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.
How do I germinate marijuana seeds?
Cannabis germination is the process of getting your seeds to sprout, and you know sprouting has occurred when a little white tendril pops out of the seed.
The little white tendril that emerges from a cannabis seed during germination is your plant’s first root, known as a “taproot.” All other roots made by your cannabis plant in its lifetime will sprout from the taproot.
The taproot – and maybe a few tiny early offshoots of the taproot – will get longer and longer, pushing the seed up, and after the shell breaks through the surface of your growing medium, the first leaves (these first round leaves are known as “cotyledons”) will emerge from inside the cannabis seed.
The cotyledons were already created as part of the plant embryo in the seed itself, so the cannabis seedling doesn’t have to grow them. In fact, the emerging first leaves are what break apart the shell after it’s cracked open by the taproot, as pictured here.
The next set of leaves after the cotyledons are your plants first “true” leaves and will have jagged edges (serrations). At least, they are the first leaves that your seedling cannabis plant has grown all on its own, unlike the cotyledons which were already formed in the seed.
Cannabis seeds can be expensive, don’t waste your seeds with bad germination methods!
(Wait, where can I get cannabis seeds?)
What Do Marijuana Seeds Need to Germinate?
Marijuana seeds need the following to get the best germination rates:
- Moisture – Keep things moist but not soaking (you can soak hard seeds for up to 24-32 hours, but do not leave seeds soaking in water for longer than that).
- Peace – Seeds need to be left alone while you’re waiting for the taproot to show up.
- Warmth – Keep things warm to get the best germination rates, but not too hot! Think springtime. Seeds can definitely germinate in cooler temps, but germination tends to take longer when it’s cool.
- Gentle – Be careful when checking seeds, and treat them gently when you have to move them. Avoid touching their white root if possible; the taproot is very fragile and easily snaps off!
- Plant Root Down – When planting germinated seeds, point the white root downwards into the growing medium to prevent the seedling from having to reorient itself.
- Plant Knuckle Deep – When planting germinated seeds, they don’t have to be placed too far under in the growing medium, about a half inch to an inch (1.3 cm – 2.5 cm) down from the surface of the medium should be enough.
When germinating cannabis seeds, think springtime conditions. In the wild, your cannabis seeds would germinate in the spring so they can be ready to take full advantage of long summer days!
Never let your young sprouted seeds dry up!
The main signal that tells a marijuana seed to start sprouting is the presence of moisture and heat. The combination of warm and wet (aka spring conditions) “tells” the seed to start burrowing their main root (called a taproot) through their shell.
If a seed’s root breaks through the shell and the water around has dried up, your seedling will die. Plain and simple.
Seedlings are fragile at first. Once sprouted, the roots need to stay constantly moist to stay happy and healthy. It’s important to make sure the seeds have access to water the entire time during germination, no matter which cannabis germination method you end up using.
Keep things warm!
Seeds germinate best in warmer temperatures and young marijuana seedlings do better with higher relative humidity in the air. When seedlings are young, they grow faster and healthier when they can absorb moisture from the air through their leaves while their roots are still developing. Dry air won’t kill your seedlings, but it doesn’t make things better. Again, think springtime conditions!
You can use an incandescent bulb (or two) placed over the marijuana seed germination area to help keep things warm. Incandescent bulbs are the opposite of what a grower typically wants: they can’t be used as grow lights, but they’re great at generating heat. Some people will also place a heating pad (the kind you get from a garden store for seedlings) underneath seeds to help aid germination.
Basically, you want to make sure any seeds or sprouts are kept warm and moist at all times, that their roots are unexposed to light, and that they get planted right away.
There are several different methods to germinate your cannabis seeds, and in this article we’ll go through some easy techniques that have proven to be effective.
How do I know if my seeds are good?
Assume all dark seeds are viable, even if seeds can be crushed
Generally, pale-green or white seeds will not germinate, but most dark seeds will germinate when given good conditions.
