What To Do With Weed Seeds

Many cannabis consumers have found an occasional seed in their bag of marijuana. But can you actually use them to grow your own weed? Learn more about germinating bag seeds and turning them into flourishing cannabis plants. Knowing how to store cannabis seeds is important if you want to keep your seeds over long periods of time – how long do marijuana seeds last? The fate of weed seeds in the soil has been an area of much research in recent years. Most studies have focused on the seeds that successfully produce seedlings since these are the seeds that cause immediate problems for farmers. In most studies, annual emergence typically accounts for 1 to 30% of the weed seed in the soil. Thus, the majority of seeds found in the soil seed bank fail to produce seedlings in any given year.

How to Germinate a Bag Seed

F inding a seed in your bag of weed used to be regarded as an insult, an indication you scored some inferior product. But it’s a new millennium, and growing cannabis is perfectly legal in some states and territories. While buying seeds online is still recommended for reasons we will detail further, finding a healthy seed can be as valuable as an ounce of gold. Or at least the cost of the bag.

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In this article we review the steps to germinate cannabis seeds, tips and tricks in the process, and how to keep your seedling healthy.

Germinating a seed is the first step in the growing process, and a cannabis seed will sprout with a voracious hunger, so if you are about to germinate seeds, start thinking ahead about where the seedling will eventually be moved to. This includes lighting, ventilation, and something to feed the lady. Those things don’t need to be decided before you begin, but try to have a plan in place by the time the second set of leaves emerges — as soon as two weeks.

The Germination Process

Begin by soaking the seed overnight. Soaking the seed saturates it with moisture, and moving it shortly after to a warm home tells the seed that it’s someplace comfortable, and it’s time to grow. Tap water is fine for this, but a micronutrient solution like liquid seaweed may be included.

Once your seed has soaked, the most common method for germination is the “paper towel method.” Wet a piece of paper towel and wring dry, then fold in half. Place the seeds between the halves of the damp paper towel, and slide the whole thing into a ziplock bag. Seal with some air inside. Leave this bag someplace comfortably warm for about a week, checking frequently for spots of mold. After about a week, a taproot should emerge.

Then it is time to transfer the seed into a proper growing medium. Be careful plucking your seed from the paper towel!

A grow medium is the “stuff” the seed will sit in. The easiest option is soil, healthy black earthy scooped up from your yard, or potting soil purchased from any garden center. Rock wool cubes are a common option for hydroponic growers, but can later be transplanted into soil as well. Compost and worm castings are great for a seedling, but it will need to be transplanted into a more diverse mixture later.

It is far too early to begin any nutrient cycle, or to introduce any fertilizers to the soil. Now that the seed is confirmed as alive, and placed into a more comfortable medium, simply make sure that the seed is watered and warm.

The first set of leaves to emerge are called “sucker leaves,” and their sole purpose is to drink in as much light as possible to fuel the growth of the more recognizable serrated leaves, which will begin to grow over the next week. After that you’ve got a proper seedling, and in a few weeks it will be ready for a bigger home!

For further guidance and resources about growing cannabis, see our Beginner’s Guide to Growing Marijuana, or our guide to growing for personal use.

Cultivating a Healthy Cannabis Seedling

The seedling that emerges will be as tender as an infant, and susceptible to diseases and cross-contaminations, so keep your germination station as sanitary as possible, and wash your hands before handling them. Avoid rubber or latex gloves at this stage as they have too much grip, and one wrong movement of your finger could accidentally grab and tear the soft plant material.

A seed’s health may be fortified by soaking it with a solution rich in micronutrients, like liquid seaweed. Be advised, however, that these will be very diluted solutions. Carefully read the mixing instructions of any product you purchase.

Seedlings can be protected against certain diseases by including worm castings in the medium. Research out of Cornell University has shown the microbial life in worm castings colonizes the seed’s surface, making it more difficult for pathogenic microbes to establish themselves.

Disclaimers and Downsides Regarding Found Seeds

It’s worth pausing to remember that seeds shouldn’t wind up in your bag of cured, smokable cannabis. So before planting anything, let’s assess what this seed is, and how it got there.

