In this tutorial, we walk you through everything you need to know and do to grow cannabis seedlings in coco coir: pots, light, fertilizers, watering & more One of the most tricky things about growing your own cannabis is how to correctly germinate cannabis seeds. Here's an easy guide on how to go about that. A step-by-step guide for successful cannabis germination grounded in science. Reviews strategies for germinating cannabis seeds and offers tips for success.
How To Grow Cannabis Seedlings in Coco Coir
The seedling stage is one of the most sensitive periods of a plant’s life. If managed well, seedlings develop into strong young plants that go on to be solid producers. However, if managed poorly, the plant can become stunted and never live up to its potential. Caring for seedlings in coco coir can be tricky, but we have you covered. In this tutorial, we walk you through everything you need to know and do to grow cannabis seedlings in coco coir. We cover how to prepare coco for seedlings, the best containers for seedlings in coco, relative humidity for cannabis seedlings, temperature for cannabis seedlings, light for cannabis seedlings, fertilizers for cannabis seedlings, how to water seedlings in coco coir, and how to treat seedlings with calcium deficiency.
This tutorial covers the roughly two-week period of the seedling stage. The seedling stage starts when the cotyledons (first round leaves) open, usually around 3-4 days after the seed gets wet. The seedling stage runs until the plant has three true nodes (sets of serrated leaves). Hence, this tutorial covers roughly days 3-15 from seed. For those crucial first 3 days, be sure to see our tutorial “Germinating Cannabis Seeds – a Step-by-Step Guide”.
As the plants start maturing during the seedling stage, it is time to work your way through a transplant strategy. We recommend that you always use a transplant regime and never start seedlings in final containers. For simple instructions and our explanation, be sure to see our tutorial, “Transplanting Cannabis Plants: Why, When & How”.
You will eventually get to final containers, so be sure to read our recommendations in “Pot Size and Type: The Best Containers for Cannabis in Coco” (Coming Soon). The end of the seedling stage is also when you should think about training your plants, so be sure to read our article, “Why You Should Train Cannabis Plants” and see our training tutorials.
How to Grow Cannabis Seedlings in Coco Coir
Coco Coir, CalMag and Seedlings
Before you use coco, it should be properly rinsed, buffered and mixed with perlite. Be sure to see our video and tutorial for “How to Prepare and Buffer Coco Coir”. The buffering process is crucial to prepare the coco for plants, and especially seedlings.
As I explain in the article, “Why You Need Cal/Mag in Coco”, the coco itself has cation exchange sites that need to be filled with calcium or magnesium. Buffering the coco allows you to satisfy the majority of the cation exchange sites. However, during the grow, more cation exchange sites are continuously exposed, which require additional CalMag. The coco will take its share of the calcium and magnesium before the plant has a chance, so if you do not provide enough, the plant will suffer.
Calcium and magnesium deficiencies are common problems with plants grown in coco. It is especially difficult to deal with CalMag problems during the seedling stage. This is because the coco is taking the Ca and Mg from the nutrient solution. However, you cannot simply increase the dose. You are limited in the amount of CalMag that you can provide to seedlings because they cannot tolerate a solution with high Electrical Conductivity (EC). CalMag has a strong impact on EC so when seedlings do suffer Ca or Mg deficiencies, they can be tough to correct. If you do encounter problems with Ca or Mg deficiency during the seedling stage, we have suggestions for you below. However, it is best to avoid the problems in the first place by properly preparing your coco.
How to Prepare Coco for Seedlings
Buffering with a strong dose of CalMag prior to using the coco allows you to provide relatively little CalMag during the seedling stage of the grow. However, buffering solutions themselves have a high EC, and seedlings could be burned if they are placed in coco fresh from the buffering process. Therefore, it is important to reduce the residual EC in the coco before transplanting the seedlings.
When I begin a grow, I prepare and buffer enough coco for the final containers. I keep the bulk of the coco/perlite moist with CalMag Water in fabric pots until I need it. When it comes time to place seedlings into coco, I fill the seedling container with coco/perlite and then flush it by pouring pure water with a pH of 6.5 though the container until the run-off is less than EC 100 (0.1). This flush is important because otherwise the residual high EC from the buffering process could burn your sensitive seedlings.
Containers for Seedlings in Coco
We recommend growing sprouts first in a Rapid Rooter or Jiffy Pellet before transferring to coco. These peat-based media provide a more stable buffer for germinating seeds and sprouts. Be sure to see our tutorial, “Germinating Cannabis Seeds – a Step-by-Step Guide”.
When the root of the sprout grows through the Rapid Rooter or Jiffy Pellet, the little plant should be transplanted into the first container, where it will live out its seedling days. We advise strongly against placing small plants into large final containers. As I explain in our article, “Transplanting Cannabis Plants: Why, When & How”, there are significant benefits to starting plants in small containers.
