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Liquidseaweed and germinateing cannabis seeds

How to Germinate a Bag Seed

F inding a seed in your bag of weed used to be regarded as an insult, an indication you scored some inferior product. But it’s a new millennium, and growing cannabis is perfectly legal in some states and territories. While buying seeds online is still recommended for reasons we will detail further, finding a healthy seed can be as valuable as an ounce of gold. Or at least the cost of the bag.

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In this article we review the steps to germinate cannabis seeds, tips and tricks in the process, and how to keep your seedling healthy.

Germinating a seed is the first step in the growing process, and a cannabis seed will sprout with a voracious hunger, so if you are about to germinate seeds, start thinking ahead about where the seedling will eventually be moved to. This includes lighting, ventilation, and something to feed the lady. Those things don’t need to be decided before you begin, but try to have a plan in place by the time the second set of leaves emerges — as soon as two weeks.

The Germination Process

Begin by soaking the seed overnight. Soaking the seed saturates it with moisture, and moving it shortly after to a warm home tells the seed that it’s someplace comfortable, and it’s time to grow. Tap water is fine for this, but a micronutrient solution like liquid seaweed may be included.

Once your seed has soaked, the most common method for germination is the “paper towel method.” Wet a piece of paper towel and wring dry, then fold in half. Place the seeds between the halves of the damp paper towel, and slide the whole thing into a ziplock bag. Seal with some air inside. Leave this bag someplace comfortably warm for about a week, checking frequently for spots of mold. After about a week, a taproot should emerge.

Then it is time to transfer the seed into a proper growing medium. Be careful plucking your seed from the paper towel!

A grow medium is the “stuff” the seed will sit in. The easiest option is soil, healthy black earthy scooped up from your yard, or potting soil purchased from any garden center. Rock wool cubes are a common option for hydroponic growers, but can later be transplanted into soil as well. Compost and worm castings are great for a seedling, but it will need to be transplanted into a more diverse mixture later.

It is far too early to begin any nutrient cycle, or to introduce any fertilizers to the soil. Now that the seed is confirmed as alive, and placed into a more comfortable medium, simply make sure that the seed is watered and warm.

The first set of leaves to emerge are called “sucker leaves,” and their sole purpose is to drink in as much light as possible to fuel the growth of the more recognizable serrated leaves, which will begin to grow over the next week. After that you’ve got a proper seedling, and in a few weeks it will be ready for a bigger home!

For further guidance and resources about growing cannabis, see our Beginner’s Guide to Growing Marijuana, or our guide to growing for personal use.

Cultivating a Healthy Cannabis Seedling

The seedling that emerges will be as tender as an infant, and susceptible to diseases and cross-contaminations, so keep your germination station as sanitary as possible, and wash your hands before handling them. Avoid rubber or latex gloves at this stage as they have too much grip, and one wrong movement of your finger could accidentally grab and tear the soft plant material.

A seed’s health may be fortified by soaking it with a solution rich in micronutrients, like liquid seaweed. Be advised, however, that these will be very diluted solutions. Carefully read the mixing instructions of any product you purchase.

Seedlings can be protected against certain diseases by including worm castings in the medium. Research out of Cornell University has shown the microbial life in worm castings colonizes the seed’s surface, making it more difficult for pathogenic microbes to establish themselves.

Disclaimers and Downsides Regarding Found Seeds

It’s worth pausing to remember that seeds shouldn’t wind up in your bag of cured, smokable cannabis. So before planting anything, let’s assess what this seed is, and how it got there.

Only female cannabis plants produce flowers, and if they are pollinated by male plants, then they produce seeds instead. So all the cannabis we smoke is from unpollinated female plants — or nearly all of it.

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When female plants are stressed — for instance, by drought conditions or nutrient problems — an evolutionary alarm can induce them to produce seeds with only their DNA. The problem with these “hermaphrodite seeds” is that the offspring, having benefited from this process, will be more prone to repeat it. If this is how a seed got in your bag, it can result in seedy weed, even under the closest care.

A seed is not guaranteed to sprout at all. Examine the seed for any obvious health issues. Immature seeds are lighter greys-to-green, while mature seeds are darker tan, brown, or even black. A healthy shape is a teardrop or nearly round, while bunk seeds will appear shrivelled or irregular. Finally, healthy seeds have a hard, whole shell, while cracked or brittle shells will likely not sprout, or produce a less healthy seedling.

A found seed is also not a guarantee to produce a replica of the strain you smoked, and may present latent traits from the strains it was bred from. Cultivating a complete copy of a phenotype is called “cloning,” and the cloning process must begin with a living plant, not a seed.

Remember, it could also just result in a male plant, which won’t grow any buds. None of this is guaranteed to happen with a bag seed, it’s just more likely than with a stabilized seed from a producer.