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Only female cannabis plants produce flowers, and if they are pollinated by male plants, then they produce seeds instead. So all the cannabis we smoke is from unpollinated female plants — or nearly all of it.

When female plants are stressed — for instance, by drought conditions or nutrient problems — an evolutionary alarm can induce them to produce seeds with only their DNA. The problem with these “hermaphrodite seeds” is that the offspring, having benefited from this process, will be more prone to repeat it. If this is how a seed got in your bag, it can result in seedy weed, even under the closest care.

A seed is not guaranteed to sprout at all. Examine the seed for any obvious health issues. Immature seeds are lighter greys-to-green, while mature seeds are darker tan, brown, or even black. A healthy shape is a teardrop or nearly round, while bunk seeds will appear shrivelled or irregular. Finally, healthy seeds have a hard, whole shell, while cracked or brittle shells will likely not sprout, or produce a less healthy seedling.

A found seed is also not a guarantee to produce a replica of the strain you smoked, and may present latent traits from the strains it was bred from. Cultivating a complete copy of a phenotype is called “cloning,” and the cloning process must begin with a living plant, not a seed.

Remember, it could also just result in a male plant, which won’t grow any buds. None of this is guaranteed to happen with a bag seed, it’s just more likely than with a stabilized seed from a producer.


If you want to germinate a seed you’ve found, begin by soaking it overnight in water to saturate it, and soften the shell. Micronutrient solutions can be mixed in at this stage to fortify the health of the seedling (if you do, be sure to read the mixing instructions on the label).

The “paper towel method” is the most accessible way of germinating almost any seed. Once a taproot has emerged (after about a week) plant the seed into a small container with your chosen grow medium, like soil. Do not fertilize at this stage, as the seed and resulting seedling are very tender, and concentrated fertilizers are abrasive chemicals. Within another week, “sucker leaves” will sprout, synthesizing light to produce further growth.

Remember, found seeds are not always healthy or even viable. A healthy seed has a hard, unbroken shell and a dark color, while brittle or misshapen seeds may not produce a healthy plant, if anything at all. A found seed is also not guaranteed to replicate the precise phenotype of that cannabis you found it in.

That said, it’s almost always worth trying, and experimenting with whatever results. Growing cannabis can be an enriching experience, and perhaps even save you some riches. As long as you know what to look for from a seed, and how to handle them, finding one in your bag could be a golden ticket.

How Long do Marijuana Seeds last?

When it comes to cannabis seeds, many first time growers tend to have some sitting around from an old friend or baggie. With recent legalization, new growers are deciding to dust their seeds off and start their very own grow, but how long do marijuana seeds last before they won’t germinate?

A typical feminized cannabis plant can produce an enormous amount of seeds – hundreds, depending on how well the plant takes the pollen and how meticulous the pollination process is. It also largely depends on the strain, as some strains are capable of producing much more, especially if their flowers are larger and can hold more. But how long do they last once they’ve been harvested and dried?

How Long do Marijuana Seeds Last?

There are many different factors that come into play when it comes to cannabis seed lifespan, and the most important is conservation. If you’ve obtained your seeds from a seed bank and they come in their own packaging, when it comes to storage you can simply leave them in their packaging in a dark, dry spot; seed banks usually recommend planting within the year.

However, if you’re planning on crossing your own plants and making your own seeds, you’ll need to know how to harvest, dry and store them if you’re planning on keeping them for a while before germinating them; knowing how to store cannabis seeds properly is quite an important tidbit of information if you’re a professional cannabis grower.

The seed is undoubtedly just as important as the final result; without quality seeds, you won’t get quality results. Keep in mind that cannabis seeds are practically living beings ready to be brought fully to life. Many new growers don’t know that cannabis seeds require specific care, and the way you store your seeds can significantly affect their outcome. Check out our Cannabis seeds – Buy Marijuana Seeds section to find reliable strains.

