Grow Guide: How to Start Cannabis from Seed
Starting cannabis from seed is an affordable and fulfilling way to start growing. It all starts with germinating cannabis seeds, followed by creating the ideal warm, humid environment for seedling growth.
Giving your seeds (and then the seedings) the best support from the very start, you’ll set yourself up for success come harvest. Here are the basics to growing cannabis from seeds.
Where to Find Cannabis Seeds
At this point, there are hundreds of different online options for sourcing cannabis seeds . If you are growing indoors, the world is your oyster, as many websites are willing to ship nationally (or even internationally). Plus, if you master the indoor environment, you can recreate perfect conditions for even the most demanding of strains.
For those growing outdoors, try to locate a local breeder who also cultivates outside. These cultivars will be adapted to your unique climate and will likely produce better results.
No idea where to start? Seed Finder is an excellent resource for sourcing specific genetics and breeders in your area. But this is just one place among many in today’s weed-friendly world.
How to Germinate Cannabis Seeds
What You’ll Need:
- Cannabis seeds
- Paper towel
- Plate or tray
- Ziplock bag
- Heating mat (optional)
The first step to growing cannabis from seed is learning how to germinate them. Place cannabis seeds on a sheet of paper towel, laid on top of a tray. Dampen the towel with water so it’s wet but not soaking.
Fold the towel in half to cover the seeds, and enclose it inside a Ziploc bag. Place the entire tray on a heating mat, the top of a fridge or other warm area of your house. Cannabis seeds germinate between 71 to 77°F (22–25°C).
Check back every day for signs of life. If your seeds are viable, they should sprout within a week. If you are still waiting for a few to emerge after a week, toss those and begin again. If no seeds have sprouted, your seeds are no longer viable.
Ed Rosenthal recommends soaking seeds for 12 hours before germination. His formula uses water, a cannabis rooting solution and hydrogen peroxide.
This solution is a good option for commercial and large scale growers, as it reduces the risk of fungal infection and encourages rapid sprouting. Compost tea is another excellent option for a natural alternative.
Ideal Conditions for Cannabis Seeds and Seedlings
What You’ll Need:
- Germinated Cannabis Seeds
- Potting Mix (or Root Riot Plant Cubes )
- Propagation Tray with Dome
Once germinated, you must carefully move these tiny seeds into the soil or soilless growing medium like Root Riot Plant Cubes. When you start cannabis from seed, the aim is a warm and relatively humid environment.
Starting Cannabis With Soil
If using soil, choose an organic potting mix suitable for seeds and starts. Water soil mixture before use, and fill potting containers that have a drainage hole. Avoid pellets that are commonly sold at garden centers, as they don’t retain moisture well, and it’s challenging for cannabis roots to break free of the netting.
Using a popsicle stick, tweezers or a toothpick, lower the germinated seed into a premade hole roughly two the three times the height of the seed. As you gently fill in the hole, be careful not to damage the sprout.
Starting Cannabis for Hydroponics
For hydroponics, you’ll want to use Rockwool cubes or Root Riot Plant Cubes. These come pre-cut into perfect starter plugs, often with a hole in the middle for the seed.
Before use, soak the cubes in water and rooting solution until they are wet but not dripping. Gently lower the germinated seed into the hole using a popsicle stick, tweezers or a toothpick. Be extremely careful not to damage the early sprout.
Whatever option you choose, keep the seedlings at a consistent temperature: 68 to 77°F (20 to 25°C). Depending on where you live, a heating mat may be necessary. Use a propagation tray with a clear dome to trap the humidity in, but open up once a day to encourage a bit of airflow.
Lighting Requirements for Cannabis Seedlings (& How to Eliminate Stretch)
Seedlings and starts require 16 hours of light a day and eight hours of dark. You can even bump this up to 24 hours a day, and the seedlings will continue to eat it up.
What kind of grow light do you need for this early stage of development? Not the same capacity you’ll need for veg and bloom. Higher wattage types of HID lights (Metal Halide and High-Pressure Sodium) are far too powerful for sensitive seedlings.
Most growers use a simple LED grow light or a CFL fixture. Ed Rosenthal recommends 40 to 60 watts per square foot.
While these may not be entirely enough for veg and bloom, they produce enough light for seedlings without the added heat. This means you can place the lights close to the tops of the seedlings.
Place lights as close as possible to the tops of the starts, without raising the temperature over 77°F. You want seedlings to get enough light without burning them.
