Cannabis Seed Germination Rate

How to Improve Germination Rates with a Reptile Heat Mat Some cannabis seeds can’t be replaced. You may have a strain or cross that’s no longer available. In the past, I’ve tried to order Whether you are a cannabis fan who has just begun growing a couple of plants recreationally, or you are looking to test your green thumb for the first time, there is one question that’s going to come up at some point. Do seeds go bad? Let's find out! Why Are Your Cannabis Seeds Not Germinating? Many first-time growers and inexperienced planters often experience this problem when trying to cultivate cannabis seed. They end up languishing and

How to Improve Germination Rates with a Reptile Heat Mat

Some cannabis seeds can’t be replaced. You may have a strain or cross that’s no longer available. In the past, I’ve tried to order cannabis seeds again, only to find the breeder disappeared. Sometimes germination problems cause irreplaceable losses. On top of that, cannabis seeds can get expensive, especially small-batch seeds or experimental seed crosses, which means if seeds don’t sprout you are down significant cash.

So far I’ve had 100% germination using this method (including several seeds that were 2 years old). Learn how to do this yourself in today’s germination tutorial.

Germination problems are some of the most frustrating problems when growing cannabis. It seems like you should be able to stick a marijuana seed in some soil and let nature take care of germination. Why is it so hard to germinate seeds? What can a beginner or experienced grower do to improve germination rates? Bonus: Why are some seeds harder to germinate than others?

What cannabis seeds want during germination:

  • Moisture – never let seeds dry out after they get wet, but also don’t let seeds sit in liquid water or seedlings may “drown” after they crack open the seed
  • Warm – 80°F (26°C) is perfect, though any temperature between 75-85°F (24-30°C) is good
  • Dark – too much light can hurt germination so it’s recommended to germinate seeds in the dark
  • No touching – try not to touch or move seeds after they start germinating until they sprout
  • Clean – bacteria and microscopic fungi can slow or stop germination so make sure to wash your hands before handling seeds and germinate seeds in a clean place

So what’s the best way to give this perfect germination environment? Today I want to share the cannabis germination method I use. I’ve found most germination methods work, but one of the key things that seem to help germination go faster (and reduce the number of seeds that don’t germinate) is warmth. Seeds want it to be warm but not hot, like they’re just under the surface of the soil on a sunny spring day after a light rain.

Seeds want to “feel” like they’re just under the surface in moist dirt on a warm day. Your job is to give them a better version of nature.

Over the years I’ve struggled to achieve the perfect germination temperature. In my experience, “seedling heat mats” don’t keep a consistent temperature, and they often get too hot after a few days. I’ve germinated seeds on a seedling heat mat and I’m pretty sure they got cooked, which caused them to take much longer to germinate. So how can you achieve the perfect 80°F / 26°C temperature that seeds love? Reptile heat mat!

Why a reptile heat mat?

When you keep a cold-blooded animal like a reptile as a pet, you need to provide heat to keep them warm. However, you want to make sure their home is always the perfect temperature. If it gets too cold or hot, they can die. It’s up to you as the owner to make sure they get just-the-right temperature so they’re happy and healthy.

Pet snakes and other reptiles can’t control their own temperature so they need you to provide just the right amount of warmth

That’s why reptile heat mats were first created. It’s essentially a seedling heat mat, except it has a probe with a sensor to allow you to choose the exact temperature that you want. For example, you can set the heat mat to keep the temperature a steady 80°F / 26°C and the controller will turn the heat mat on and off so it stays exactly that temperature day and night. I’ve found that using one of these mats causes seeds to germinate much faster than if they weren’t heated, but (unlike with regular seedling heat mats) the sensor prevents the mat from ever getting too hot and cooking the seeds.

This reptile heat mat took my marijuana seed germination rates from 90-95% to almost 100% germination every time.

A reptile heat mat comes with a temperature controller to automatically let you keep your seeds at the perfect temperature so seeds germinate as quickly as possible (with no chance of overheating like with a typical seedling heat mat).

What you need

  • Reptile heat mat – they come in different sizes (bigger ones can produce more heat), but the 6″x8″ size mat (uses 8 watts) should be more than enough to germinate a few seeds
  • Paper towels – the cheaper the better (cheap rough paper towels work better for germinating seeds than the more expensive or cloth-like paper towels)
  • Kitchen plates – you’ll use these to lock in moisture and keep seeds in the dark during germination
  • Seeds – Here’s where to find seeds
  • Seedling plugs (optional) – Seedling plugs like Rapid Rooters are a great place to put your newly sprouted seeds before planting them in their final home. Or just put germinated seeds directly into the soil.

