Cannabis seeds 101: How to grow marijuana from seed
Cannabis is grown from one of two sources: a seed or a clone. Seeds carry genetic information from two parent plants and can express many different combinations of traits: some from the mother, some from the father, and some traits from both.
In commercial cannabis production, generally, growers will plant many seeds of one strain and choose the best plant. They will then take clones from that individual plant, which allows for consistent genetics for mass production.
If cannabis is legal in your state, you can buy seeds or clones from a local dispensary, or online through various seed banks.
Cannabis seeds vs. clones
For the typical homegrower, it may be easier to obtain cannabis seeds rather than clones. Growing from seed can produce a stronger plant with more solid genetics.
Plants grown from seed can be more hearty as young plants when compared to clones, mainly because seeds have a strong taproot. You can plant seeds directly into an outdoor garden in early spring, even in cool, wet climates.
If growing outside, some growers prefer to germinate seeds inside because they are delicate in the beginning stages of growth. Indoors, you can give weed seedlings supplemental light to help them along, and then transplant them outside when big enough.
Most seeds that you will buy are regular seeds as described above, but here are a couple more types.
How weed seeds work
Cannabis can be either male or female—also called “dioecious”—but only females produce the buds we all know and love. For reproduction, males have pollen sacs and pollinate females, causing female flowers to produce seeds.
Once cannabis seeds are mature, the female plant begins to die, and seeds are either dropped to the ground where they grow into new cannabis plants next spring, or the seeds are harvested for processing into seed oil or food products, or stored so they can be sown in the ground later and become the next generation of plants.
To get the buds found in medical and recreational stores, female cannabis plants are grown in an environment without males—or the males are removed from the area before they release pollen—so the females don’t create seeds. Females can then focus their energies on producing buds and not seeds—this high-potency marijuana is traditionally known as “sinsemilla,” meaning “seedless.”
Some varieties of cannabis can produce male parts alongside female flowers on the same plant, especially if exposed to environmental stressors. These plants are known as hermaphrodites, and sometimes they can self-pollinate to create seeds.
Pros and cons of using cannabis seeds
Check out Johanna’s full video series on how to grow weed on Leafly’s YouTube .
If buying from a reputable breeder or seed bank, growing from seed is the best way to ensure your plants will have solid genetics and start clean, meaning they won’t come with diseases or pests.
Also, buying from a reputable breeder or seed bank will give you a sense of what a particular strain will look and smell like, how it will grow, and how much it will yield at harvest.
The main drawback to growing from seed is there is no guarantee as to what you’ll end up with—if you buy a regular pack of cannabis seeds, it will be a mix of males and females. You’ll need to sex them out (more below) to identify the males and get rid of them, because you don’t want your females producing seeds.
Sexing marijuana plants can be a time-consuming process, and if you don’t catch males, there is a risk that even one males can pollinate your entire crop, causing all of your female weed plants to produce seeds.
One way to avoid sexing plants is to buy feminized seeds (more below), which ensures every seed you plant will be a bud-producing female.
You can also minimize headaches and avoid the hassle of seed germination and sexing plants by starting with clones.
How weed clones work
Aside from producing cannabis through seeds, or sexual reproduction, you can also reproduce the plant through cloning, or asexual reproduction. A clone is a cutting that is genetically identical to the plant it was taken from—that plant is known as the “mother.”
Pros and cons of using cannabis clones
Through cloning, you can create a new harvest with exact replicas of your favorite plant. Because genetics are identical, a clone will give you a plant with the same characteristics as the mother, such as flavor, cannabinoid profile, yield, grow time, etc. So if you come across a specific strain or phenotype you really like, you might want to clone it to reproduce more buds that have the same effects and characteristics.
With cloning, you don’t have to get new seeds every time you want to grow another plant—you just take a cutting of the old plant—and you don’t have to germinate seeds or sex them out and get rid of the males.
One drawback of clones is they need to be taken during the vegetative stage of a plant—flower is too late—so if you have a small setup with only one light, it can be hard to keep clones alive while flowering other plants, because the two need different amounts of light.
