How To Grow Cannabis: How to Germinate Weed Seeds
Let’s say you’ve got some cannabis seeds that you found on the side of the road or were maybe gifted from a friend in the same state. Nice job! Below, we will break down a little bit more on how to germinate weed seeds using a paper towel.
Germination is relatively easy when you have all the right gear. Again, I’m growing outdoors in soil and was gifted three autoflower strains, so everything below is specific to those parameters.
If you’re growing outdoors and want to maximize your time, plan to start germinating and transplanting a few weeks before the last spring frost date in your region (depending on your climate). This way, by the time the weather is warm enough and the risk of frost is gone, you’ll be ready to move your seedling outside.
>> Buy some top-tier cannabis seeds at Homegrown Cannabis Co.
Disclaimers: NOT FOR SALE OR TRADE. The following post features content about cannabis cultivation and germination and other related material that is illegal under federal law as well as under state law in certain states. This content has been produced by Thunderbird Disco—located in the Commonwealth of Virginia—for educational and entertainment purposes only. All cultivation described below was completed in accordance with Virginia law as authorized in § 4.1-1101 Home cultivation of marijuana for personal use; penalties.
If you missed Part 1 of this series, feel free to check it out. For purely educational purposes, I highly recommend Homegrown Cannabis Co. seed bank, which has terrific video content and information on seeds, as well as I Love Growing Marijuana, which has an excellent 70-page “Grow Bible” eBook for beginners and plenty of information on autoflower seeds.
This post contains affiliate codes or links that are no additional cost to you, and I may earn a small commission when a purchase is made.
This video is good starting point for how to germinate weed seeds. If you’re growing autoflowers, don’t follow Part #7 of this series closely (it’s specific to photoperiod plants).
This won’t all make sense yet, but here’s a handy dandy week-by-week outdoor autoflower cannabis growing cheat sheet for all your watering, nutrient and general maintenance needs
MATERIALS You Need
White paper towels (no dyes or patterns)
Glass measuring cup (something with a spout)
Purified water
Glasses
Dinner plates
Labeling tape
TIME TO GERMINATE: 2-3 days
WEEK ZERO: GERMINATION
Step 1: Soak Your Seeds
Pour purified water into a measuring cup and add just a drop of liquid seaweed. Stir. If you’re growing multiple strains, don’t mix all the seeds together in one vessel! Label different glasses with the different strain names and pour some seaweed water into each glass. Place your seeds in this water and let soak for about 24-48 hours in a warm, dry, dark place. Moisture and humidity help start the germination process.
Step 2: Second Soak
Add another few drops of liquid seaweed to some purified water. You’re going to make this little wet paper towel sandwich with your seeds in the middle (follow this video). Stack 2-3 paper towel squares, fold in the corners to make into a diamond, place it on a dinner plate and then wet it down with seaweed water. Gently spread your soaked seeds onto this paper towel (again, keep the strains separate, and transfer the label from the glasses to the dinner plate). Now add another stack of 2-3 folded paper towels on top, and again wet it down. You want this stack to be wet but not soaking (no standing water on the plate). Plan to leave this for another 24-48 hours.
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Step 3: Keep Moist
Don’t let the paper towels totally dry out — again, the humidity and moisture will help germination. Check every 8-12 hours or so and add more seaweed water as needed.
Step 4: Check for Taproots
After 48 hours, very carefully peel back the paper towel and check to see if there’s a taproot coming out of each seed. The root is likely a bit stuck to the paper towel, so go very slow and make sure you don’t damage this sprout while you’re peeling off the paper towel. If you see taproots, go on to the next phase. If not, let the baby seedlings sit in the moist towel for another day or two.
Once you have your taproot showing…
WEEK ONE: SEEDLING STAGE
MATERIALS
3- or 5-gallon Grow Bags (I used Opulent Systems 3-gallon)
Seed Starting Mix (I used Fox Farm Light Warrior)
Pre-Amended Potting Soil (I used Fox Farm Ocean Forest)
pH Adjusters (General Hyroponics pH Up/Down, or distilled white vinegar)
Plastic Wrap
Binder clips
Grow Lights (could be a basic LED grow light, a midrange LED grow light, or a more advanced grow light system (use coupon code “THUNDERBIRD” for 15% off)
Hydroton clay pebbles (optional)
Seedling Heat Mat and Thermometer (optional)
IMPORTANT: You’ll find some videos online (like this one from Homegrown) that recommend first planting germinated seeds in Solo cups and then transplanting them to larger pots or grow bags … but this is only for photoperiod plants. I accidentally did this with my seeds and the transplant process either killed or at least stunted my autoflower plants’ seedlings, which aren’t as robust and don’t have as much time to recover from the stress of transplanting. Plus, it’s an annoying extra step. Having tried it both ways, I highly recommend planting germinated autoflower seeds directly into the pot or grow bag that they’ll live in forever. You can see the side-by-side comparison below.