The goal is to avoid early stretching in your small cannabis seedlings. Healthy seedlings are short and wide, not tall and skinny. Stretching is when the sprout reaches tall for the light without putting out leaves.
Typically, under outdoor conditions, plants remain short for the first few weeks as they focus energy on building structure and root development. Stretching inside demonstrates the seedling is not getting enough light. The light source is either not intense enough or too far away.
When to Transplant Cannabis Seedlings
The primary goal for starting cannabis seeds in small pots is to encourage healthy and strong root development. Once the seedling has three to four sets of leaves, begin checking root development. This will likely be three or more weeks after germination.
Another telltale sign it’s time to transplant is when you notice roots begin to creep out from the drainage holes. If working with Rockwool, a key indicator it’s time to transplant is when the roots begin to outgrow the cube. A plant’s growth trajectory slows down if it is root-bound. If the roots have consumed the available space, it’s time to move up a size.
Cannabis Seedlings From Germination to Transplanting
Starting cannabis from seed gives growers access to a much larger genetic pool than what you can find locally from a clone supplier. Plus, if you’ve got the time to invest, it’s a much more affordable way to grow cannabis. Finally, if you are already set up with a veg and bloom room, you have everything you need to get started from seed.
How and when to transplant cannabis plants
Transplanting is the process of “re-homing” a cannabis plant, or moving a plant into a bigger pot with more soil as it grows bigger.
Growers typically start off the cannabis growing process by planting many seeds in small pots because they don’t know if all of them will sprout—or germinate—and they don’t know if all of them will be female.
Only female cannabis plants produce buds, so if you start growing from regular seeds, you will have to sex them out and discard the males.
Why is transplanting marijuana plants important?
Transplanting gives a marijuana plant’s root system more space to spread out, allowing the plant to grow healthy and strong and to flourish.
When roots become cramped and can’t spread out they can get tangled and become “rootbound”—this will effective choke the plant, leading to a stunted, sickly plant, and can even kill it. A healthy root system will lead to a healthy weed plant.
A plant’s container will determine how much the roots can stretch out, and therefore how big your plant will get. A container that’s too small will stunt it.
You don’t want to plant a seed in a giant pot because you could potentially waste soil if the seed doesn’t make it. Also, if growing weed outdoors, it’s hard to plan out a garden and where to put your seeds in the ground if some seeds don’t make it.
Most weed growers start seeds in small 4-inch or 1-gallon pots when germinating.
For the seeds that do make it, they will need bigger homes after several weeks of growing and will need to be transplanted either into a bigger pot or directly into the ground.
When planting into the ground, make sure not to crowd your plants so their roots don’t run into each other.
The symptoms of a rootbound plant include:
- Flimsy new growth
- Stunted flower production
- Stem discoloration (reddening)
- Nutrient sensitivity
A rootbound plant may also appear under-watered. If a plant requires watering more than once a day, it may need to get transplanted.
When to transplant marijuana
Check out Johanna’s full video series on how to grow weed on Leafly’s YouTube .
Most marijuana plants go through 1-2 transplants during their life but could have more. As an example, transplanting can happen from:
- First container (1-gallon) to second container (2-gallon): 4-8 weeks after seed germination
- Second container (2-gallon) to third container (5-gallon): transplant 8-12 weeks later, or 2 weeks before flowering
Some growers may only transplant once: using the example above, from a 1-gallon to a 5-gallon container, skipping the 2-gallon. And depending on how big you want your weed plants to get, you may transplant into bigger pots than what’s listed above.
The same goes for transplanting outside, in the ground—you can go straight from the first pot into the ground, but it depends on when you transplant and your local climate and weather.
Here are some indicators that your cannabis is ready for a new container.
Number of leaves
Young plants sowed in small containers are usually ready to be transplanted after they’ve sprouted 4-5 sets of leaves, but keep in mind this may vary from strain to strain.
Check the drainage holes at the bottom of the container—a plant should have a healthy and visibly white root system. If roots are growing out of the holes, it’s time to transplant.
Any discoloration or darkening may indicate the plant has become rootbound and a transplant should take place immediately.
End of vegetative stage
A weed plant should be in its final pot or in the ground with plenty of room for its roots before it enters the flowering stage. During flowering, a plant will increase in both size and volume, as the plant itself continues to grow and as buds develop. It will require a substantial amount of space for root development.