Another drawback to clones is they can take on negative traits from the mother plant as well. If the mother has a disease, attracts pests, or grows weak branches, its clones will probably have the same issues.
Additionally, every long-time grower will tell you that clones degrade over time.
What are feminized cannabis seeds?
Feminized cannabis seeds will produce only female plants for getting buds, so there is no need to remove males or worry about female plants getting pollinated. Feminized seeds are produced by causing the monoecious condition in a female cannabis plant—the resulting seeds are nearly identical to the self-pollinated female parent, as only one set of genes is present.
This is sometimes referred to as “cloning by seed” and will not produce any male plants. This is achieved through several methods:
- By spraying the plant with a solution of colloidal silver, a liquid containing tiny particles of silver
- Through a method known as rodelization, in which a female plant pushed past maturity can pollinate another female
- Spraying seeds with gibberellic acid, a hormone that triggers germination (this is much less common)
Most experienced or commercial growers will not use feminized seeds because they only contain one set of genes, and these should never be used for breeding purposes. However, a lot of beginning growers start with feminized seeds because they eliminate the worry of having to deal with male plants.
Top feminized cannabis strain families
A lot of classic weed strains that have been around for a while come in feminized form. Some popular fem seeds are:
- OG Kush
- GSC (Cookies)
What are autoflowering cannabis seeds?
Autoflowering seeds are also popular with beginning growers. They are easy to grow because you don’t have to worry about light cycles and how much light a plant receives.
Most cannabis plants begin flowering when the amount of light they receive on a daily basis reduces. Outdoors, this happens when the sun starts setting earlier in the day as the season turns from summer to autumn. Indoor growers can control when a plant flowers by reducing the daily amount of light plants receive from 18 hours to 12 hours.
However, a type of cannabis called Cannabis ruderalis, which developed in extreme northern conditions without much sunlight, will begin flowering once the plant reaches a certain age—they automatically start flowering regardless of the amount of light they receive, hence the name “autoflower.”
Pros and cons of growing autoflower
Because they grow and flower quicker, growers can fit in multiple autoflower cannabis harvests into the span of one regular harvest.
Autoflowers can be started in early spring and will flower during the longest days of summer, taking advantage of high quality light to get bigger yields. Or, if you get a late start in the growing season, you can start autoflowers in May or June and harvest in the fall.
Also, autoflower plants are small—perfect for closet grows or any small grow, or growing outdoors where you don’t want your neighbors to see what you’re up to.
A couple big drawbacks, though: Autoflower strains are known for being less potent. Also, because they are small in stature, they usually don’t produce big yields.
However, potency in autoflowering varieties has increased significantly since their initial introduction, with some breeders crossbreeding the low-THC ruderalis with other more potent varieties.
Tips for growing autoflower marijuana seeds
Autoflowering strains require some preparation, as they will grow quickly and start to flower whether or not you’re ready for them.
Many marijuana growers start autoflowers early in the season, and at a different time than a regular crop, so keep the season and climate in mind when growing and harvesting—your plants still need warmth to grow, and rain can give them bud rot. Consider growing in a greenhouse to protect them.
Because training happens during vegetative growth, for autoflowering plants, this period could be as short as a few weeks, which means time is limited. Try topping your autoflowers after they have three nodes, and stop once they begin to flower. You will want to prune them lightly.
Go easy on nutrients
Autoflowers don’t need lots of nutrients because they’re small and don’t spend much time in the vegetative cycle. They won’t need as much veg nutrients—such as nitrogen—but will need more bloom nutrients.
What are high-CBD cannabis seeds?
CBD, or cannabidiol, is one of the chemical components—known collectively as cannabinoids—found in the cannabis plant. Over the years, humans have selected plants for high-THC content, making cannabis with high levels of CBD rare. The genetic pathways through which THC is synthesized by the plant are different than those for CBD production.
Cannabis used for hemp production has been selected for other traits, including a low THC content, so as to comply with the 2018 Farm Bill. Consequently, many varieties of hemp produce significant quantities of CBD.