>> Buy some top-tier cannabis seeds at Homegrown Cannabis Co.
Step 1: Prepare Grow Bags
To get started, add a 2-inch layer of Hydroton to the bottom of your grow bags (optional, but helps strike a balance between good drainage and moisture retention). Fill your bags most of the way with Fox Farm Ocean Forest super soil (a favorite among growers you’ll see abbreviated as “FFOF”).
Don’t press down or pack the soil in; keep it light and fluffy. One great feature of this soil is that it is resistant to damping off, mold, and fungus, which can cause disease and other issues throughout plant development.
Step 2: Add Seed Starting Mix
Scoop out a small bowl’s worth of FFOF and in that center hole add in some of the Light Warrior seed starter mix. This stuff is a little lighter and has fewer nutrients, so it won’t “burn” the tender seedling. But as the taproot grows and the roots begin to establish and stretch out, they’ll reach the “hotter” FFOF mix once they’re strong enough to handle it.
Step 3: Prepare pH-Adjusted Water
You can take your chances with tap water or distilled water, but it may not be in the ideal pH range of 6.0 - 7.0 that autoflower cannabis plants require. Proper soil pH is what determines how well your plants can uptake nutrients, and anything too far out of the optimum range will be like they’re drinking through a pinched straw.
Use your properly calibrated pH meter to test your tap water. Mine was in the 7.5 range, so I needed to adjust down. You can use professional pH products but I just added a little distilled white vinegar to make the water more acidic and bring the pH down. You only need a tiny bit, like 1-2 ml per gallon of water, to shift the pH, so go slow and see what it takes to get close to that sweet spot of pH 6.5. You’ll be using pH-adjusted water throughout the grow process, so might as well start practicing this step (don’t make the mistake I did, thinking this was a complicated and unnecessary step; bad pH can lead to all kinds of problems for your plant).
>> Buy some top-tier cannabis seeds at Homegrown Cannabis Co.
Step 4: Moisten Soil in Grow Bags BEFORE Adding Seeds
Saturate your grow bags with this pH-adjusted water to moisten the grow medium. Do this before adding the seeds, or else you risk disturbing the seed or having it float away.
Step 5: Add Germinated Seeds
Gingerly place one germinated seed in the center of each wet grow bag (the area with the Light Warrior Seed Starting Mix), taproot facing down. Just barely cover it with soil. Make sure you continue to track which seeds/strains are in which bags, adding plant labels to the bags or to the soil. Place plastic wrap over the top of the grow bag and secure with clips. Poke a couple of holes in it to create a nice warm terrarium kinda thing.
Step 6: Add Light
Place these grow bags under the LED grow lights turned on 24 hrs/day, with the soil about 8-12 inches away from the bulb. After about 48 hours, check to see if the seeds have sprouted. Once you see little green leaves poking out from the soil, remove the plastic wrap from the bags. Seedlings crave warmth at this stage, so if the bags are in a cooler spot consider using something like this Seedling Heat Mat and Thermometer setup to warm it up a bit.
Step 7: Leave Them Alone!
Seedlings need VERY little at this stage other than 24-hr light. If you think you should water them, probably don’t! If you think you should feed them with nutrients, probably don’t! The magic is in the seed itself and the existing wet nutrient-rich soil in the bag will be sufficient for 2-3 days. Only give it a very little bit of pH-adjusted water every few days, after the soil feels dry. I killed or stunted a bunch of plants by watering them too much.
Okay, then what?
Click Here—> HOW TO GROW CANNABIS #3: VEGETATIVE STAGE
How to Germinate Weed Seeds: FAQs
How long should you let a weed seed germinate?
Once you get started with the germination process, expect to wait between 2 to 4 days before the seeds are germinated.
What is the best way to germinate seeds?
I recommend using the paper towel method — this is usually the easiest and least stressful way to get the taproots out of your seeds.
Does weed germinate in light or dark?
Cannabis seeds germinate best in a moist, cool, and dark place. Once they develop their first cotyledon (leaf) they will then need light to grow.
Do you have to soak weed seeds in water?
It’s best not to soak your seeds in water, but rather have them in a moist place such as the process described above.
Do weed seeds need to be warm to germinate?
Yes, cannabis seeds will need some warmth to germinate properly. The ideal range is usually between 70°F to 80°F.