How much space does a marijuana plant need?
|Plant height (inches)||Pot size|
|0-6″||4-inch (16 oz.)|
When transplanting cannabis, give the plant at least double the space of its previous container. This reduces the number of times you need to transplant and minimizes the risk of transplant shock, which may occur when a plant experiences extreme stress from root disturbance.
For example, you could go from a 1-gallon to a 2-gallon to a 5-gallon, or from a 2-gallon to a 5-gallon to a 10-gallon.
Medium-sized indoor cannabis plants tend to be fine in 5-gallon containers as a finishing pot. Large outdoor plants may require much bigger containers to reach their behemoth potential, sometimes up to 10- or 20-gallon pots.
When in doubt, always opt for slightly more space than needed. A plant tends to require 2 gallons of soil for every 12 inches of growth it achieves during the vegetative stage. Knowing the potential height of the strain you’re growing is helpful.
Why not start in the largest pot for your marijuana plant?
Growers typically transplant weed plants 1-3 times, moving plants to bigger pots gradually as they get bigger.
If a plant is put in too big of a pot, the roots won’t stretch out that much and won’t soak up as much water. This can cause water to sit in the pot for a long time, waterlogging the plant and leading to root rot.
You can transplant into the largest pot for your weed plant to avoid multiple transplants, but be careful not to water all of the soil—only water around the stalk of the plant where the young roots are.
How to transplant marijuana
Check out Johanna’s full video series on how to grow weed on Leafly’s YouTube .
The process of transplanting weed does not come without risk. Transplant shock can be incredibly detrimental to the growth and development of a cannabis plant, and can even kill it. However, through proper execution, the process of transplanting will benefit the plant and lead to stronger root development and healthier flower production.
First transplant of a cannabis plant
Young cannabis plants should start in a 4-inch or 1-gallon pot. This starting pot should be adequate for a few weeks before transplanting is needed.
Again, the first transplanting should occur after the seedling has sprouted its 4th or 5th set of leaves. To transplant:
- Wash your hands and/or wear gloves to prevent contamination of the delicate roots, and keep the surroundings as sanitary as possible.
- Give the plant a light sprinkling of water to help minimize shock; don’t drench it, as the soil will be difficult to work with.
- Fill the receiving pot with soil, allowing enough space for the new plant.
- Avoid overpacking the soil during and after transplanting—this can compromise drainage and damage the root system.
- Do not disturb or damage the roots when transplanting; the first transplanting poses the greatest risk for shock, which can occur from root damage and agitation.
- Avoid intense light when transplanting; this will help prevent transplant shock as well.
- Fully water in the plant once it’s in its new home.
Additional transplanting of cannabis plants
You may need to transplant your weed plant a second or third time to maximize its growing potential. Always monitor plants for symptoms of distress or overcrowded roots.
To do so, follow the steps above, and make sure the new container is at least twice as big as the old one, if not bigger.
The finishing container is the final home of a plant until it’s harvested. This will be the largest container for a plant, and you always want to transplant into this pot 1-2 weeks before the flowering stage—you don’t want to disturb a plant while it’s flowering.
Keep in mind that large plants may require stakes or other support to avoid structural damage after transplanting.
How to Plant Cannabis Seeds Indoors
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Growing cannabis at home can be a fun project and a nice way to have your own cannabis plants on hand. You may want to grow cannabis indoors due to inclement weather in your area or due to a lack of green space in your yard. Start by germinating the seeds. Then, plant the seeds in soil or in a starter cube. Once the seeds have been planted, care for them properly so they grow and thrive.
- After 12 hours, place the viable seeds on a towel.
Wet one paper towel and put it on a plate. Paper towels are thick enough to retain the moisture needed to help the seeds germinate. Place one paper towel under running water until it is wet to the touch, but not dripping wet. Use a ceramic dish or plate, as it will be strong enough to hold the towels and the seeds. The paper towel should cover the dish or plate.  X Research source
- If you do not have enough space on one plate for all your seeds, soak two more paper towels and put the remainder on a new plate covered in a wet paper towel.
Wet other paper towel and place it over the seeds. Make sure the wet towel makes contact with the seeds.  X Research source
- You can try using a heat lamp near the seeds to keep them warm. Do not warm the seeds up too much, as you do not want your heat source to dry out the paper towels.
- If the seeds become too dry, they could die and never germinate.
- Be very careful with the seeds as they open. Avoid prodding, pulling, or touching the seeds, as you do not want to damage the roots.
- Any seeds that have not opened and grown roots within a few days should be discarded, as they are not viable.