Drying Cannabis Seeds

When working from the start you’ll first need to pollinate the flowers on a female cannabis plant and then harvest the seeds once it’s fully matured. Once you have your seeds you’ll need to dry them out before they can be stored or even germinated – they should be ready to harvest once they’ve gone a dark brown color or start showing dark stripes. Most people opt to dry their seeds by simply drying the flowers and harvesting the seeds once they’ve dried out – it makes them much easier to remove from the flowers.

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How Long do Marijuana Seeds Last in Storage?

Once you have your seeds you’re going to want to store them correctly if you plan on using them down the line. In fact, when stored under perfect conditions, you can germinate 5 year old cannabis seeds successfully. Some astonishing cases have been reported of seeds lasting up to 10 years when stored optimally, although the germination times may vary wildly, taking much longer than a fresh seed. For home-growers, storing and maintaining seeds is quite important, and even more so for seed banks; a badly stored seed may not germinate, and if it does it may not grow properly. There are various parameters you’ll need to follow in order to store seeds long-term.

Seed Storage: Light

One of the first things to keep in mind is that whatever container that you store your seeds in needs to block out all light. If you’ve ever germinated cannabis seeds before, then you know that light is an important factor when it comes to the probability of the seed germinating or not. If your seeds are exposed to light for too long, they may end up too weak to germinate; even if they germinate they might have quite a hard time starting off.

Seed Storage: Temperature

The temperature at which you store your seeds is one of the most important factors. If you’re going for something short-term, you just have to make sure that they’re in an area with a stable temperature – do not store them somewhere where there are going to be temperature changes.

However, for long-term storage you’ll need to store them at around 6-8° – if you plan on storing a large amount of seeds, we recommend buying a small cooler for that specific purpose to keep them at a low, constant temperature; opening your fridge can cause temperature changes, so keeping them with the rest of your products is probably not the best idea.

Also, remember to use a blacked out container when storing in the fridge or a black bag to ensure that the lights inside don’t affect the seeds when opened.

Seed Storage: Humidity

Humidity is another incredibly important factor that can determine the success rate of your seeds. Relative humidity is essentially what causes seeds to germinate, so they’re quite delicate at this stage and you don’t want them accidentally germinating; keep relative humidity low in their container.

This obviously depends on your climate too, as there are places that have incredibly high humidity and others that are quite dry, which can directly impact how you have to store your seeds. As a general rule of thumb, we recommend keeping them in a low-humidity container, and if you live somewhere incredibly humid you might have to use specific methods to decrease humidity.

Cannabis seeds can germinate with a RH of 40-60%, and humidity higher than that can actually drown them and kill them. However, humidity ranging from 9 – 20% may also cause a myriad of issues such as insects, fungi, and even seed sweating due to excessive heat. The ideal humidity range in which to store your seeds is between 20 to 30% RH.

How Long do Marijuana Seeds Last

Taking into account the previously mentioned parameters, the best way to store your cannabis seeds for long periods of time is by vacuum sealing them and then putting them into an opaque container or bag so that no light gets to them. Keep them at a constant temperature of 6-8°. Some growers use products such as silica sachets to keep humidity down even if the outside temperature/humidity becomes drastically altered – this is a good idea if you live in more humid or hotter climates.

Keep in mind that if your seeds experience too much light or temperature changes they may end up using up their nutrient reserves, which would render them useless.

Fate of weed seeds in the soil

The fate of weed seeds in the soil has been an area of much research in recent years. Most studies have focused on the seeds that successfully produce seedlings since these are the seeds that cause immediate problems for farmers. In most studies, annual emergence typically accounts for 1 to 30% of the weed seed in the soil. Thus, the majority of seeds found in the soil seed bank fail to produce seedlings in any given year. The fate of seeds that fail to germinate and emerge is poorly understood. While some of these seeds are simply dormant and will remain viable until the following year, others are lost due to decay or consumed by insects or small animals. This article will describe results of an experiment that monitored the fate of seeds for the first four years following introduction into the soil.

