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Caring for Cannabis Seedlings

Cannabis seedlings

Growing your very own (especially first) marijuana plants (or huge crops) is definitely one of the most exciting, entertaining, and sometimes stressful things that lovers of the wonderful herb can do. But, ensuring you care for the plant in each stage of the grow is crucial to creating a finished product that has a good yield and provides the high that you are looking for. 

During the cultivation process, you need to make sure you are caring for your marijuana seedlings in the correct way. Understanding how to handle them, what soil to grow them in, how much light to expose them to, and how much water they require, are all major aspects of creating the perfect plant. 

In this article, we touch base on the main things to look out for during the cannabis seedling growth stage, while also exploring some of the main issues to look out for and avoid in the seedling cultivation stage.  

Key Takeaways for Caring for Cannabis Seedlings

  • Use Organic Soil: Opt for organic cannabis soil as it is rich in complex microorganisms and nutrients, which reduces the need for additional feed solutions.
  • Coco-coir is another great option for new growers: It has a similar consistency to soil, but is made up of the fibrous husk of coconuts. You will need to add your own nutrients, but it is an excellent option for those looking to enter the world of hydroponics.
  • Monitor Light Distance: Ensure the correct distance between the light source and seedlings to prevent stretching while avoiding burning the plants. CFLs and Fluoros can be placed close, but HID and LED lights should be kept at least a foot away.
  • Watch for Pests and Insects: Regularly inspect your seedlings for common pests like fungus gnats, spider mites, and leaf miners that can cause substantial damage.
  • Transplant Timely: Transplant seedlings to larger pots when they have developed around 4 sets of leaves, roots start to entangle, or leaves cover the container’s circumference to prevent root-bound issues.
  • Avoid Overwatering: Overwatering can lead to root rot and other fungal infections. Ensure proper drainage and allow the soil to dry out between waterings.
  • Maintain Proper Ventilation: Good airflow helps reduce the risk of mold and mildew, which can easily affect delicate seedlings.

What is the Cannabis Seedling Stage?

Growing your very own marijuana plant involves four distinct stages. 

All of these stages require different types and levels of care. 

Once a cannabis seed germinates, you will hopefully see the tap root crack through the woody shell. This first root (the ‘tap root’) should be white and slightly ‘furry’, and needs to be handled with great care. 

No matter if you are growing in soil, coco, hydroponically, or any other way – get that seed and tap root “into the ground” asap. This begins the cannabis seedling stage, and the seedling should break ground in 1 to 4 days after planting. During this stage, you will see the plant develop and start to grow a stem with very small oval shaped leaves. These first set of leaves are different to the fan leaves that will follow. 

As the days go on, leading into the second week, you will start to notice the second set of leaves develop, which are the first set of ‘true fan leaves’ – the traditional fan leaf, zig zagged edge shape that we associate with everyone’s favorite plant. 

Throughout the cannabis seedling stage, be sure to keep a real close eye on your plants each and every day. The more you can recognize different growth patterns and growth stages, the more you will learn, leading to better cultivation prcatices as you continue your growing journey. 

One of the main things that you should look for are the number of blades or ‘fingers’ on the fan leaves. This will give you a good indication of what stage your plant is at. 

The first few sets of fan leaves will most likely only have 3 or 5 ‘fingers’, and actually, some strains may never produce leaves with more than 5 fingers, especially autos. 

The seedling stage is an extremely important part of the growing process, as the plant is still fragile and easily damaged. For this reason, you must take as much care as possible with your plants while they are seedlings, giving them as close to perfect growing conditions as possible, 

Coming up in this article, we have a closer look at the dos and don’ts of the seedling stage, including how much water to give your seedlings, how much light to expose them to and what temperatures and humidity levels are optimal for ideal seedling growth. 

Choose the Best Genetics, Medium and Containers

Choosing Your Seed Genetics 

One of the most important parts of sourcing your seeds, is to actively research and choose the strain that is right for you. So many of us love the sticky green stuff, from beginners to life-long stoners, those using it for medicinal uses compared to those using it recreationally. You might want it in the morning with your first coffee, or just before bed to help get your head down. 

The rec seed world and market are more extensive than ever before, offering Premium Cultivars that suit all types of smokers. Getting the genetics right is crucial to making the whole cultivation process worth it. From heavy Indicas, uplifting Sativas, quick-finishing autos, and everything in between, we have you covered. Only the best genetics here folks.

Do your research properly, and you will be harvesting buds that taste the way you want, smell the way you want, and most importantly, give you the high you are looking for.