If you want to germinate a seed you’ve found, begin by soaking it overnight in water to saturate it, and soften the shell. Micronutrient solutions can be mixed in at this stage to fortify the health of the seedling (if you do, be sure to read the mixing instructions on the label).

The “paper towel method” is the most accessible way of germinating almost any seed. Once a taproot has emerged (after about a week) plant the seed into a small container with your chosen grow medium, like soil. Do not fertilize at this stage, as the seed and resulting seedling are very tender, and concentrated fertilizers are abrasive chemicals. Within another week, “sucker leaves” will sprout, synthesizing light to produce further growth.

Remember, found seeds are not always healthy or even viable. A healthy seed has a hard, unbroken shell and a dark color, while brittle or misshapen seeds may not produce a healthy plant, if anything at all. A found seed is also not guaranteed to replicate the precise phenotype of that cannabis you found it in.

That said, it’s almost always worth trying, and experimenting with whatever results. Growing cannabis can be an enriching experience, and perhaps even save you some riches. As long as you know what to look for from a seed, and how to handle them, finding one in your bag could be a golden ticket.

How to Feed Seedlings with Seaweed Extract Fertilizer

If your new baby seedlings are a few weeks old now, it may be about time to feed them for the first time! In best practice, seeds are sowed in very mild, light, fluffy seedling starting soil mix, which is generally pretty devoid of nutrients. That is fine (for now) because tiny seedlings do not need or like fertilizer in the first couple weeks after sprouting. It can actually harm them, or “burn” the seed and prevent germination!

On the other hand, as they begin to grow, that fluffy seedling mix quickly becomes too light and won’t be nutritious enough to keep them happy for very long. Fertilizing seedlings with seaweed extract can help solve that! It is gentle, sustainable, and effective.

Let me show you how we fertilize our seedlings seaweed extract fertilizer to help keep them healthy and strong! It is very simple, and will make for a pretty quick post! At the end, you’ll find a demonstration video.

When do I start to fertilize my seedlings?

Seeds are pretty amazing little things. The seed itself contains all the food and nutrients that the little plant they produce needs for those first few weeks after sprouting. But as they start to mature, they’re also going to start to get hungry. Like any good baby should, they will get very cranky if you don’t feed them when they want it. Signs of distress include yellowing leaves, stunted growth, and even disease or death.

The best time to start fertilizing your seedlings is before they begin to get cranky. It is a lot better to keep them satiated then wait until they’re in trouble, and try to correct the damage. This is sort of a Goldilocks and The Three Bears kind of story. Not too early, not too late, not too much. We want “just right”.

Wait until after first couple sets of “true leaves” appear, and then start to feed them very lightly. About 3 to 4 weeks after germinating is a good target, about the time you’d want to start to thin them also.

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What are true leaves? When a seed germinates, the first set of little leaves that emerge (often heart-shaped, and often looking exactly alike between dozens of varieties of veggies) are not the true leaves. These are the cotyledon leaves – their embryonic leaves. The two leaves that come after the cotyledon are their “true” leaves. Those leaves will more closely resemble what the mature leaves of the plant will look like.

These seedlings are TOO SMALL to be fed any fertilizer yet! The image in the top right show the heart-shaped cotyledon on a bunch of broccoli, bok choy, kale, and mustard greens. The lower right are tomato sprouts, and the on the left is a tomatillo. Wait another week or two, until the true leaves become larger and another set starts to appear.

If you’re going to plant your seedlings outside or pot them up within a few weeks after germination, it may not be completely necessary to feed them in their starting container. When they are planted outside in a bed of rich soil, or into a larger container with fresh soil and compost, they’re going to be essentially “fed” in that process. Yet if you are like us, and keep seedlings in containers for two or three months before planting them outside, they’ll definitely want a few rounds of food during that time.

What should I fertilize my seedlings with?

Many gardeners, us included, like to use a dilute organic seaweed extract fertilizer. It is nice and mild, making it very difficult to shock or harm your seedlings unless you really overdo it.

Seaweed extract helps the plants grow bigger and develop stronger root systems. Both of these contribute to overall improved plant health and immunity. Just like people, a plant with a strong immune system has a stronger ability to fight off disease, pests, or rebound from stress. Seaweed extract is loaded with over 70 beneficial vitamins, minerals, micronutrients, and enzymes! It contains magnesium, potassium, zinc, iron and nitrogen – to name just a few.

Cold-pressed kelp is commonly used to make seaweed extract. The harvest and cultivation of kelp is widely recognized as sustainable and environmentally-friendly! This is an excellent (and often overlooked) multi-purpose fertilizer; one that can be used for much more than seedling care! When we don’t have time to make a batch of compost tea, we water our garden beds or house plants with it too. Additionally, seaweed extract can be used to make foliar sprays. The plants can then absorb all that good stuff straight through their leaves.