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Methods: Seeds of velvetleaf, waterhemp, woolly cupgrass and giant foxtail were harvested from mature plants during the 1994 growing season. The seeds were cleaned and counted and then buried in the upper two inches of soil on October 21, 1994. Two thousand seeds were buried within a 3 sq ft frame to allow recovery during the course of the experiment. Weed emergence was determined by counting seedlings weekly during the growing season. Emerged seedlings were pulled by hand after counting. In the fall of each year one quarter of the soil within a frame was excavated and the remaining seeds were extracted and counted. Corn or soybeans were planted between the frames during the course of the experiment to simulate agronomic conditions.

Results: The emergence patterns of the four species were described in an earlier article (see emergence patterns). The fate of the seeds (emergence, loss or survival in soil) during the first four years after burial is shown in Figure 1. In the first year following burial waterhemp had the lowest emergence (5%) whereas greatest emergence was seen with woolly cupgrass (40%). Total emergence over the four years ranged from 300 seedlings (15% of seed) for waterhemp to 1020 seedlings (51%) for woolly cupgrass. More than three times as many seedlings emerged in the first year than in subsequent years for velvetleaf, woolly cupgrass and giant foxtail, whereas 140 waterhemp seedlings emerged in 1996 compared to only 100 in 1995.

Figure 1. Fate of seeds during the four years following burial in the upper two inches of soil. Two thousand seeds of each species were buried in the fall of 1994. The area in white represents the number of intact seeds present in the fall of each year, green represents the total number of seeds that produced seedlings during the four years, and the blue represents the total number of seeds lost. Buhler and Hartzler, 1999, USDA/ARS and ISU, Ames, IA.

Seeds of the two grass species were shorter lived than those of velvetleaf or waterhemp. At the end of the third year (1997) no grass seeds were recovered. Somewhat surprising is that waterhemp seed was more persistent than velvetleaf in this study. Velvetleaf has long been used as the example of a weed with long-lived seeds. In the fourth year of the study four times more waterhemp seedlings than velvetleaf emerged and four times more waterhemp seed than velvetleaf seed (240 vs 60) remained in the seed bank.

For all species except woolly cupgrass the majority of seeds were unaccounted for (the blue portion of the graph) in this experiment. Determining the fate of the ‘lost’ seeds is a difficult task. A seed basically is a storage organ of high energy compounds, thus they are a favorite food source of insects and other organisms. In natural settings more than 50% of seeds are consumed by animals. The importance of seed predation in agricultural fields is poorly understood, but recent studies have shown that predation can be a significant source of seed loss. Another important mechanism of seed loss likely is fatal germination. This occurs when a seed initiates germination but the seedling is killed before it becomes established. Fatal germination probably is more important with small-seeded weeds such as waterhemp and lambsquarters than with large-seeded weeds, but is poorly understood. A better understanding of the factors that influence seed losses might allow these processes to be manipulated in order to increase seed losses.

So what does this mean as far as managing weeds in Iowa. First, consider how the methods used in this experiment might influence the results. The seeds were buried in the upper two inches of soil, the zone most favorable for germination. Most long term studies investigating the persistence of seeds have buried the seeds at greater depths than used here in order to minimize germination. If the seeds were buried deeper one might expect less emergence and greater persistence since the seeds would be at a soil depth with less biological activity. If the seeds had been placed on the soil surface it is likely that there would be more predation, less emergence and shorter persistence.

The results indicate that the seed bank of giant foxtail and woolly cupgrass should be able to be depleted much quicker than that of the two broadleaves. Maintaining a high level of weed control for two years should greatly diminish populations of these weeds in future years and simplify weed management. Unfortunately, a single plant escaping control can produce more seed than was introduced to the soil in these experiments, thus the seed bank can be rapidly replenished any time weed control practices fail to provide complete control. Finally, over 50% of velvetleaf and waterhemp seed was lost in the first two years following burial. However, significant numbers of seed of these species remained four years after burial. This will make populations of these two species more stable over time than those of woolly cupgrass and giant foxtail.

Doug Buhler is a Research Agronomist at the National Soil Tilth Laboratory, USDA/ARS, Ames, IA.