Wet paper towel method – germinate seeds between wet paper towels

Use another plate on top to lock in moisture and then set up the heat mat underneath to maintain the perfect temperature (full germination tutorial below)

100% germination almost every time!


1.) Choose seeds

When starting with feminized seeds (which means all plants will be female and make buds) I germinate at least one extra seed per strain just in case a seed doesn’t germinate. If I’m sprouting non-feminized (“regular”) seeds, I germinate 4-5 seeds per strain to ensure there’s at least one female plant. Even though about half the plants from regular seeds should be female, sometimes you get unlucky and get a lot of male plants (which don’t make buds). If you don’t want to worry about male or female plants, I recommend sticking to feminized seeds so every plant ends up being female.

2.) Set up paper towels and plates

Cut your paper towels to fit your plates (if any paper towel is sticking out, it will dry everything out) and label them with the names of seeds.

Prepare paper towels, plates, and label with your chosen strains

2.) Set up reptile heating mat

In order to get everything working properly, you need to find a way to get the probe near the seeds, but not in with them or it will let light in. I’ve found the best way to do this is to place down the mat, and use a third plate upside down so you have a great place to put the probe, then set your germinating seeds in their plate on top. So you will have 3 plates in total. One to attach the probe to, and two more to encase your seeds.

Set down heating matt, and attach probe to plate.

Set the plate down. At this point, the probe is just above the heating mat. Perfect!

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Add your prepared plate on top. Now it’s got the heating mat underneath, yet still an extra layer of protection to cause all the heat to radiate equally

3.) Place seeds next to their labels

Be careful not to let them roll around or you may lose track of which is which

Add seeds to their proper place. Be extra careful not to let them roll around or you won’t know which one is which after they’ve germinated. Here’s an example.

4.) Add water and cover

Gently add a little clean water, making sure to get the paper towels wet without accidentally moving the seeds around. Then take a single sheet of paper towel and add it on top. It should quickly become wet too. You want everything to seem wet, but there shouldn’t be extra water sloshing around. It shouldn’t appear too shiny. If there is visible water (for example you see water moving if you gently tip the plate), carefully dab it off with another paper towel. You want your environment totally moist but still solid.

Add water (gently without letting seeds roll around) then put a single extra sheet of paper towel on top. If you only use a single sheet of paper on top, you will still be able to see what’s underneath pretty well, as pictured here. This lets you see when seeds are germinated without disturbing them.

Having just one sheet of paper will ensure seeds get air and let you see whether they’ve germinated without having to disturb them. Seal the moisture in with another plate. Make sure no edges of the paper towels are sticking out around the edges or they will slowly wick out all the water and possibly dry out your seeds.

Seal the moisture in with another plate. Make sure no paper towels stick out the side or they’ll wick away moisture and dry everything out.

5.) Set the reptile heater to 83°F / 28°C

This isn’t an exact number (anything around 80-85° / 26-30°C does awesome), but it’s the temperature I choose. I figure a little heat is lost through the plate and it likely gets the seeds at a nice 80°F.

This is what the controller looks like

I set the reptile heater to 83°F / 28°C, but anything around that range works great. Here’s a quick video showing how to set the controller. Hold the “set” button until it blinks, set the temperature you want, then hit “set” again. You’re good to go!

If you check back in about an hour, the water should feel tepid or just slightly warm (it will never feel hot). If the water feels cold, then turn up the reptile heater a few degrees as you may be losing heat from your specific plate or your air is just a bit colder than mine.

Check on the seeds once after an hour and touch the paper towel in the middle to make sure it feels lukewarm (not hot or cold). If so, you’re good! Close it back up and try not to peak again for at least 24 hours. I know it’s hard not to check on them every hour (at least it is for me), but they will germinate better if they’re undisturbed in the dark.

6.) Seeds usually sprout in 1-3 days

Try not to check on them for 1-2 days except to make sure the temperature is right and no paper towel is sticking out the sides. Seeds like to be left alone during germination.

Before sprouting, this is what the seeds look like under the paper towel (little black dots). If you see this, cover them again and check back tomorrow.