When the root emerges, we recommend placing the plants into either fabric seedling bags or solo cups with prepared coco. The seedling bags create an ideal environment for young roots, however the solo cups are somewhat easier to transplant out of at the end of the seedling stage. If you use solo cups, be sure to cut numerous holes in the bottom of the cup to allow drainage.
Transplanting out of seedling containers can be tricky whether you use fabric seedling bags or plastic solo cups. For complete instructions and photos of the process be sure to see “Transplanting Cannabis Plants: Why, When & How”.
How To Germinate Cannabis Seeds
Growing your own weed is fairly easy, as explained in our article ‘All You Need For Growing Weed At Home‘. The hardest part for some growers though, is germinating their newly bought cannabis seeds. After all, the vulnerable seedlings are easily damaged. However, making sure your cannabis seeds survive germination is essential for a successful grow. In this blog, we highlight three tested methods that let anyone germinate cannabis seeds with minimal effort.
How To Germinate Cannabis Seeds, Step 1: Get Good Genetics
We cannot stress this enough. If you want good results, you are going to need good materials to start with. In case of growing cannabis, the first thing on that list are good cannabis seeds, of course. Besides high quality cannabis seeds all you need is some water, a warm environment (between 20-25 degrees Celsius) and – lack of – light to start germinating your future cannabis plants.
Even though living weed plants love (and need) a lot of light, germinating cannabis seeds thrive better in a dark environment. And just like there are different methods of growing your own cannabis, there’s also a choice in how to make your seeds sprout.
Want good cannabis? Get good seeds!
Germination is actually a process where you activate a dry seed that is in a ‘sleeping state’. By adding water to the seed, a small root that is inside the seed-shell will want to come out in search for more water. This will make it develop into a big taproot that’ll serve as an anchor for the plant and from which more roots will sprout. Read more about root-development in this article: ‘Clones vs. Seeds: What Grows The Best Cannabis?‘
Germinate Cannabis Seeds In Water
The easiest way to germinate your cannabis seeds is to let them soak in a glass of water. The seed will absorb the water and due this process hormones will make the seed start to grow: expansion and elongation of seed embryo.
You will see them sprout after 24 to max. 48 hours. Note that you need to store the glass of water in a dark place on roomtemperature. After sprouting they are ready to plant in soil, 1cm to max 2cm deep. All they now need is love, light, water and heat!
Ready to sprout!
How To Germinate Cannabis Seeds: Wet (Paper) Towel Germination
The best known way of germinating cannabis seeds is to put them on or between wet paper towels or cotton wool. This method exists in different varieties, as it’s not so much about the paper itself, but more about the absorbency of the material. It’s very easy to make sure the ‘medium’ doesn’t get too soggy and doesn’t dry out easily. If it does dry, you can effortlessly add a few drops of water to immediately re-moisten it.
Wet paper towels are probably the most common way of germinating cannabis seeds
The goal here is to balance out the moisture so it’s not too dry, nor to wet. Go for a piece of paper that is moist all over, but doesn’t drip when you pick it up. If the seeds stay to dry, the root that’s supposed to sprout won’t be able to make it out of its shell in search for water. If the paper is too wet though, the root will come out and quickly stop looking for water; as it’s already soaked in it. This stops the development of the root, delays the growth and might even cause the seeds to rot after a while. So, be careful not to give too much water as this is one of the most common rookie mistakes when it comes to growing weed!
Transplanting In Soil
After the root has sprouted and has gained a few millimetres in length, it’s time to transplant the seedling into its soil and put it under a light-source. As a rule, a small 1cm deep hole made with your fingertip should do. Gently pick up the seeds one by one, taking care not to touch the root. Use a clean pair of tweezers and don’t squeeze. Make sure that the roots don’t cling to the paper or cotton wool. Lovingly cover the seed with a little (loose) soil and add a few drops of water. Now, all you can do is wait whole the story continues below the surface. As soon as the seedling pops her head above the ground and green leaves emerge, she’ll needf light to continue growing.
This is the part where most growers (especially the hasty ones) sometimes lose a seed. Remember that you are handling a baby plant here. The vulnerable root is easily damaged during the transplant. If you don’t trust your steady hands, it might be better to choose another germinating method.
How To Germinate Cannabis Seeds In Soil
Another common method of germinating cannabis seeds, and probably the most natural one, is to stick the seeds directly in their intended medium: the soil. You can do this with or without soaking it in root stimulator for a few hours first.
By planting cannabis seeds directly in their soil or coco – or whatever other medium you might be using – growers cause the minimal amount of stress for the plant. Direct planting also allows the taproot to immediately dive as deep into the ground as possible. Furthermore, its leaves can enjoy the light as soon as they emerge from the developing seed. This way the seedling can start its growth with a fair chance, providing you with a steady, high-yielding cannabis plant.