As interest in CBD as a medicine has grown, many breeders have crossed high-CBD hemp with cannabis. These strains have little or no THC, 1:1 ratios of THC and CBD, or some have a high-THC content along with significant amounts of CBD (3% or more).
Seeds for these varieties are now widely available online and through dispensaries. It should be noted, however, that any plant grown from these seeds is not guaranteed to produce high levels of CBD, as it takes many years to create a seed line that produces consistent results. A grower looking to produce cannabis with a certain THC to CBD ratio will need to grow from a tested and proven clone or seed.
How to germinate marijuana seeds
Germination is the process in which a seed sprouts and begins to grow into a new plant. Also referred to as “popping,” germination is the very first step in starting your weed grow.
Marijuana seeds can be acquired from an array of sources and can vary in quality. For more info on how to buy marijuana seeds, check out our Guide to buying cannabis seeds.
Cannabis seeds require three things to germinate: water, heat, and air. There are many methods to germinate seeds, but for the most common and simplest method, you will need:
- Two clean plates
- Four paper towels
- Distilled water
Take four sheets of paper towels and soak them with distilled water. The towels should be soaked but shouldn’t have excess water running off.
Take two of the paper towels and place them on a plate. Then, place the marijuana seeds at least an inch apart from each other and cover them with the remaining two water-soaked paper towels.
To create a dark, protected space, take another plate and flip it over to cover the seeds, like a dome.
Make sure the area the seeds are in is warm, somewhere between 70-85°F.
After completing these steps, it’s time to wait. Check the paper towels once a day to make sure they’re still saturated, and if they are losing moisture, apply more water to keep the seeds happy.
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. The sprout is the taproot, which will become the main stem of the plant, and seeing it is a sign of successful germination.
It’s important to keep the delicate seed sterile, so don’t touch the seed or taproot as it begins to split.
Transplanting germinated cannabis seeds
Once you see the taproot, it’s time to transfer your germinated seed into its growing medium, such as soil.
- Fill a 4-inch or one-gallon pot with loose, airy potting soil
- Water the soil before you put the seed in; it should be wet but not drenched
- Poke a hole in the soil with a pen or pencil—the rule of thumb is: make the hole twice as deep as the seed is wide
- Using a pair of tweezers, gently place the seed in the hole with the taproot facing down
- Lightly cover it with soil
Keep a close eye on the temperature and moisture level of the soil to keep the seed happy. It’s very delicate at this stage. Use a spray bottle to water it—over-watering can suffocate and kill the delicate sprout.
Within a week or so you should see a seedling begin to grow from the soil.
Germinating cannabis seeds doesn’t always go as planned. Some seeds will be duds. Others will be slow and take longer to sprout. But some will pop quickly and grow rapidly.
This is the beauty of seeds—often, you can tell which plants or genetics will thrive right from the get-go. This will help you determine which plants you want to take cuttings from for clones or for breeding if you want to create a seed bank of your own.
How to sex a pot plant
Check out Johanna’s full video series on how to grow weed on Leafly’s YouTube .
As we’ve mentioned, cannabis is a dioecious plant, meaning male and female reproductive organs appear on different plants.
Because only female cannabis plants produce buds and you want them to focus all their energy on producing buds and not seeds, it’s important to identify and get rid of male weed plants so they don’t pollinate females. If females are pollinated, it will give you buds filled with seeds, making your weed harsh and unpleasant.
Cultivating males is important for breeders trying to cross new strains and genetics, but most people growing for buds will want to remove the males.
As mentioned above, you can skip the processing of sexing weed plants by growing with feminized seeds or clones.
If growing male and female cannabis seeds, they’ll start to show their sex organs, or “pre-flowers,” after 8-10 weeks from germination.
Cannabis plant sex organs appear on nodes, the points where branches grow off from the main stalk.
Males will have round balls—these will develop into pollen sacs, which will release pollen into the air when mature.