I used to believe that marijuana seeds were only “good” if they were extremely hard and very dark. One of the first tests I heard to check new cannabis seeds for viability was to try to crush them between my fingers. If the seeds could be crushed, they weren’t good, or so I was told. This has proven to be absolutely terrible advice!
Some of the best plants I have ever grown have emerged from seeds which were flimsy and could be crushed between my fingers. As long as you provide great marijuana germination conditions (as explained above), I’ve found that a lot of seemingly “weak” seeds germinate and produce amazingly hardy plants and great buds.
I do not believe the health of the plant is directly tied to the apparent “health” of the seed. If the seed germinates, it’s a good seed!
Here’s a picture showing several healthy and viable cannabis seeds
Remember! Most of the medical strains of marijuana we grow today (learn how to get seeds) have been bred over many years to produce plants that are easy to grow and which produce potent, medicinal buds. However, these strains have not been selected for the toughness of the seeds they produce since that isn’t important to us as growers. Just remember…
As long as a seed germinates, it’s a good seed!
Germination Method 1: Starter Cubes & Seedling Plugs (Recommended)
One of the best cannabis germination methods is to use specifically-made starter cubes and seedling plugs. These plugs make cannabis germination easy. You simply place the seed in the cube or plug, add water as directed, and seedlings automatically get the perfect conditions for germination.
Each cube or plug already has a hole specifically for you to place your seed. Just stick your seed into the precut hole and pinch the top closed a bit with your fingers. Don’t worry, you can’t mess this part up As long as the seed makes it in there, you should be good.
This is one of the easiest germination methods and doesn’t leave a lot of room for error. Cannabis seeds and clones can be expensive, and sometimes we have genetics we just can’t afford to lose. When that’s the case, germinate your cannabis with one of the following recommended options to ensure as close to 100% germination rate as possible.
Which Starter Cubes Work Best for Germinating Cannabis?
Rapid Rooters (Highly Recommended For All Setups)
Rapid Rooters are easy to work with – you just stick your cannabis seed in the Rapid Rooter (pointy side down), keep your seed warm and slightly moist, and let the Rapid Rooter do its magic.
Sprouts emerge and roots appear in just a few days.
Rapid Rooter starter cubes are suitable for all growing methods, including hydroponics, coco coir and soil. They work for every setup and come from General Hydroponics, a trusted company (the same one used by NASA) which is known for the quality and consistency of its products.
I highly recommend using Rapid Rooters over any other starter plugs. They are less prone to problems and work great with any growing medium (including hydroponic systems).
Pros of Rapid Rooters
- Easy to Use – You Can’t Really Mess Up
- No Prep or Setup – Open the Package and Go
- Some of the Best Germination Rates of Any Method
Cons of Rapid Rooters
- Can only get 50+ at a time (General Hydroponics currently does not offer fewer plugs per package)
- After opening the package, you only have a week or two before they dry out, so if you’re only germinating one or two seeds, you’ll end up having to throw many of the Rapid Rooters away.
There are a few different options for Rapid Rooters, which can be confusing if you’re not sure what you want. The 3 different options for Rapid Rooters are listed here…
Bag of Rapid Rooters
These are round on bottom instead of being a cube, which means they cannot stand up on their own. These are best suited to a hydroponic setup where the Rapid Rooter will be placed directly in the final destination. In our hydroponic setups, we’ve had near 100% germination rates with Rapid Rooters, better than any other seedling cube we’ve tried.
- Round on bottom (won’t stand up by themselves without support) unless you squish the bottom so it’s flat like this grower did (pic)
- Great for starting with Rapid Rooter directly in final destination (hydro, soil, coco coir, etc)
- Get 50 Rapid Rooters at a time
Rapid Rooters Mat
This type of Rapid Rooters comes in a mat of (usually 98) Rapid Rooters. All the individual Rapid Rooters are sectioned off and have a hole for the seed, but they must be cut or pulled away from the complete mat. Unlike the type of Rapid Rooters that comes in a bag, these ones are made into cubes and are flat on the bottom so they can stand alone. This makes them good for germinating in a shallow pool of water where the cubes need to be able to stand up on their own.