- As an alternative to soil, you can use starter cubes from your local nursery or online. Starter cubes are pre-cut growing pods made of composted bark. They contain a hole where you can place the cannabis seeds and grow them in good conditions. Basic starter cubes are inexpensive and easy to use.  X Research source
- If you make planting holes that are too shallow, the seed’s roots will not have enough soil to grow well. If you make the planting holes too deep, the seed will have a difficult time sprouting.
- Do not pull or tug at the seeds when you pick them up with tweezers. If they are stuck to the paper towel, wet the towel with water to make the seeds easier to pick up.
- Do not press hard on the seeds when you cover them, as this can disturb their growth.
- If you are using starter cubes, pinch the top of the holes in the cubes closed.
- Maintain a growing temperature of 75 to 85 °F (24 to 29 °C) for the plants so they thrive.
- Stick to a regular watering schedule so the plants get enough moisture. You can plan to spray the plants in the morning and then again at night so they get the water they need.
- Grow lights range from $200 to $1,200 USD depending on the size and model.
- You can get cool white grow lights at your local hardware store or online.
Avoid touching or handling the seeds as they grow. Touching or handling the seeds can damage them and stunt their growth. With the right growing conditions and care, your seeds should sprout and poke out of the soil within five to ten days.  X Research source
More than 12 hours of light a day for about 4-6 weeks as the plant matures will be enough. Once the plant is a decent size, you may induce flowering. Switch the plant to a timer of EXACTLY 12 hours of strong light (the more sunlight the plant gets, the more energy it can devote to flowering).
Yes, it is bad for the plant to have water constantly sitting at the bottom of the pot. It could make the roots rot over time.
You can actually find LED lamps made for growing plants online. If you don’t want to bother with that, you can just get a purple light to grow them under. There are many articles online talking about the effects of colored lights on plants.
If you plan on growing short, fat plants, they should be at least 6′ apart. You don’t want the plants rubbing on each other or shading the other plants. You will also want to select a spot to ensure all plants will receive maximum sunlight.
You can start as soon as you see two little leaves budding. During that time, make sure to use distilled water when watering them.
Cannabis thrives in a comfortable room temperature when grown indoors, or a little warmer – not too dry, not too humid. If it feels too hot or too cold for you, it’s probably too hot or too cold for your cannabis plants.
You can’t. You can try keeping it by a window, but you still won’t have much success. Lights aren’t that expensive, look on Amazon.
Yes, rain water is fine for any plant. The use of distilled water is to keep from adding tap water contaminants.
Keeping the plant from “stretching” is simple. Place the lights closer to the top of the plants. There are good video examples on YouTube showing two seeds started at the same time and placed under lights at different heights. The plant with inadequate lighting actually “reaches” for the light, growing tall and thin with longer internodal gaps. The seedling with closer light grows short and squat, with less stem between leaves (internodal distance), which means a better frame and plant structure for supporting the massive buds that you want to grow. As the plant grows, raise the lights with it. (Most folks suggest somewhere in the 16-30 inch range from source to canopy.)
The cultivation of cannabis is considered illegal in many jurisdictions. Make sure it is legal to grow cannabis in your area.
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About This Article
This article was co-authored by wikiHow Staff. Our trained team of editors and researchers validate articles for accuracy and comprehensiveness. wikiHow’s Content Management Team carefully monitors the work from our editorial staff to ensure that each article is backed by trusted research and meets our high quality standards. This article has been viewed 1,330,133 times.
To plant cannabis seeds indoors, first soak the seeds in lukewarm tap water for 12 hours. Discard any seeds that float to the top. Then, place the seeds on a damp paper towel on a plate with 1 inch (2.5 cm) of space between each seed. Cover the seeds with another damp paper towel. Keep the seeds in a spot that remains between 70-80°F (21-27°C), and spray the paper towels with water whenever they start to dry out. The seeds will sprout in 2-3 days. When they do, fill pots or a growing tray 3/4 of the way with loose potting soil that has a pH between 5.8 and 6.3. Press the soil down lightly, leaving some air in it. Then, use a pencil to poke 1 inch (2.5 cm) holes in the soil. Place the sprouted seeds vertically in the holes and fill the holes with potting soil. Water the soil thoroughly and place the pots or tray in a spot that’s always 75°F (24°C) or warmer. Set up a grow light over the seeds and leave it on at all times. Water the seeds every day so the soil doesn’t dry out. The seedlings will emerge in 2-4 weeks. To learn how to use cool white grow lights to help your cannabis seeds grow, keep reading!
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