The foundation of healthy growth starts with genetics and care for marijuana seedlings. Here’s all you need to know about the cannabis seedling stage. If you want to learn about the different elements that can affect your cannabis seedlings, how to identify the problems and fix them, make sure to read along! Marijuana Seedlings Now that your marijuana seeds have sprouted, what’s next? How do you care for your little baby marijuana seedlings? Your germinated seeds must be placed in a more suitable
All About the Cannabis Seedling Stage
Cannabis grows in stages: germination, seedling, vegetative, and flowering. The first phase is germination, which happens in the first 3 to 10 days. Next comes the cannabis seedling stage in weeks 2 to 3.
Following is the vegetative stage that lasts from week 3 to 16 weeks. The final one is the flowering cannabis phase at weeks 8 to 12. The vegetative and flowering stage tend to happen simultaneously, as new growth and more mature leaves live on the same crop.
One of the most critical phases is the cannabis seedling stage because the weed plant is vulnerable and growing rapidly. Is your harvest currently in this phase, and you need to know more? Read on to find out everything you need to know about the seedling phase of marijuana.
What is the cannabis seedling stage?
Your cannabis plant enters the seedling stage when the seeds begin to sprout. The shell will split, and a tiny white tendril will start to poke out. Soon a tiny stalk will emerge from the growing material, and more roots will grow downward.
In the latter days of the seedling stage, the initial two leaves will form at the top of the stem. The weed plant will continue to develop upward with more leaves, and the roots will become stronger until it enters the vegetative stage.
During the cannabis seedling phase, the crop is very weak and prone to diseases. If not taken care of properly, the marijuana plant might die or not continue growing. This is one of the most interactive stages in the crop’s life.
How to choose the right container, medium, and genetics for your seedlings
The right container
When you’re looking at what container you should plant your cannabis seeds in, there are a few things to consider. Let’s take a look at different types of marijuana seeds and where to plant them.
For autoflower weed seeds, you should put them in the final container that they’ll grow into the vegetative and flowering stage. Autoflower strains have a short life cycle, so you don’t want to put them through any unwanted stress from transplanting. For more details, check our “autoflower pot size” report.
If you have feminized seeds, start them in germination pots to ensure they’re healthy in the initial part of life. The marijuana plant can stay there through the seedling stage. Transport the crop once leaves start to form that are bigger than the container.
For all types of containers, you want to make sure that there are drainage holes, aeration, and the proper size for the types of marijuana strain. Seedlings do well in propagators.
Drainage is essential because still water will encourage mold, fungi, or other pathogens. This can be deadly for small seedlings. Aeration is vital because roots need to breathe too. It results in healthier and faster growth.
To determine the correct pot size, you need to do some homework. Read up about the cannabis strain, how big it should grow, and for how long. Too big of a container, there’s a risk of overwatering and malnutrition. Too small, the roots can’t grow enough, which can result in stunted growth.
At the beginning of cannabis life, you want to use a light and slightly acidic medium. The pH needs to be between 6.3 to 6.5. The growing medium has to be well-aerated as well.
You can add 20 to 50% of perlite to the medium to help with nutrient (nute) retention and aeration. Seedlings are sensitive to nutrients. You don’t want to shock your cannabis plant with a lot of nutes in the beginning.
You can use any potting material for growing seedlings, and it’s just important to keep an eye on these factors.
Genetics of your seedlings
Growing marijuana takes a lot of work and knowledge. Understanding the genetics of your weed seed will help you provide quality cannabis seedling care.
Some cannabis seedlings need more light, nutes, or space to grow than others. Other cannabis strains grow taller, and some grow wider. Certain marijuana types grow better indoors than outdoors, or vice versa.
Do your homework before planting your weed seeds to ensure you’re doing everything correctly. If you’re a beginner, look for low-maintenance, stable strains, so you can learn how to grow marijuana without other factors.
What factors lead to healthy cannabis seedlings?