Getting the Medium Right

Medium relates to the type of soil that you choose to grow your plant in. We recommend a light, well-aerated and slightly acidic soil (pH of 6.3-6.5 is perfect, but anywhere between 6.0 – 7.0 is fine), to deliver the most consistent and reliable results without too much fuss or hard work.

If you are interested in other growing media, like coco-coir or pure hydroponics, then by all means – get after it! Coco is a fantastic option, offering many of the benefits of both soil and hydroponic cultivation with cheap setup costs. It’s the perfect introduction to slightly more indepth cultivation, and will almost definitely result in better yields. 

We also suggest using anywhere about 30% perlite combined with your soil or coco, which will help with aeration, drainage, nutrient retention and spread, and the result is healthier, faster growth. 

Choosing the Best Containers

Choosing the right containers or pots for your plants can be a bit more of a complicated and tricky task.

If you are dealing with auto-flowering seeds, we suggest planting them directly into their final pots. They will grow fast and leave you little time to re-pot. They also don’t have the vegetative growth time to bounce back from the stress of repotting.

In general, we always suggest that soil and coco growers go with either smartpots or airpots. Both of these options allow for much higher oxygenation rates in the root zone, which boosts yields and healthier plants. 

But if all you have is some old plastic pots, and you dont want to spend any more money, then go right ahead. They will work just fine, just make sure there is enough drainage holes and you should be fine. 

What is the best Germination Techniques for Your Marijuana Seedlings? 

In order to grow healthy seedlings that will go on to produce high-quality buds that properly represent their respective strain, you first have to germinate your seeds correctly. In order to germinate, seeds need four things; moisture, darkness, warmth and time. We recommend using the following technique in order to germinate the best seeds possible. 

The Paper Towel Marijuana Seed Gemination Method 

  • First up, grab a shot glass, and fill it with pH-regulated (6.0 to 7.0) water, although tap water should also be fine. Drop your seeds in and leave for 6 to 12 hours, but no longer.
  • Once soaked, place your cannabis seeds on a moist paper towel, fold it over to cover completely, and then leave them in a plastic container with the lid clipped on. It’s important to make sure that the paper towels is moist but not dripping wet.
  • Place this container in a warm, dark space (25-30C / 75-85F). Check your seeds every 12 hours to see if the tap root has broken through.

How to Plant Marijuana Seedlings

When your seeds have opened up a slight amount, they will release small, white taproot. This is when you know they are ready to plant. Place them in your chosen soil mixture about 10 – 20 mm deep with the taproot facing down. 

The taproot will drive down into the soil and begin developing into a complex root system. Above the soil, two rounded cotyledon leaves will appear, which are responsible for absorbing sunlight, giving the plant the strength it needs to grow. As the plant absorbs more and more nutrients, that tiny, new born main stem is going to slowly but surely develop, and you will see the beginnings of the iconic fan leaves. 

How to Master the Seedling Stage

Seedlings are extremely fragile, armed with very few defence mechanisms to protect them from external stressors. Even the slightest pressure or strain on the seedlings can bring them down in a matter of hours. 

Taking the time to get to know your seedlings, what they need to survive and how best to protect them, will result in a greater chance of your seedlings making it to the vegetation stage. 

Over time, you are going to get to know your plants, how quickly they develop, and what they need. But let’s go over it right now, all the important stuff. 

Light

Seedlings are extremely sensitive to light, much more so than their adult selves anyway. When exposed to too much light, their leaves crinkle, burn, and wilt.

If they do not get enough light, the plants will grow tall and thin, and simply topple over without developing any flowers or buds. We recommend growing your seedling under an 18/6 light using an LED panel, but make sure the lighting rig is far enough away.

If you are planning on growing your seedlings outdoors, make certain they are exposed to as much direct sunlight as possible in a temp range of  22-28C (70 to 80F) degrees. If you can move them indoors at night to protect them from rain, cold temperatures, frost and wind, then definitely do so. 

Temperature

Similar to light exposure, seedlings are also sensitive to temperatures and humidity. For optimal growth, aim to expose your seedlings to temperatures of 22-28C (70 to 80F) during the day, but it’s fine if the temps drop to around 60F (15C) at night. 

High temperatures can cause extreme stress on your plants, stunting their growth and often killing the plant. Cold temperatures below 50F (10C) can shock the plant, and if it drops much lower (say nearer to freezing), the plant could die.

Humidity 

While the plant’s roots are young and still developing, seedlings absorb a lot of their moisture through osmosis in their leaves. For this process to be optimized, your seedlings must be exposed to relative humidity levels between 65-70%. The young plant could die if humidity is too high or too low for an extended period. 