Females will have a round structure with long hairs—these hairs will develop into pistils, which will catch pollen in the air.
Pre-flowers can initially be extremely small and hard to identify with the naked eye, but you can use a magnifying glass to get a better look.
Can I grow a seed I found in a bag of weed?
Finding a cannabis seed in your stash is not ideal, but we’ve all been there before. Although much less common than it once was, it still happens. Sometimes you’ll notice one when grinding down some flower, or you’ll see one pop, spark, and crackle from the heat of a lit bowl.
These are referred to as “bagseeds” and whether or not you can grow one will depend on where it came from.
Is a bagseed good or bad?
Seeds found in finished cannabis buds can develop for a number of reasons. For example, a male plant may have accidentally pollinated a flowering female during the growing process. But more commonly, they’re a sign of stress and can be attributed to high temperatures during the final stages of flowering or an exaggerated spike in climate or environment.
Seeds can also form in plants with genetic disorders or instability, like hermaphrodites—plants that develop both male and female reproductive parts. Generally, stress and genetic disorders are viewed as bad, so temper expectations with any plant you start from a bagseed.
But sometimes you get lucky and find a mature seed in some really nice herb. Strains like the legendary Chemdog wouldn’t be possible without adventurous smokers planting and proliferating the seeds they found in a bag of kind bud.
So don’t discount bud because it has a seed or two in it. While not ideal, it could be the origins of the next great weed strain.
Ask yourself a few questions to decide if it’s worth the time and energy to grow the seed.
Was the seed found in good weed?
If you don’t like the flavor, effects, or even the look of the bud, then it’s probably not worth growing.
Are you ready to grow?
Growing marijuana takes a certain level of commitment: time, energy, and financial resources, so be sure you can commit to the whole process.
Is the seed viable?
For a seed to be viable, it must be mature enough to have a completely formed genetic blueprint, and it must be strong enough to germinate and pop through its hard casing and sprout its crucial taproot.
There are a few indicators that will give you a sense of whether the seed is worth germinating.
- Tiger stripes—dark stripes on the seed which resemble veins on a leaf are generally good
- Solid shell—a seed should be able to withstand a little pressure when pinched between your fingers; if it crumbles or cracks, it’s no good
Immature seeds tend to be light in color and have a soft outer shell.
In some cases, even if a seed isn’t completely mature, there’s still a chance it could be viable. But often these are extremely weak, take long to develop, and express other unfavorable characteristics. Growers usually discard weak plants to free up space.
You might also find a mature seed that has been physically damaged through poor handling, like rough trimming. In those cases, it probably isn’t worth the effort to try and germinate the seed.
But if the seed you found looks decent, you might as well germinate it and see what sprouts.
Time to germinate
Viable or not, there’s only one sure way to find out if a bagseed will grow. If you’re simply curious to learn and not as concerned with the overall outcome, you can plant a couple of bagseeds outside and see what happens.
If you’re ready for a more serious approach, make sure you have the space for a proper garden and pop the seeds to see what fruit they bear.
Even if your seed sprouts fast and grows vigorously, it still has roughly a 50/50 chance of being female and producing buds, instead of turning out to be a male.
Remember, once a seed germinates, the real work begins. Sexing, selecting, vegetative growth, flowering, and the eventual harvest all lie ahead.
How to buy cannabis seeds
Cannabis seeds can be found on numerous online seed banks, but note that it is illegal to bring seeds into the US and Customs will seize any cannabis seeds that they find in packages or on a person. In legal and medical states, you may purchase seeds at a dispensary.
Will Hyde and Trevor Hennings contributed to this article.
Want to grow weed from seeds? Learn how weed seeds work, how to sex marijuana plants, and how to properly germinate your cannabis seeds.
How To Make Feminized Cannabis Seeds Like The Pros
Growing from feminized cannabis seeds is a space and resource-efficient way of getting all girls, all the time. Find out how to create your own feminized cannabis with Royal Queen Seeds.