Now you have the correct container, growing medium, and know about your seedling’s genetics, it’s time to look at care. All marijuana growers want successful seedlings because this is the first stage of life and what sets the stage for the rest of their existence.
Watering and pot size
Watering weed during the seedling phase is very important. You need to find an adequate amount of H2O based on the pot size and drainage.
Symptoms of an overwatering cannabis seedling problem include dropping seedlings, a very moist growing medium, and damping off. The reason for this could be that the container is too big for the seedling. Another could be that the pot size is correct, but the drainage is bad, or you’re watering too often.
Signs of underwatering are wilting seedlings, a dry growing medium, and slow growth. The leaves might look crispy or be fading in color. To correct this, you need to up your watering schedule.
You can tell a healthy amount of moisture when the growing material still looks damp after watering. You determine the pot size based on the strain of marijuana. Most growers will use a sprayer to water their weed crops during seedling to prevent overwatering.
Cannabis seedlings need plenty of light to grow. They produce energy through photosynthesis, which requires sufficient rays to work.
In some areas, natural sunlight will be enough to grow healthy cannabis seedlings. However, if you live in the northern USA, purchasing artificial growing lights is essential. The weed season is shorter in those parts of the country because of the light and temperature.
Regardless of where you live, if you have an indoor garden, extra lighting is almost always needed because windows don’t let in sunlight all day. A cannabis seedling light schedule is 18 hours of sun each day with 6 hours of darkness.
The temperature for growing weed is essential for the proper growth of cannabis seedlings. When the degree is too high or low, the roots can’t absorb nutes, which leads to a deficiency, stunted growth, and death.
A hot 73 degrees Fahrenheit is the correct cannabis seedling temperature. It’s vital to remember that many things put off heat, such as humidifiers, lights, or other electronics in the room. Take this into consideration when setting the temperature in the room.
If the garden is getting cold a lot, look at the ventilation system, cracks in the windows, or any other areas that could let cool air in.
You might be thinking that you need to load up on cannabis nutrients during the seedlings stage, but that’s not the case with marijuana.
Giving the cannabis plant too many nutes will result in toxicity. If this happens, watering will help dilute the growing medium. It’s better to look for fertilizers that are slow-release to avoid this from happening.
On the other hand, fragile young marijuana can experience a deficiency if you’re not giving them enough. A nute deficiency will result in the yellowing and folding of leaves. You’ll be able to tell more on the bottom leaves.
Buy a balanced fertilizer to ensure the cannabis seedling nutrients are provided but not overdosed.
Common causes of stunted growth in cannabis seedlings
If you see signs of stunted cannabis seedling growth, there are some direct causes.
- Seedlings not getting sufficient light during the day.
- The temperature of the garden is too hot or cold.
- The humidity level isn’t correct. It should be 40 to 60%.
- Water or growing material suffocates the roots.
- There’s a nutrient deficiency.
- A pathogen, pest, or other unwanted factor is attacking the plant.
- Genetically, this marijuana strain is small.
Look at these areas and adjust if you find a problem.
How to prevent nutrient problems
During the cannabis seedling stage, it’s essential not to overfeed or water. Use proper marijuana nutrients, but don’t give the full strength until the crop is mature. Instead, dilute the fertilizer to about 10 to 15%.
This will ensure that the seedlings are getting nutes to grow but not in toxic amounts. If you accidentally give too many nutrients, flush the cannabis plant. Make sure there’s excellent drainage to avoid water buildup.
How to avoid stretchy seedlings, pests, and bugs
Stretched out cannabis seedlings won’t produce sturdy stems needed to support leaves and buds. This happens where there isn’t enough light, and the marijuana plant is trying to get closer to what there is. If the temperature is too hot, this can happen.
To avoid stretching out, make sure your garden has sufficient light on all parts of the plant, not just above. Next, monitor the heat to be about 78 degrees at all times.
If your seedling is already stretched, bend it back and forth. This puts some stress on the stem, and it’ll rebuild stronger. When leaves start to grow, they’ll be able to handle the weight.