Since you only used a single sheet of paper towel on top, you should be able to see if at least some of the seeds have germinated without having to disturb them. If you don’t see roots yet, just close the plate up and check once a day from now on. Some seeds, especially older ones (or certain strains) can take several days to germinate.

This is how seeds look once they have sprouted (through the single sheet of paper towel on top). You can faintly see their roots, and sometimes you can ever see yellow leaves. Note: the leaves are fully formed (but yellow) in the seed and break free during the germination process.

And here’s what the seedlings look like after gently peeling off the top layer

It’s normal if new seedlings look yellow (the leaves are always yellow inside the shell, but turn green once they get exposed to light)

7.) Put germinated seeds in their next home

At this point, you can put your seeds directly into their next home. I like to put seeds in Rapid Rooters because that gives me a few more days to examine all the seedlings and see which ones are growing the best before picking the winners for their final home.

You can also put germinated seeds directly into soil or coco, just be gentle and try to plant seeds with their roots down.

Put your sprouted seedling inside, with the seed head just under the surface

Gently close the Rapid Rooter around the seedling and put it in a tray or shot glass (or any way to hold it upright while the root is growing). If the seed/seedling seems loose like it might move around, pick a little piece off a Rapid Rooter and gently put it in the hole to make sure the seed head is totally secure (you don’t want it moving around while the root is still growing into the seedling plug).

Put Rapid Rooters under gentle light in a warm place (for example in your regular grow spot with the light 2-3x further than normal, or near a sunny window)

Soon your sprouts will be seedlings

Once seed leaves are about the width of the Rapid Rooter, they’re ready to be planted in their final home

Do Cannabis Seeds Go Bad?

M any pot fans are starting to look into growing their own supply. After all, how hard can it be? Nature does it all the time, and it doesn’t even have any grow light options other than the sun. While you may not be producing showroom quality nugs, there’s a pride that comes with tending to your own garden and snipping buds straight off the branch. Plus, you can’t beat the price.

Plenty of online stores sell seeds so it’s pretty easy to pick your favorite strains to start. However, if it’s been a while since your seeds arrived and they’re not yet planted, you can forgive yourself for wondering if maybe you’ve waited too long. After all, how long do marijuana seeds last? Whether you are a cannabis fan who has just begun growing a couple of plants recreationally, or you are looking to test your green thumb for the first time, there is one question that’s going to come up at some point.

Do Marijuana Seeds Go Bad?

First off, marijuana seeds are the same as many other plant’s seeds. A waxy outer shell called the seed coat protects the embryonic shoot, stem, and root contained within, which are nourished by a nutrient-rich oil surrounding them. As long as the shell remains intact and the plant inside doesn’t dry out or get damaged, your seed can still grow into a cannabis plant.

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However, this shell will not last forever. Once it dries out and hardens the seed coat can crack and expose the embryonic plant to damage. Or the seed coat hardens to the point that it no longer lets in moisture. In both cases, the seed is no longer viable.

Of course, there is some debate in the cannabis community over how long do marijuana seeds last. Some growers claim that when stored in the ideal conditions, marijuana seeds can last anywhere from six months to a year after packing and still spout once placed in the soil. Other producers believe that marijuana seeds can last up to a decade if properly refrigerated in the right containers.

Most seed producers agree that on average three to six years is a maximum for viability, and every day that the seed is stored drops the chances of it germinating just a little bit.

So how long do marijuana seeds last? In general, six months is the maximum if you’re looking for a nearly 100% germination rate. After three years, you’re looking at a germination rate of around 50%.

What constitutes “ideal conditions” for cannabis seed storage also depends on the genetics of that particular plant. Some cannabis strains produce a much hardier, longer-lasting marijuana seed that can last for years and still stretch their leaves once planted. Others produce seeds that need to quickly return to the soil.

How Marijuana Seeds Are Stored

In terms of long term storage for your marijuana seeds, there are four main factors to consider:

When it comes to how long marijuana seeds last, temperature is the main factor. In nature, heat tells the seed that winter’s over and it’s time to start sprouting. If your marijuana seed’s not in the soil, this means that the plant matter inside the marijuana seed will begin to germinate and then rot.

41 degrees Fahrenheit (5 degrees Celsius) is the absolute warmest you want your storage spot to be, with the sweet spot being somewhere around 38 degrees Fahrenheit.

If you are refrigerating your marijuana seeds, they’ll last the longest in a separate unit or a spot near the back. Every time you open your fridge you are changing the temperature which can harm the seeds over time.