MAKING FEMINIZED SEEDS
Growing cannabis is all about resinous flowers, trichomes, and rich cannabinoid profiles. These splendid characteristics can only be found on the female flowers. Having gardens full of robust, un-pollinated sinsemilla females means jars full of mind and body-friendly, crusty nuggets.
The only bummer, unless you grow from clones, is that cannabis is wired to produce about 50% male seeds and 50% females. It is just the nature of the beast.
Wouldn’t it be sweet if it was possible to grow all females from seed, every plant, every time?
Well, that is where the feminizing technique comes into play: two methods of manipulating the cannabis plant to produce only females from seed, every-time. To be truthful, it isn’t every single time. But 99% of the time is a pretty good number, and could be considered entirely male risk-free.
The general practice behind feminization is that female plants are forced to produce pollen, which is in turn used to pollinate other female plants. The outcome? Resulting seeds will be feminized, with no risk of further pollination.
Feminized seeds are super efficient for indoor and outdoor gardeners. Area, time, and resources aren’t being given to plants that will be thrown away two weeks after the 12-12 flip. Similarly, outdoors where a large plant can consume a lot of time and resources in upkeep prior to the autumn show of flowers, feminized plants are also a good way to reduce guerrilla crop pollinating. There’s nothing worse than bush-bashing out to a well-hidden crop only to find a rogue male or two have impregnated every female plant.
INHIBIT THAT ETHYLENE
“Applications that reduce the ethylene level in tissues or antagonise the action of ethylene causes the formation of male flowers instead of female ones” — Paraphrase, Byers et al., 1972.
There are a number of solutions that can be sprayed on female plants to create male pollen sacs: benzothiadiazole, gibberellic acid, silver thiosulphate, silver nitrate, and colloidal silver.
Colloidal silver is by far the easiest to source or make. It is non-toxic, non-caustic, and can be bought from a pharmacy or easily online. The other solutions can be dangerous, difficult to get a hold of, and expensive—except gibberellic acid, which can be found in nurseries, but is not as effective as colloidal silver. But if you want to watch some freaky plant growth just for the fun of it, give gibberellic acid a try. It is a growth stimulant and makes plants stretch and stretch.
TECHNIQUE 1: COLLOIDAL SILVER
Colloidal silver is a distilled water-based solution in which microscopic particles of silver are suspended. The nature of colloids means the particles will never settle out and can’t be removed by normal filtering. Colloidal silver is available commercially, or you can make your own if you want to totally geek out (see how-to section at the end). It has numerous uses as an alternative medicine. For example, it is used to soothe burns, as an antiseptic and digestion stimulant in people, and as a fungal control in horticulture.
Be sure the strength is at least 15ppm, preferably 30ppm. Less than 15ppm produces male sacs with little viable pollen.
To begin with, select a plant that has the characteristics you want to preserved. Feminizing clones is the usual practice as the growth, flowering, and resin characteristics from the mother are already known. There is no need for any vegetation time once a clone is well-rooted. Simply pot the clone into a small pot, give it a day or two to recover, and begin a 12-12 light cycle right away. A pollen-producing plant only needs to be small as cannabis produces copious amounts of pollen.
Hint: Make two clones once a plant has been selected, one to be feminized and one to be left for pollination. This way, a separate breeding space is created and accidental seeding of other plants, or an accidental sneeze pollinating a whole grow cupboard, is avoided.
Plants can be induced to grow male sex organs as late as four weeks into flowering. Though spraying one week prior to the light changeover is recommended for clones. If a plant grown from seed is being used, wait until the plant has sexed before spraying so you can be sure it is female.
Spray the plants to be feminized with colloidal silver every day, and three times a day if you can manage. Soak them well. Do this for two weeks, then leave the plants to grow as normal. Some growers report getting results after spraying for only 5–10 days.
When sexing begins, male pollen sacs will develop instead of female calyxes and pistils. Male plants mature much faster than females, and viable pollen can be expected within 3–4 weeks once the plant has been sexed. Some growers will spray until the plant shows sexual growth, just to be sure the method has worked. Make sure these plants are well-isolated from any flowering females. A burst pod can release millions of pollen spores, and it only takes one spore per hair to create a seed.