Watering Your Seedlings 

As mentioned above, seedlings take up water through their leaves during the first few days, as their roots are not developed enough. For this reason, it is important to water your seedlings in a very specific way during these initial stages. 

  • Mist Your Leaves: A couple of times a day, you should use a light mist to wet your seedling leaves. This will help with the osmosis process and allow your seedlings to absorb all the water they require. Be sure to cover your seedlings with a plastic dome or bag, which will help them retain water and take up moisture. 
  • Water Around the Stem: In order to promote healthy root growth, you should never water the stem directly. Instead, you should apply water to the soil about 3cm away from the stem, in a circular motion. As the roots seek water, they will naturally grow outwards towards these areas. 

As the seedling stage progresses, the consistency with which you water your seedlings will change. Remember, there is no universal guide to when you need to what your seedlings. This all depends on the type of strain you are growing, whether you are growing indoors or outdoors, and the type of medium you have chosen to plant them in. 

As a general rule of thumb, you should water your plants when the soil has dried up. Simply stick your finger about 2cm into the soil to test whether it still contains moisture or not. In terms of when to water your plants, try to give them water just before you turn the grow lights on. These grow lights evaporate a small amount of water from the soil, reducing the risk of unwanted bacteria and fungal build-up. 

Another common question is “how much water to give your seedlings?”. 

Again, there is no universal rule for all plants, as there are many factors that affect how much water to give. However, you should generally never need to apply more than 1-2 cups of water at any one time. 

Growing Weed Seedlings Outdoors 

Growing seedlings outdoors exposes them to a lot more stressors, which means you need to be a lot more conscious and aware throughout the process. Growing seedlings out in nature also mean many more factors can change, resulting in potentially harmful outcomes. 

Weather effects such as wind, frost, cloud cover, or simple temperature changes can have a huge effect on your seedlings. Remember, seedlings are fragile and delicate, so should be looked after as carefully as possible. 

If you do choose to grow cannabis outdoors, timing is everything. You want to plant as spring begins to really crank, with temps around the 70 to 80F mark. Greenhouses can help protect the plants from the elements, giving you a better chance of a successful outdoor grow. 

Cannabis Seedlings Problems 

If you are a beginner grower, it is a good idea to be aware of some of the main problems to look out for. With a better knowledge of these potential issues, you will definitely give yourself a better chance of a successful crop run. Like all things, you will get better with experience, so don’t feel put off if you do come across some of these issues. It’s a learning experience and one with a pot of gold at the end of it!

Damping Off

Damping off is the name given to a fungal infection that affects your plants during the seedlings stage. It is one of the most common issues that growers face, so again, don’t feel put off if your seedlings are exposed to it. It is simply something you will need to be aware of for your next cultivation. The fungal infection causes the plants to go limp and soggy, which will cause them to eventually collapse and die. 

There is not much you can do to save your seedlings if they get this infection. As we mentioned earlier in the article, seedlings are super fragile, so any exposure to infections, especially ones as damaging as this, will usually result in the plant dying. However, if you are able to identify which of your seedlings have the fungal infection, you can remove them from the pots to stop other plants from getting it, too. This is another great example of why checking on your plants regularly is important

Nutrient Problems 

For your seedlings to blossom into beautiful buds, you will need to make sure they are given the right types and amounts of nutrients. The marijuana seeds themselves are jam-packed with nutrients to help them grow, however, when they run dry, it is up to you to step in and give your seeds what they need. 

We don’t recommend feeding in the seedling stage, as this can cause your seedlings to ‘burn’ due to soil that is too densely rich in nutrients. Instead, we suggest you leave your plants to chill and let them absorb all the nutrients from the soil, water, and light that they are given. If you are growing hydroponically, you will need to start feeding them once the first set of fan leaves emerge. 

Keep in mind the importance of transplanting your plants into larger pots for the vegetative stage. This is a highly stressful process for the plant, so give it some time to readjust to its new surroundings before you start feeding it fertilizer. Roughly 4–7 days is generally the timeframe that we suggest, to give your seedlings time to get used to their new home. After this, the vegetative stage begins, which is where the fun really starts. 

One more tip for avoiding nutrient problems is using organic soil. Different plants and different strains react to chemicals in different ways. Without fully understanding the complete effects of these chemicals, you could put extra pressure on your seedlings, resulting in them becoming stressed and potentially dying. Instead, use organic soil, which is rich in complex microorganisms. 