Cannabis seeds and sprouted seedlings require constant temperatures of around 20-25 degrees Celsius
For this method, simply prepare your medium by moisturizing it, again, without soaking the soil completely. Then take your flower pots and use your finger to make a small hole about 10-15mm deep in the top layer to put the seed in. Cover the seed up loosely and top it off with a little water. Be careful not to give too much at once though! A stream of water can cause the seed to travel further down the pot where it’s too moist – and too deep to travel back up again.
The top layer is the perfect place to germinate cannabis seeds, as it dries out faster than the soil further down the pot. This makes it easier to ensure the right level of moisture for the seed to germinate. If it gets too wet, the seeds will rot in the soil. If it stays too dry, the plant will not be triggered to emerge from its shell. Again, it’s all about finding the perfect balance between too wet and too dry.
How To Germinate Cannabis Seeds in Plugs
Last but not least on this list is the germination of cannabis seeds in special plugs. These plugs are available in various materials, especially designed for quick and efficient germination of cannabis seeds.
Plugs are a practical way to germinate cannabis seeds
Most plugs are dry blocks of (usually) coco fibre. Peat plugs are an interesting alternative, as these contain some initial nutrients to help the seedling along. After fully absorbing about 500ml of moisture, or 250ml of a root booster and another 250ml water, they slowly turn into a moist, soil-like plug. Grow plugs usually have a premade hole in which to place the seed. After sticking the seed in the top of the plug, cover it lightly with a little leftover plug fibre. It takes a few days at maximum before you see the first heads pop. As soon as the roots grow out of the bottom or the side of the plug, you can stick the entire plug, complete with its seedling, into your intended medium. These plugs make germination and the initial transplant a piece of cake.
A fantastic view on this seedling with it’s shell sticked to her leaves
After Germination: Growing Your Seedlings
So there you have it: whichever method you chose, germination should now be underway. Remember that even the best seed banks work with organic, natural materials, so 100% germination rates can never be guaranteed. If you get your technique right, though, most or all of your seeds should germinate according to plan. Once your seeds have become seedlings, the next steps of your grow await. There’s a lot of choices to make from here to harvest time: indoor or outdoor, which spot to pick, what nutrients to use, and so on. Keep an eye on our expanding grow blog collection if you want to learn more!
Germinating Cannabis Seeds – A Step by Step Guide
Germinating cannabis seeds is one of the most exciting parts of the whole grow. It is almost magical to summon new life from a dormant seed; however, it can be very frustrating when things don’t go well. In this article, I explain how to germinate cannabis seeds successfully. I begin by reviewing the science of germinating cannabis seeds. I then describe several common cannabis germination strategies and share some cannabis germination tips and tricks. At the end of the article, I provide my step-by-step guide to germinating cannabis seeds. Be sure to watch my Germination Tutorial on YouTube!
Germination will always be exciting, but it does not need to be intimidating. There are many ways to germinate cannabis seeds successfully. Understanding the science and the shifting needs of the developing plant will allow you to choose the germination strategy that is right for you.
The Science of Germinating Cannabis Seeds
Cannabis seeds are among the easier seeds to germinate. They are large dicotyledon seeds that store a reasonable amount of energy for early life. Furthermore, cannabis seeds do not have any significant seed dormancy factors to overcome. If they are viable seeds they will germinate easily when exposed to the correct conditions.
Seeds become Sprouts During Germination
This may sound obvious, but it is important to consider because seeds and sprouts are different. When the cannabis seed is still a seed, it is resilient and does not depend on ideal conditions to survive. However, sprouts are different. As soon as the seed cracks open and exposes the radicle (tip of the root) it becomes a sprout. As a sprout, it becomes much more sensitive to external conditions. Whereas the seed only needs warmth and moisture to germinate; the radicle on a sprout needs warmth, moisture, oxygen, and darkness to survive and grow.
Germination Stage 1: Imbibition
The seed’s journey to planthood begins by getting wet which starts the process of imbibition. Imbibition is similar to rehydration. When wet, the testa or seed coat of cannabis seeds imbibe water which causes them to swell and soften. The force of water entering the cells in the testa physically ruptures the seed coat and allows the radicle (root tip) to escape. The imbibition of water also activates the metabolic activity within the seed protoplasm.
Warmth is Required for Metabolic Activity
The metabolic activity within the seed will only activate if the temperature is in the appropriate range. Like other seeds, cannabis seeds will not successfully germinate if the temperature is too low or too high. Room temperature is warm enough to allow germination, but warmer temperatures enable more metabolic activity and faster germination. The ideal temperature range to germinate cannabis seeds is 80-86 F (27-30 C).