Edit: We used to use this seaweed extract (at the time of writing this post), but the formula recently changed and it no longer says OMRI listed for organic gardening. I’m not sure what’s up, but we since switched to this organic seaweed extract instead.

From the book “Seaweed Sustainability” – Academic Press:

“Seaweeds grow in abundance in the oceans, many of which are edible and safe for human consumption. They have been documented to contain many of the essential nutrients such as omega-3 fatty acids, amino acids, vitamins, minerals, and bioactive compounds.

For many years, seaweeds have also been cultivated and utilized directly as food for humans or as feed to produce food for human consumption (e.g. fertilizer). Since seaweeds grow in many climatic conditions globally, their cultivation has minimal impact on the environment. Seaweeds are increasingly recognized as a sustainable food source with the potential to play a major role in providing food security worldwide.”

Kritika Mahadevan, Chapter 13 – Seaweeds: a sustainable food source

Kelp is such amazing stuff, that in addition to feeding it to our plants, we take some for ourselves too! No, not this liquid fertilizer… but in the form oral supplements. Algae is the only plant-based, vegan, or vegetarian source that contains all the most beneficial and essential forms of omega 3-fatty acids that are usually lacking in other plant sources. If you’re curious, read all about that here.

Another option people use for fertilizing seedlings is liquid fish emulsion. We don’t personally use this, so I won’t speak on its behalf.

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How do I feed my seedlings seaweed extract?

Mix the seaweed extract with water according to the instructions on the bottle. If possible, use de-chlorinated water on seedlings. We use captured rainwater. If you allow chlorinated water to sit out, like in a bucket for example, the chlorine will dissipate in a day or two. If your city uses chloramines instead of chlorine to disinfect their water, it won’t burn off. When we can’t use our rain water, another option is to hook up this basic RV carbon filter to a hose – and that takes care of it.

Some types of seaweed extract have varying instructions for different types of plants or stages of growth. Look for instructions clearly intended for seedlings, or as a soil drench. We use about an ounce per one gallon of water, maybe just a touch over that sometimes.

Personally, I like to mix it inside this one-gallon watering can, especially for watering seedlings or working in the greenhouse. It is easier to handle than a larger 2 gallon can, and I really love the long, curved, skinnier spout. The design makes it very convenient for watering from below, as described next.

Wait a few days after the last time you watered, until the plants are getting a little thirsty and are due for another routine watering. Now, feed the seedlings the dilute seaweed extract mixture in place of their regular water. To accomplish this, we prefer to water from below.

Watering from below, into the trays. A note about our seedling trays: we prefer to use these heavy-duty seedling trays. They’re incredibly durable, will not crack, and can even hold bricks without bending! In addition to their longevity and strength, they’re perfect for watering from below. We still have some older flimsy 10×20 trays that aren’t totally “broken” and fairly functional, but this year I noticed most of them have developed little pinholes in the corners! This means all the liquid leaks out when practicing watering from below. And…. I figured this out the hard way, using a tray inside!

Feeding seedlings seaweed extract from below:

If you aren’t familiar with the concept of “watering from below”, it is exactly what it sounds like. It’s accomplished by pouring water (or in this case, seaweed solution) into the tray the seedling containers are sitting in. The soil will draw up moisture from the bottom, soaking up as much as it needs until the soil is evenly saturated.

Simply pour enough seaweed solution to evenly fill the bottom of the tray (with the containers still sitting inside of it) to about a half an inch deep. It is important that your trays are sitting level to ensure all the seedlings are getting a similar amount of seaweed solution. Otherwise, the liquid may pool on one side and leave the other thirsty.

After adding the seaweed solution to the tray, wait about an hour to see what happens. Did they already suck it all up, but seem a bit dry still? If so, you may need to add a little bit more. Alternatively, is the soil totally saturated, but a lot of liquid remains in the tray?

Allowing seedlings to sit in soggy conditions is not ideal. They breathe through their roots and do not want to drown. Therefore, we try to remove any leftover standing liquid from the trays within a few hours. Or, at least by the next day if we get busy. You can do this by either very gently tipping it out (if possible), or using a large garden syringe thing to suck it out. Yes… it is easiest if you don’t have a bunch of excess, so I suggest to go lighter at first and add more if needed.

How often to feed seedlings seaweed extract?

You can generally feed seedlings seaweed extract every two to three weeks, depending on the brand. Again, read those instructions! After feeding, you should see an immediate boost in growth.


It is as simple as that. If you follow these steps to feed your seedlings, they will thank you and feed you right back!

Check out this video to see just how quick and easy it really is.

Do you need more seed starting and seedling care tips? Check out this post all about starting seeds indoors! Furthermore, here is another one that covers how to thin seedlings when the time is right.

In all, I hope you found this interesting and informative! Let me know if you have any questions.