- Easily break cubes off the mat (already sectioned off with pre-cut holes)
- Already shaped like cubes with flat bottoms, so they easily stand up by themselves
- Good for seamlessly transplanting your seedlings somewhere else
- Get 98 Rapid Rooters at a time
Rapid Rooters Tray
The Rapid Rooters tray is perfect for seeds or clones. Allow your young plants to sit in the tray with water until their roots are well formed and ready to be transplanted to your final destination. The standard size tray fits most humidity domes. You can refill the tray with Rapid Rooters from the bag or mat.
As you can see in the pictures below, the Rapid Rooter Tray comes packaged up. Once you open the package, you will see 50 Rapid Rooters already set in the tray. The resting place for each Rapid Rooter has a hole on the bottom so water within the tray is wicked up. The top part comes apart from the bottom.
Just add you seeds and pour some water into the tray – the Rapid Rooters will do everything else for you.
- Perfect for cloning or starting seeds with a humidity dome (standard 10-inch by 20-inch dome like this one – 7-inch height recommended for cannabis seeds or clones)
- Easy to transplant to new destination
- Just add water and seeds, that’s it!
- Whole tray can be refilled with any type of Rapid Rooters (from bag or mat)
- Comes with 50 Rapid Rooters, ready to go
Rockwool Cubes (Not Recommended)
It’s often hydroponic cannabis growers who use Rockwool cubes since these can be safely placed in hydroponic setups, hold a lot of moisture, and are resistant to mold. Rockwool is cheap and easy to find. It comes in convenient cubes. But it does have some major drawbacks…
Pros of Rockwool
- Cheap & Easy to Find
- Inert Medium (useful for hydroponic growers)
Cons of Rockwool
- Bad for the environment (unnatural material that does not break down)
- Bad for your health (especially your lungs) – wear gloves and cover your mouth/eyes when handling Rockwool
- Has a pH that is too high for cannabis, so it must be thoroughly rinsed and treated
- Poor cloning and germination rates
- Difficult for new growers
Rockwool cubes are bad for the environment
Rockwool is not a natural material – it’s made by heating rock and chalk to 3,000°F and air is blown through the mixture to create thin fibers of rocky material
It does not break down naturally and therefore after Rockwool is created, it will remain in that form basically forever, filling up landfills without breaking down for thousands of years.
Rockwool cubes can be bad for your health
Rockwool is dusty and needs to be rinsed thoroughly before use. Little pieces of Rockwool and dust can easily get in your eyes, skin and mouth. Small strands or fibers can get lodged in your lungs if you breathe in Rockwool dust, and it’s unknown if these fibers can ever get out again.
Protect yourself! Always use a mask, goggles and gloves when working with Rockwool.
Rockwool cubes have a high pH until they’re treated
New Rockwool cubes have a high pH – too high for healthy cannabis seed germination. Therefore it’s important to thoroughly rinse Rockwool cubes in pHed water, then let them soak in pHed water overnight before use. Since Rockwool holds onto a lot of water, after soaking they should be given a few days to dry out before planting seeds or making clones.
Rockwool cubes do not get great germination rates
Rockwool can be difficult to germinate marijuana seeds in, so I recommend most beginner growers sprout their seeds using another method like Rapid Rooters (mentioned above) which can also be used in hydroponic applications but are less prone to germination problems.
Many growers have placed seeds in Rockwool cubes, only to wait for weeks and never see seedlings appear.
Some growers seem to have no problems, yet many other growers suffer through very poor germination rates. Some seed companies will not honor seed germination guarantees if the grower uses Rockwool because it is notoriously bad for germination.
If you do use Rockwool, it’s recommended you germinate your seeds using another method like the paper towel method, then transplant your seeds to the Rockwool cubes after roots have already appeared.
Even when following all the best practices, we just have not gotten great germination rates with Rockwool cubes, and it’s common for new seedlings not to make it. When we were using Rockwool (before we switched to Rapid Rooters), we usually lost at least 1 seed out of a batch of 6 or 8.