Humidity is also your enemy when it comes to how long your marijuana seeds will last. When a seed gets wet, it cracks open to allow the sprout and root out. This will let in rot if the seed isn’t planted. A humidity level of about 5% is the maximum you want to allow.


Much like heat and humidity, light tells that seed to wake up because it’s time to spring forth.

In order to keep your seeds from going bad, it’s best to keep them stored in a dark container in order to avoid light. photo credit

By keeping your seeds in a dark or opaque container, they’ll keep dozing long term. Light can also damage the surface of the marijuana seed, which in turn will damage what’s stored underneath, causing your marijuana seed to go bad.

Besides being dark, for your marijuana seeds to last long term, you want to expose them to as little oxygen and carbon dioxide as possible. These gasses are what growing plants breathe, as well as the pests that consume them. If you’re refrigerating or freezing your marijuana seeds, make sure your container is as airtight as possible. If you can vacuum seal them, even better.

Alternatively, if you’re planning on planting in the next few months, regular mailing envelopes will do in a pinch. They’ll keep the marijuana seeds out of the light and dry, so all you have to do is store them in a cool place. Plus, envelopes make it easy to label your strains so that you can keep them separate.

How To Tell If Your Marijuana Seeds Are Still Healthy?

What should you do if you find some old seeds and have no idea how long they were stored? Maybe past you put them in a freezer bag in the hopes of keeping your favorite strain alive, or found a couple at the bottom of a baggie that the trimmer missed.

How do you know if your marijuana seed has gone bad, or if it’s healthy and viable to grow into a plant? There are four easy ways to check if your marijuana seed is still good.

Dark Color

If your seeds are dark brown, black, or gray, that’s a very good sign. The shell is intact and uncompromised, which means the genetic material inside has been kept safe.

Seeds should have a dark color. If seeds are still green they are probably not ready yet. photo credit

Viable seeds should also have stripes or spots all the way around. If the seeds are white or green, they’re most likely still immature.

Waxy Coating

Check if the seed still has a waxy coating. A healthy seed should have a slight sheen to it, as though it’s been oiled. This means the seed still can retain moisture.

Hard Shell

If the seed is still healthy, you should be able to lightly squeeze it without it crunching between your fingers. If the shell has no give and splits or splinters under light pressure, then your marijuana seed has gone bad and has no chance in the soil.

Cracks or Holes

If there are any cracks or holes anywhere on the shell, your marijuana seed’s likely gone bad and will most likely not sprout. Bacteria and other harmful lifeforms can find their way into the seed, or it will dry out.

The True Test of a Cannabis Seed

Of course, the best way to test whether your seeds will sprout is to plant them and see. If some green shoots climb their way out of the soil after a couple of days or weeks, you’ve got your answer.

Storing marijuana seeds is a great way to make sure you always have your favorite strains on hand, as well as to keep yourself stocked up on plants for the long haul. Luckily, marijuana seeds can last for years as long as you make sure your seeds are cool, dry, airtight, and out of sight. There’s no better time than now to learn a new skill, so let’s see how green your thumb can get.

How Do You Tell If a Seed is Good or Bad?

If the seed is dark with stripes or spots all the way around, has a waxy shell that doesn’t crack when you give it a light squeeze, and doesn’t have any visible cracks or holes, it’s probably still good. If there are holes in the shell, it’s dry, or especially pale, your marijuana seed’s probably gone bad.

Do Autoflower Seeds Go Bad?

All marijuana seeds can go bad, including autoflower seeds. However, by keeping your seeds at a stable 38 degrees Fahrenheit and at around 5% humidity, as well as airtight and out of the light, your seeds may last up to 5 years or more.

How do you like to store your seeds? Share your thoughts in the comments!


Paul Barach is a Seattle-based freelance writer, editor, and author with experience creating well-researched, edited web articles covering cannabis news, culture, history and science. Paul is a regular contributor to PotGuide and has also contributed to publications such as, SlabMechanix, Litro, and The Trek. He prefers to spend his free time outdoors and most recently hiked the Pacific Crest Trail. So far he has only fallen into the La Brea Tarpits once. You can follow him on Instagram @BarachOutdoors and stay up to date professionally through his LinkedIn page.

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Why Are Your Cannabis Seeds Not Germinating?