You may need to put a bit more effort into the cultivation process if you are growing organic weed, but nothing tastes quite as sweet as natures own. And the fact that the soil already has all the nutrients in there ready for the plant to gobble up, means you won’t need to worry too much about mixing up feed solutions every couple of days. 

Keep in mind that yields from organic mediums are generally lower than their non-organic counterparts. 

Pests and Insects 

Like all plants, pests and insects can have highly detrimental effects. Not only can they reduce the yield of plants when attacked in adult stages, but they can also cause plants to die in their early stages. Due to how fragile seedlings are, if pests and insects attack them during this phase of cultivation, they may very well be goners. Some of the most common pests to look out for include:

  • Fungus Gnats: These are very small, fly-like bugs that feed off of your plants. They also lay their larvae in the wet topsoil, which means they can spread through the whole pot, affecting multiple plants in a very short period of time 
  • Spider Mites: Thriving in hot conditions, these pesky insects live on the underside of leaves and spin protective webs around healthy foliage. 
  • Leaf Miners: They are known for leaving strange and irregular snail-trail-like spots on healthy leaves, which can stunt their growth. 
  • White Powdery Mildew: This is a type of mold that grows on the leaves of your plants and can spread quite quickly. 
  • Pythium and Fusarium are other types of fungi that attack the topsoil, quickly affecting the stems and root systems of your seedlings. 

Cannabis Seedling Stretching 

Cannabis seedlings stretch to get closer to light sources. This can be a big problem when growing indoors (or outdoors if the weather isn’t playing the game) and results in the stem of your seedlings becoming too long and weak. Without a strong stem, your plants have a much lower chance of thriving in the vegetative stage and can eventually slump and die. 

To avoid stretching, you need to get the distance between the light and the seedling right. Too close, and you will likely kill the little lady from too much light, but too far, and she will stretch. CFLs and Fluros can be placed super close (say 2 inches or so), but HID and LED will need to be at least a foot above, if not a little further. 

When to Transplant Marijuana Seedlings 

When our plants are at the seedling stage, they are small, delicate, and fragile and belong in small pots. These small pots give the seedlings the best chance of absorbing the right amount of nutrients and water. However, there will come a stage when these seedlings are too big for the small pots and need to be transplanted into something bigger. 

Unfortunately, transplanting your seedlings is not an exact science, and there is no perfect guide you can follow that will tell you when exactly to move your plants from their small pots to the final pots where they will grow into the beasts we all hope for. It is all about recognizing cues. 

The biggest thing to avoid is the plants becoming root-bound. This is where the root ball becomes so tangled that it starts to choke the plant’s growth. The pot becomes filled with roots, leaving no room for water or nutrients. If you find your plants are becoming root-bound, it is definitely time to transplant them into bigger pots before they become too stressed and burn out. 

Some of the main ones you can look for include:

  • Your plants have developed 4 sets of leaves 
  • The roots start to entangle each other, or begin to protrude from the pot
  • Their leaves fully cover the circumference of their container 
  • You can completely remove a seed from its soil without damaging its root system

The timeline for transplanting seedlings changes depending on the strain and the conditions that it has grown it. A general rule of thumb is 2–3 weeks for the seedling stage, before it is ready to start fully vegging. 

Final Thoughts 

It would be somewhat understandable, after reading this big blog, that you may feel a little overwhelmed by the process of growing weed/pot/ganga seedlings.

Don’t stress out too much. As long as you germinate them in a paper towel, get them straight into some good soil (or whatever your preferred growing medium is) as soon as the tap root pops out, and then treat the baby plant like the queen she is about to become, then it’s really not that complicated!

Even with careful attention to soil, nutrients, and light sources, pest and insect infestations can still happen. It’s important to regularly check your plants for signs of pests, and act quickly if you see any signs of things going south.

Growing weed, especially as a hobby, is supposed to be fun, right? Enjoy the process because there really aren’t too many things more satisfying than watching a little seed grow into a big, healthy plant bursting with crazy buds. So, get out there, grab some great seeds, and get your trimming scissors ready for harvest!

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Sam North

Sam North is a content writer with a passion for everything cannabis. After working multiple seasons on weed farms absorbing the ins and outs of cannabis cultivation and culture, he decided to transition into a role that would allow him to work from anywhere, anytime. Sam now writes for multiple weed publications. He has extensive experience with a wide range of canna-agriculture styles, from smaller artisanal farms to large-scale commercial operations, and is here to share his knowledge to give you all the best chance of cultivation success. About this Author

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