We also had trouble rooting clones in Rockwool. Rockwool cubes just don’t hold enough air to get plenty of oxygen to the roots, and they tend to hold onto a lot of water and get waterlogged easily. Since Rockwool can hold a lot of water, it’s prone to “drowning” seeds
I highly recommend using Rapid Rooters instead for your hydroponic application (or any grow setup), as they are much more user-friendly and tend to get far better germination rates.
Jiffy Pellets (Recommended for Soil or Coco Coir)
Jiffy Pellets are used in a similar way to Rockwool cubes, though these tend to get much better germination results. Jiffy pellets are not suitable for most hydroponic setups where the roots are grown directly in water, but Jiffy Pellets can be directly transferred into soil or coco coir.
Pros of Jiffy Pellets
- Good Germination Rates for Soil and Coco Coir
- Good for Cloning – read a cannabis cloning tutorial using Jiffy pellets
- Come in dried pellets, so they can be kept for a long time
Cons of Jiffy Pellets
- Not suitable for hydroponic setups
- Must be soaked to expand each pellet before use
How to Use: Soak Jiffy pellets in warm water, which makes the pellets expand in size, as pictured below.
Once the compressed Jiffy pellets have expanded in warm water, gently squeeze excess water from each pellet and you’re ready to go. Treat them the same as Rapid Rooters.
Germination Method 2: Plant marijuana seeds directly in growing medium
Sometimes nature’s way is the easiest way. In nature, marijuana seedlings would sprout in soil, and they would emerge as their taproots start growing down.
As a grower, you can also plant your seeds directly in your final growing medium. This works in all growing mediums, though some can be tougher than others.
One of the biggest benefits of planting your seed directly in the growing medium is you don’t have to worry about shocking your young seedling during transplant. Because your seed is already in its final resting place, your new seedling will immediately start adjusting to the environment. Every time you transplant a sprouted seed, it can cause stress as the young plant needs to readjust its new surroundings.
- Soil – Plant seeds a knuckle deep (0.5-1 inch OR 1.3 cm – 2.5 cm) in moist yet not soaking soil. Use a light or a heating pad to keep things warm. This is one of the easiest marijuana germination methods for beginners.
- Coco Coir or other soilless growing mediums – Plant in a similar way to soil
Germination Method 3: Germination Station
One option for growers is to use a tool which has been specifically designed to provide optimal germination conditions like this germination station with heat mat.
You can make a DIY germination station at home by putting a plastic dome over a plate on a heating pad.
There are benefits to the professionally made germination stations as they work very well and are pretty cheap to buy.
When growers start their cannabis seedlings in a germination station, the seeds are usually germinated in a starter seedling cube.
One of the advantages of starting seeds in starter cubes is your sprouted seeds can easily be transferred right to their next growing medium or container.
I recommend Rapid Rooters as these starter cubes work great for cannabis seeds and can be used in any growing medium including hydroponics, soil, or coco coir. Other starter cubes include Jiffy Peat Pellets, and Rockwool cubes.
Once your seed has sprouted, just make a little hole in your growing medium, and place the entire pellet inside. Make sure growing medium is also moist yet not soaking, like your pellet or cube. The roots will emerge from the bottom of the cube and burrow directly into your growing medium.
Germination Method 4: Soak Marijuana Seeds in Water Overnight
Another method to germinate marijuana seeds is to soak them overnight in slightly warm water, usually done in a glass drinking cup.
This method is especially effective for seeds which have extra hard shells, or seeds which are older (more than a few years old).
The warm overnight soaking can help “wake up” older seeds.
Most viable seeds will start out floating, and then eventually sink to the bottom of your glass after a few hours of soaking.
If soaked in a clear drinking glass, you will see when the little white tap root first breaks through the shell.
Some seeds take longer than others to sprout. Especially older seeds tend to need longer to pierce through their shell. However, if seeds are left soaking too long, and haven’t yet sprouted, they can drown.
Therefore, do not leave seeds soaking in water for more than 24-32 hours.