Many first-time growers and inexperienced planters often experience this problem when trying to cultivate cannabis seed. They end up languishing and wondering why their effort is not yielding since a cannabis seed has a pretty high germination rate (99%). However, many things might not promote the germination process.

Generally, cannabis seeds are powerful and grow pretty fast. If the seeds do not germinate, there is likely a problem with the germination method. This article will explore many things that can go wrong when trying to cultivate cannabis seeds.


The chances of having a viable seed increase significantly if the genetics is good. This is pretty important as it can avoid wasting energy and effort trying to germinate a bad seed. When you buy good quality seeds from trusted banks, you can breathe a sigh of relief, knowing that your actions will not be wasted.

As a result, it is not a good idea to grow seeds that you stumbled on inside a cannabis bag you got. Such seeds could be infertile and may not germinate. If it eventually germinates, you might not like cannabis. Make sure to buy the right seed from reputable stores and increase the chances of germination.

Direct Soil Germination

This is one of the top reasons your cannabis seed is not germinating. If you do not water the substrate before sowing the seeds and water afterward, there is a high probability that the seeds will not grow. This is not surprising as the seeds could be buried too deep, and adding water after sowing worsens this.

You can obtain good results by germinating the seeds in jiffy pellets, peat plugs, or using kitchen paper and later transplant them to a pot or the soil when the small seedlings come out. Make sure to care for your tender plant at this stage. Limit irrigation, support the right temperature and use Northern lights when growing indoors.

Wrong Temperature and Humidity

The ideal temperature for germinating cannabis seeds is high humidity and high-temperature levels. It is essential for people in tropical countries to provide external support of heat to get the temperature within reasonable and acceptable ranges. This is where heated greenhouses come in. Not only do they provide the right temperature, but they can get the humidity level to the ideal range essential for germinations. A cannabis seed needs 70% relative humidity and an average temperature of about 270C for germination.

If the temperature and relative humidity ranges are lower than the ideal value specified, the growth rate will be slow and unsuccessful. Excessive range, on the other hand, can lead to fungal problems.

Seeds Planted too Deep.

The amount of energy available to a germinating cannabis seed is limited. As a result, if planted too deep, it might not have the required energy to make its way up. A seed planted underground will have no light and is not producing food yet since no photosynthesis. Planting seed too deep creates extra stress for the seedling as migration to the surface becomes an issue.

As a result, you should plant your cannabis seed around 2 to 3 cm down or half inches deep. With this, they have enough room to grow taproots. This might be one of the reasons your cannabis seed didn’t grow.

Using Old or Unsterilized Pots and Soils

A fungus is one of the greatest enemies that might affect the germination of cannabis seed. 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. For instance, a sprouting seedling might suddenly bend and change color to brown in a process known as damping off. This is common when you supply the seed with too much water when there is poor drainage or the aeration is poor.

Due to this, consider planting seedlings in a sterilized pot as the tendency of containing harmful organisms is low. Also, make sure the containers are clean as it can reduce the tendency of fungus.

Planting lots of Seed in one Pot

Planting a lot of seed in a single container might seem like a good idea due to the ability to save cost. This is like shooting yourself in the leg, as it might lead to a wasted effort. Even if the seeds germinate, they will compete for limited space, nutrients, and water. A cannabis plant needs enough space for its root to travel down without restriction to prevent severe intermodal distance.

Limited space translates to severe competition not only for nutrients but light as well. This is not a good idea if you want to get the best from your cannabis seed. If the seed eventually germinates, they will be weak, which will affect the plants and overall output.

Cannabis Seed left underwater for a long time.

Some growers prefer to soak their cannabis seeds before planting them. This is an essential step to break the dormancy and soften the shell to prepare the seed for planting. With a softshell, the taproot will easily break the body and push its way out of the shell. Typically, the seed will be put inside a glass of water and left until it sinks before the grower plants it. However, this is not as simple as it sounds.

A cannabis seed needs to be continually breathing, and a fully submerged seed will not get the necessary air supply. This might kill the seed if left for long inside the water. Once the seed sinks, take them inside the paper towel as soon as possible.


There are many intricacies involved in germinating a cannabis seed. Getting it wrong with any of the systems might not make the cannabis seed grow. You can arm yourself with these essential tips to ensure that your cannabis plants germinate. Use these tips as a guide when trying to germinate your cannabis seed. Also, if your seed does not germinate, this guide can help you troubleshoot.

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