Germination Stage 2: Respiration
Seeds carry stored energy to help power metabolic activity and growth until the plant can begin photosynthesis. However, just like humans and other animals, plants must engage in respiration in order to convert that stored energy into active energy that the plant can use. During the earliest stages of metabolic activity as the seed awakens from dormancy, the respiration is anaerobic or without oxygen. However, the sprout needs to quickly begin using oxygen in aerobic respiration to continue to survive and grow.
As metabolic activity resumes, the sprout will begin to grow. Cannabis seeds store most of their energy in their cotyledons in the form of starches and proteins. The plant uses energy from aerobic respiration to digest these starches and proteins into simple sugars and amino acids, which it mobilizes to grow the radicle (root tip) and hypocotyl (stem).
Cannabis Sprouts need access to both water and air
Seeds can be completely submerged in water during the first part of imbibition. However, if they are completely submerged after the radicle is exposed then the sprout will die from lack of oxygen. As soon as the seed cracks open and exposes the radicle it needs to have access to oxygen for aerobic respiration. This means that it needs some contact with air. However, it also needs continuous contact with water. To achieve the best results in the sprout and seedling stages it is best to use a grow media that will trap both air and water. As I explain below, paper towels work well for this during the early sprout stage and germination media like Jiffy Pellets or Rockwool cubes are perfect for young seedlings.
Germination Stage 3: Orientation
At this stage of germination, the plant must orient itself to grow properly. The radicle must push down into the soil or media and the hypocotyl must push the cotyledons (first leaves) up out of the soil or media. Both gravity and light help orient the plant to grow in the proper direction.
Apply Light but Keep the Radicle in the Dark
Cannabis seeds do not require darkness to germinate. However, the radicle is sensitive to light. Bright light will stunt the radicle and can lead to a failed germination. When seeds are germinated in paper towels it is best to keep the sprout in total darkness until the radicle is about half an inch long (about 1.25cm). However, as the cotyledons emerge from the seed casing, they will be looking for light to indicate the direction they need to grow. Therefore, when the radicle is longer than half an inch it should be placed in media which will protect it from light. Once the radicle is safely in the media, light should be applied to the top of the media to signal the direction of growth for the cotyledons.
Germination Stage 4: Photosynthesis
During the germination stage the plant relies exclusively on stored energy from the seed. This energy is limited, so the plant must quickly begin producing its own energy through photosynthesis. The young plant works to establish its radicle in the media and push the cotyledons up into the light to begin photosynthesis. Once the cotyledons open and receive light, the plant will begin photosynthesis. At this point, germination is complete, and the plant can start producing its own sugars, starches, proteins and fats.
Nutrients for Germinating Cannabis Seeds
The nutrients and supplements that we provide to our plants are not their food. Nutrients and supplements support photosynthesis. Therefore, they are not needed until the plant has begun photosynthesizing. Indeed, adding nutrients to the water used for imbibition can actually inhibit germination. It is best to use plain water at a neutral pH (7.0) to imbibe the seeds.
Once the cotyledons are open, the plant can use very small doses of nutrients. However, it is easy to overdo it and burn the plant. When and how to begin fertilization depends largely on the media that you are growing in. If you are growing in coco or other inert and unamended media, be sure to read “How to grow cannabis seedlings in coco coir”.
Cannabis Germination Strategies
There are many viable ways to germinate cannabis seeds. Different germination strategies may be more suitable for different growers. Therefore, before explaining my step-by-step guide to germinating cannabis seeds, I will review some of the more popular germination strategies.
Many growers begin germination by soaking seeds in water. This allows for faster imbibition of the seed because it is surrounded by water. It is a safe strategy to follow as long as you remove the seeds from the water before the seed actually cracks open. If you soak seeds, you should use plain (low EC) water with a neutral pH (7.0). Filtered or distilled water is best.
The Paper Towel Method
This seems like a make-shift hack, but wet paper towels provide an excellent air/water ratio for germinating seeds. They also allow you to precisely control the temperature of the seed/sprout during germination. As a result, using paper towels can speed the germination process considerably.
The paper towels should be fully saturated with water, but not dripping wet. I like to fold the paper towel so that there are two layers below and above the seed. You can then place the paper towels in an air-tight container to prevent them from drying out. I use pyrex containers. If you use a plastic bag, just make sure that you trap some air in the bag (don’t squeeze all the air out). The radicle does need some air, but there will be plenty, even in a sealed container. Place the sealed container someplace warm and cover it to protect the radicle from light.
The main drawback to the paper towel method is that it is possible to damage the young sprout when you transfer it to media. There are some easy practices to mitigate this risk. First, use cheap, single-ply paper towels. This prevents the radicle from growing between the plies. Second, place only one seed on each paper towel. This allows you to pick up the whole paper towel and avoid touching the sprout when you transplant to media. Finally, don’t keep the seeds in paper towels for too long. Once the root has grown to about 0.5in or 1.25cm, it is time to transplant it to media.