After 24 hours, I recommend putting any still-ungerminated seeds in a warm, moist place to finish germinating.
Germination Method 5: Paper Towel Method
One way to germinate seeds is to wet a paper towel and then fold your seeds in it, then leave the paper towel in a warm place.
Use cheap paper towels! For some reason, the really cheap paper towels work best because they’re so non-porous. Seeds and their roots lay on top without getting stuck to anything. This is important! The more expensive “cloth-like” paper towels (like Viva brand) aren’t good for germination because the roots actually grow into them instead of laying on top.
If you germinate your seeds in a paper towel, there is the risk of hurting the tap root (the little white root that grows out of your seeds) when moving the sprouted seeds so make sure you are careful when you’re checking to see if the seeds sprouted.
There is also the possibility of having the towel dry out which will kill your new seeds so I recommend putting your paper towel under an upside down bowl or between two paper (or regular) plates.
Check on germinating seeds once every 12 hours or so (don’t disturb them or their roots). You can plant any seeds which have sprouted right away, or leave them for another day or two, to let the others keep up.
How to Plant Your Germinated Cannabis Seeds
After you see that your cannabis seeds have sprouted, you should plant them right away.
You don’t want to touch the little white taproot with your fingers, so either carefully move the seeds, or use tweezers. If you do touch or break the root, the seedling may still survive, but any damage to the root will definitely stunt and slow down growth right in the beginning.
Plant seeds so that the white root faces downward, about a knuckle deep into your growing medium. The top of the seed should be just below the surface of your growing medium.
It can take anywhere from a couple of hours to a couple of days before you see the young seedling emerge from the soil or growing medium. If your marijuana seedling hasn’t sprouted from the soil within 10 days after being placed root-down, it probably isn’t going to make it Even with the best practices and the best seeds, you will occasionally lose a seed. Many times it has nothing to do with you!
First sign of taproots. These are ready to be planted!
Rapid Rooters are nice, but not necessary. You can use them before you transfer your seedlings to their final container. The Rapid Rooter should be cut open lengthwise if you plan on using them for germinated seeds. I use big scissors.
Gently place the germinated seed inside, root down. Place the seed close to the surface so it doesn’t have far to go.
Sometimes you’ll have a taproot that is curved or bent. You don’t want to try to straighten it out! Open the Rapid Rooter you split, and lay the germinated seed down gently. The seed and root will naturally lay on the flattest side. Slowly close the Rapid Rooter, and you’ll see that the bent parts of the root will end up in the “crack” of the Rapid Rooter from where you cut to split it open from the side.
After closing a Rapid Rooter, it’s hard to tell it’s been opened. The texture of Rapid Rooters causes the seeds to stay in place and not “fall down” further into the hole once you’ve got it closed.
Sometimes the shell can get stuck on the seedling, but it will often fall off on its own. If it seems really stuck, you can help the seedling by gently removing it.
Within the first week of germinating seeds, you will notice that some seeds germinate right away and others take a little bit longer. This can be caused by a lot of things, from the age of the seed (old seeds have worse germination rates and tend to take longer) to simple chance. The amount of time does not necessarily have anything to do with how healthy your plant will be in the long run.
Once your seeds are safely planted, you can turn on your grow light. The heat from the lamp improves germination rates, and the light can help your new cannabis seedlings open their first set of leaves. In fact, the first set of leaves will often stay yellow until they get light.
If you will be transplanting your seedlings again, avoid transplanting until they are well established and have a couple of sets of leaves (nodes). Some growers will plant seedlings in a growing medium in a solo cup or peat pot, so they can just cut away the cup for easy transplanting.
When you move seedlings around a lot, it stresses them out and potentially stunts their growth. Too much stress can even kill them. So try to plan from the beginning so that you move your seedlings around as little as possible. once they get bigger, they are a lot more hardy and can stand a lot more stress and movement.
Here are some pictures to give you an idea of the timeline to expect
Sprouted seeds planted in Hydrofarm pellets and placed on soil
If you want, you can put bottles on top to help retain extra humidity (like a cheap humidity dome).
