivation. In the same way taproots dig for water and nutrients, the top part of the plant will stretch vigorously if it’s not receiving enough light.
How to Germinate a Cannabis Sativa Seed
The following is a successful step-by-step process for germinating cannabis seeds on any budget. Germination of marijuana seeds, cannabis sativa, & pot seeds with minimum failure.
Always be sure that your work area is clean. This includes YOU. Wash your hands every time before working with seeds – it will increase your success.
Germinating Marijuana Seeds
Preparation & Supplies
In preparing to germinate your cannabis seeds whether one or a dozen, make sure you have everything you need and that it is also CLEAN. I use anti-bacterial soap in my garden for myself mostly, I recommend using it for everything (hands, buckets, tweezers, shot Indoores, etc.).
(shot Indoor method)
For our tutorial, we are using a shot Indoor, mineral water at room temperature, and our chosen seed(s). We use masking tape and a black marker to identify our seeds when germinating multiple cannabis strains.
You can use your local water with one caution. Fill a pitcher with your water 24 hours before using it & leave it open. This allows chlorine and other potentially harmful chemicals to escape into the open air.
Cannabis Seed Germination
Half fill your Indoor with mineral water. We have taken a single seed (female), and placed it in the water (shot Indoor). Notice that the seed is initially floating.
We have identified this seed and now we need to put it away in a warm and dark place for 24-30 hours. This allows the seed to absorb water. The seed does not need or like any light yet, but likes everything warm.
The cannabis seed simply needs warm air, moisture and darkness to begin a good germination process.
Keeping a temperature of between 75 to 85 degrees Fahrenheit is excellent for starting seeds. Warm, wet and dark is what they like.
Select a warm spot that stays consistent in the temperature it offers (like on your water heater). We cover our Indoor with a dark cup to keep out all of the surrounding light.
Again, leave this covered and warm for at least 24 hours. This will allow the seed to absorb water, and is an excellent indication that the seed can grow.
The cannabis seed sinks when it absorbs water (24 hours). When you return the next day and uncover your Indoor, you may notice that the seed sank to the bottom.
If it did not, have no fear. Try stirring the water with your clean finger. The seed may have absorbed water and still be afloat by a bubble or dry spot (happens all the time).
How to Germinate
If the seed still floats, you can add some fresh water* and check back again in 8-12 hours. After that, you can still plant the seed, but chances are slimmer that it will take hold (germinate).
I then take a cup of my personal grow mix (soil) that is the same mix I use in my plants through-out their maturity.
I only transplant once, and it’s moved into the same exact grow medium in it’s final container. This prevents additional shock or stress when transplanted.
Each time you change containers or transplant, it will make the plant stress for a week or so.
Use a humidity dome until the seeds break ground (already germinated).
I use a solo cup and slice four slits in the bottom for good water drainage and added aeration. It also makes the transplant very easy.
I carefully place the seed into the soil with the knot side up. I only place it about 3/16″ under the soil surface and water thoroughly. I am still only using water* at this point.
When I water* the soil, it tends to move some soil over the seed. I label my cup and place it in a dome for high humidity and added warmth (shown next to a clone). Position a small grow light above the dome and have the timer the same as your 18 hour garden clock. We want some air, moisture, warmth and light right now.
Lights should remain ON for 16 – 20 hours and OFF for 4 – 8 hours. You are deciding this right now, because changing this light cycle in mid-growth IS stress for the plant – we will control the lights completely. This is the ‘trigger’ for future growth stages. I recommend 18 hours ON, 6 hours OFF once germinated.
Keep the soil moist, but not wet. there is a difference. After my initial watering, I do not water* it again for 2-3 days, and then I am spraying water* over my cup of soil.
Usually, in about 2-5 days you will see the seedling begin to pop out of the soil. I have seen seeds take 11 days, but usually less.
Sometimes, as in this example, the seed shell stays attached while the seedling works it’s way upward and fights to exist.
Cannabis seed curling upward with seed shell still intact.
Spray the leaves with water* for two days to help transition from the high humidity dome. Don’t water yet, just spray them.
Germinating marijuana seeds
Once the seedling has broken ground and I can see green leaves, I remove the cup from the humidity dome. Move your new baby to the nursery side of your garden with the 16-18 hour grow light cycle and circulating air.
As the seed uncurls and begins it’s beautiful life, it will lose the seed case and begin to sprout it’s first leaves.
As you can see, the sprout stretches upward while wrestling with the seed casing to be released (all this work for our smoking pleasure).
As it spends more time under the light, the sprout should be able to shake the seed and begin to form it’s first 2 leaves (cotyledon).You will find that once you have a regiment down that works, it’s fairly easy to germinate your cannabis seeds indoors at any time of the year.
Congratulations! We have now moved from the germination stage to the seedling stage. Patience, cleanliness and good soil products can help insure a high percentage of germination success with your marijuana seeds.
Germinated Cannabis Seed
First Week (Seedling)
Your new seedling is alive and prospering. In our example, you can leave it in the cup for a couple of weeks while it gains strength. It has everything it needs to begin a stress free life. From here we move into the caring and growing of your marijuana.
At times, I plant more than one seed to a cup. Sometimes I leave them both in the cup, and sometimes I separate them immediately after they break ground.
You should now be on your way to some wonderful romance with your plants.
Do not be afraid to “talk to” and raise your youngsters to be strong, vigorous and ‘stinky’ young ladies.
Be careful not to over water* your seedlings. Wait for the top of the soil to get dry and crusty before you consider watering again.
Water* – In this Chapter, the term water relates to mineral water, distilled or bottled water, or house water that has sat in open air for 20-30 hours.
Giving the seedlings a mild nitrogen mixture in your water* will help vigorous, healthy growth at this stage (if your soil does not compensate in this important area). Be careful! They are still young and very impressionable.
Once your seedling has 5-7 growing days in the cup, you can transplant it anytime to it’s larger container. Make this large enough for the life of the plant (I use 5 gallon containers) I never want to run out of room (soil) at the point of flowering.
I recommend water* throughout this process because my soil mixture contains initial nutrients like nitrogen, phosphates, guano, seafood, and more. At some point, you’ll probably develop your own soil too.