DON’T SMOKE IT
Once the plants have been sprayed with colloidal silver and the pollen is collected, they are write-offs—86 them and don’t smoke them. Giving them a thorough rinse will not work. The colloidal silver is a systemic treatment absorbed into the plant through the foliage and not a topical application. Be safe and bin them.
TECHNIQUE 2: RODELIZATION
Sinsemilla is an unnatural state for cannabis. Without human intervention, it would be rare to find an unpollinated female in the wild—unless it was sterile. When sinsemilla plants are left to go beyond their desirable maturation stage by a number of weeks, the plant, through whatever amazing processes evolution has bestowed, knows it has not been pollinated. As a last ditch effort at propagation, it will produce male pollen sacs in an effort to self-pollinate.
This is not the result of genetic or stress-induced hermaphroditism. They are genuine XX chromosome male bananas. With all the genetic information from the female and no Y chromosome, using rodelized pollen creates female-only seeds, although as with colloidal silver, an occasional male may appear.
HARVESTING POLLEN AND POLLINATION
There are a number of harvesting methods employed to catch pollen.
- Cover the top of the pot with plastic or card to catch pollen as it falls, or modify a plastic drink cup to shroud the plant and catch falling pollen.
- Fix a clear plastic bag, perforated at the top for air exchange, around the whole plant.
- An experienced eye will remove each flower pod prior to it bursting completely open to be sure of catching every spore.
- Pollinating a female is the easy bit. Depending on how many seeds you want to make, there are a couple of methods that can be used.
- Using a watercolour or other fine, soft brush or even a cotton bud, dip into your pollen collection and gently apply to the chosen flower. Although thousands of viable spores will be on the end of the brush, enough to pollinate a whole plant, the trichomes on the surface of the pistils will greedily glue everything you offer them. So dip into your pollen stash a few times as you dust.
- For lots of seeds, put pollen in a bag and put over a whole branch or a whole plant, shake well, and leave for twenty four hours.
- It is possible to pollinate different branches with different pollens and have a breeder plant that has 1, 2, or 15 different crosses on it.
- It is also possible to self-pollinate the plant from which the male parts were created. This won’t produce as many seeds as pollinating a separate plant because less female flowers are produced and many are nonviable because of the feminization process.
GROWING FEMINIZED PLANTS
Treat feminized seeds as you would any other seed from germination to veg, and veg through flower. Observation is where it’s at now, you want the best plants for your garden. Ideally, setting up a separate vegetation/flower space where a number of plants can be grown lets your standard grow space continue with uninterrupted production.
Plants bred using feminization are homozygous. This can have two effects that can’t be assessed until the seeds are grown. Homozygosity will increase the dominant or recessive traits of the parent in the progeny, so features you don’t want and do want can be amplified. Genetics is a weird, weird thing.
Just as with standard male to female crossings (which is a heterozygous process), a number of plants will need to be grown and the best selected for mother plants and future breeding. With enough room, hundreds if not thousands of new plants can be grown in order to select the best of the best phenotypes.
With a bit of aforethought, it is possible to set up an efficient feminization breeding programme—and have female seeds from your favourite phenos on hand all the time. You never know, you might discover the next big thing!
MAKING YOUR OWN COLLOIDAL SILVER
The easiest and relatively inexpensive way—considering how much money is potentially saved by not growing resource and time-consuming males—is to buy a colloidal silver generator, which is the no-fuss plug and play option. Or, make your own, which is quite straightforward and doesn’t require any special skill.
Colloidal silver is formed by passing a current from a pure silver electrode through distilled water. This simple electrolysis is all there is to it. Although distilled water does not conduct electricity very well due to its lack of mineral content, enough is passed through to create micro silver particles and silver ionisation. Sounds technical, but it really isn’t.
Feminized cannabis seeds only produce female plants, which has a number of advantages. Find out how to do it with Royal Queen Seeds.