It’s a steady 85 degrees F in there, no idea about the humidity in the bottles.
Marijuana seedlings under T5 Grow Light
Day 7 from seed
Your Cannabis Seedling’s First Few Weeks
During the first few weeks of a young marijuana plant’s life, you have to be careful.
Marijuana seedlings, especially seeds from some of the most potent strains, tend to be a bit delicate.
Seedlings definitely won’t be able to withstand full-strength grow lights or nutrients. They need to have a moist environment, but also can easily be drowned or overwatered.
If you’re planting in soil, start with a balanced potting soil that doesn’t contain extra nutrients. I recommend Happy Frog potting soil mix for young cannabis seedlings, but any plain potting mix from your local garden store will do. Never use Miracle-Gro soil or any soil that has “time-released” nutrients already mixed in. After your plants have grown a few sets of leaves, you can transfer them to a stronger potting mix that contains higher levels of nutrients like Fox Farms Ocean Forest soil, or you can start supplementing with cannabis soil nutrients. Don’t want to use nutrients? Learn how to mix up your own super soil so it has all the nutrients your cannabis plants will need!
If you’re planting in coco coir, a soilless medium, or hydroponics, only add cannabis nutrients at seedling strength, or 1/4 the regular strength, until your plants have grown a few sets of leaves. Then you can slowly start working your way up to full strength nutrient levels.
With young marijuana seedlings, less is more.
You’re trying to give young plants a very small dose of nutrients at first. However, even with young marijuana seedlings, the pH of your water and growing medium is important. Some growers get lucky and happen to have water with the right pH, but if you’re noticing deficiencies and problems with your seedlings, definitely take the time to understand about marijuana root pH and how it affects the plant’s overall health.
If you plan on eventually putting your marijuana seedlings under high intensity grow lights (such as HPS or MH grow lights), you may want to start them out with less intense fluorescent grow lights or compact fluorescent bulbs (CFLs). Or just keep your high intensity grow lights several feet away at first, and slowly move lights closer as your seedlings gets older
CFL bulbs (twisty/spiral bulbs as pictured to the right) are a great source of light for young marijuana seedlings
- CFLs provide the right types of light for seedlings
- CFLs are extremely cheap to buy
- CFLs are easy on your electric bill
- CFLs can be found almost anywhere, at your local hardware store, supermart, grocery store, or online
Keep CFLs or fluorescent lights about 6 inches away from your seedlings. Place your hand where the leaves are to make sure it doesn’t feel too hot. If it’s hot for your after 10 seconds, it’s too hot for your plants.
Once your seedlings have developed their first two sets of leaves, then you can move these lights as close as 2 inches away as long as the lights aren’t too hot.
Remember: If grow lights feels too hot to your hand after 10 seconds, they’re too hot for your marijuana seedlings
Make sure to keep a close eye on your seedlings to ensure they don’t grow too close to the grow lights and burn themselves. Seedlings can grow fast, and many growers have been surprised to find plants have actually grown into the light overnight.
If new seedlings are showing signs of stress, try moving the lights further away and see if that helps.
Once marijuana seedlings are about fourteen days old, they’re ready to start being treated as if they’re in the vegetative stage.
This Timeline Will Help Show You What to Expect
Two round cotyledon leaves, then two “real” (serrated) single-finger cannabis leaves
Next, the single-finger leaves expand, and the next set is usually 3-finger leaves
Next, the cannabis plant will start making 5-finger leaves
Finally, most cannabis plants stop at 7-finger leaves
If you look closely at the above plant, you can see that some of the newer leaves on this plant actually have 9 fingers. It is normal for there to be some variation between leaves – some plants will grow leaves with 11 or even 13 fingers. But the above guide will give you a general idea of what to expect.
Once your cannabis seedling is about fourteen days old, it’s ready to start being treated as if in the vegetative stage.
Make sure you learn about plant training techniques to make the most of your time in the vegetative stage!
Wait! My seed is growing upside down with the roots up; what do I do?
As long as the roots of a cannabis seedling are able to grow down, they will. Roots never grow upward on their own. Seedlings can sense the difference between up and down. Roots always try to grow down. Roots never grow upwards.
So how come sometimes it looks like a cannabis plant is growing with its roots pointing up?
When the seed end is still bent down, all you see is a U-shaped stem/root
Cannabis seeds can look a bit different when germinating. When in doubt, always wait a few days to see if leaves appear before you try to interfere.
Sometimes the stem of a brand new cannabis seedling can look like the roots growing out the top. But if you wait and watch, you’ll see that it’s all part of the plan. Hope these pics help someone!
Sometimes you’ll see what appears to be roots emerging from your cannabis seed, but this is actually the stem. The stem pushes the seed and leaves up, and the main taproot is currently burrowing down to support the seedling
As the seedling emerges you’ll be able to see the leaves (sometimes it will still have the seed stuck on the first leaves, like in the picture above).
The cotyledons (first, round leaves) unfurl, and then the regular cannabis leaves between to grow. Here’s another view of that same seedling from above. Even though it may have looked a bit weird at first, this seedling is completely normal and will grow just fine from now on.
What Size Pot Should I Use?
When growing cannabis plants in a container, you have to choose the size of your pot.
A general guide is to have about 2 gallons per 12″ of height. This isn’t perfect since plants often grow differently, but this is a good rule of thumb.
When in doubt, get a bigger final container size as opposed to a smaller one. Plants that get rootbound from being in a too-small container will grow more slowly and be prone to problems. It’s not good to transfer plants during the flowering/budding stage, so you want to have your cannabis plants in their final container at least 2 weeks before the beginning of flowering/budding. How do I get my cannabis plants to start flowering?
Final Container for Desired Plant Size – General guide
12″ ~ 2-3 gallon container
24″ ~ 3-5 gallon container
36″ ~ 5-7 gallon container
48″ ~ 6-10 gallon container
60″ ~ 8-10+ gallon container
But what size pot should you use for your seedlings?
For fastest growth rates, it’s better to plant young seedlings or clones in a very small container, like a disposable plastic solo cup.
For new seedlings and clones, use a small container if possible
The reason you want to start with a small container is that your plant’s young roots thrive on oxygen. Cannabis plant roots “breathe” oxygen, just like we breathe air, and it’s important that young cannabis roots get plenty of oxygen so the plant can grow as fast as possible.
However, young plant roots do not drink much water yet. When you water seedlings or clones in a very big container, they will use up all the oxygen quickly, and the large size of the container will prevent the growing medium from drying out.
A big plant will drink up all the water quickly, but with seedlings, you’re basically waiting for the growing medium to dry out by itself. While you’re waiting for the container to dry out, your cannabis roots are sitting in a wet environment and not getting much oxygen, slowing down their growth rates.
Poke holes in the bottom of your cup so water can drain out easily!
By planting young seeds in a small container with holes in the bottom, the growing medium will dry out much more quickly, allowing you to water more often. The young cannabis will get plenty of oxygen and water.
Alternative to Solo Cup: Start plants in seedling cube
If you don’t want to have to transplant your young plants, you can start them in a seedling plug or cube and wait until you start seeing roots come out the bottom. At that point, they will be ready to be transferred to a larger container.
What happens if I plant seeds or clones in a big container?
Your cannabis seedlings and clones will definitely survive in a bigger container; they just won’t grow as fast for the first few days or weeks because they aren’t getting as much oxygen.
With a bigger container, you will need to wait longer between waterings, and during that time your plant roots will be getting reduced oxygen.
If you’ve planted your young plant in a large container, try to give only a little bit of water at a time (enough to wet the area around the seedling roots) until the plant is growing vigorously. Once the plant has grown a few sets of leaves, you should start watering cannabis normally so that water drains out the bottom.
One of the advantages of starting young plants in a big container is you won’t have to transfer them to bigger containers as they get older.
If you would like to take advantage of faster vegetative growth from transplanting, view the Complete Cannabis Transplant Guide (with pics!)