Pests and bugs love warm and humid areas, which is the same environment marijuana thrives in. To avoid this, make sure there’s no standing water and the ventilation system has a screen. Bugs won’t be able to enter the garden if it’s secure.
If they’ve already made their way in, use a trap or organic food grade pest control chemicals to kill them. Look for holes or areas that are letting them get in and patch them up.
When and how to transplant cannabis seedlings
If you’re growing cannabis seeds in a different container than what you’ll use when it’s mature, you need to transplant cannabis seedlings.
First, have all of the materials you need to transplant ready to go. These include water, pots, growing material, a butter knife, and a marker.
Before starting, water the seedlings, as wet soil is easier to work with, resulting in less damage to the roots. Gently, slide the buttle knife around the seedling’s container to loosen it. Never tug hard. The roots and soil should slide out without a lot of pulling.
Have the new pot nearby to plant and transfer. Tap the soil a little, so the seedling is now secure in the new growing medium. Label the container, so you know which cannabis strain it is. Water with light nutes and let them settle in.
The end of the seedling stage
The marijuana plant is out of the cannabis seedling stage when it starts to form real leaves. This happens after about 3 weeks of growing.
You then enter the cannabis vegetative stage, and need to follow a whole new procedure. Now you know everything about growing happy and healthy seedlings, it’s time to buy cannabis seeds and get planting today!
About the author: Kyle Kushman
13 times Cannabis Cups winner. Kyle Kushman is a master breeder and indoor growing expert, a leading voice in the fight for legalisation and education, especially when it comes to growing cannabis at home. He’s been teaching and spreading the word for over 30 years, maintaining a consistently high level of achievement throughout his entire career.
Common Cannabis Seedling Problems and How To Fix Them
Problems with seedlings are common and can end up affecting them further into their life cycle so it’s vital you detect and fix them as soon as you can. Yellowing or deformed leaves, burnt tips, or even slow growth are signs of cannabis seedling problems, even though your seedling may be able to recover, it may have a toll on the final size and yields of your cannabis plants. It’s definitely not hard to detect when something’s wrong, but if you’re a new grower, first you should know what a healthy seedling looks like.
1. Healthy Cannabis Seedlings
Cannabis seedlings start with two tiny round leaves called “cotyledons”, these leaves are already formed inside the seed and open up once the seed has been successfully germinated, after a couple of days, the first serrated leaves will appear, which indicates that your weed seedling is starting to grow.
As your seedling start developing, the first pair of true leaves will appear, the true leaves are the typical fingered leaves everybody knows, all of the leaves up to this point should be bright green, if not, it’s a sign that something is wrong, to help you diagnose what you may have, here are the most common cannabis problems.
Overwatering is one of the most common cannabis seedling problem amongst growers, even though weed plants need water to grow, they also need oxygen to properly develop, and when overwatering, you may end up drowning your plants because of the lack of oxygen. What about plants grown in hydroponics? Well, in hydroponic setups, about ⅓ of the roots are kept out of the water, this way they can breathe at the same time that they absorb water so even though the roots are in the water, they still get the oxygen they need.
When your plants don’t get the amount of oxygen they need, the leaves will start getting droopy and if you don’t treat it for long, the leaves will start to get yellow. If you are seeing any of these symptoms, it’s most likely the problem is being caused by any poor drainage or watering too often.
How to fix it
- Don’t leave plants sitting in runoff water.
- Get better containers such as Smart pots or Air pots.
- Mix perlite into the soil to increase drainage and oxygenation.
- Make drainage holes on the bottom of the container to allow water to drain.
Just like overwatering, underwatering is very common, especially among new growers who want to prevent overwatering and it can be quite confusing because the symptoms are basically the same as when overwatering.
It’s essential you ensure your plants have access to water at all times, the roots should be kept moist always because plants are constantly losing water through the process of transpiration and they need to be able to replenish the water in the leaves. When there’s not enough water, cannabis plants stop performing their basic processes and dry out, eventually killing them so even though you should be careful when watering, you should definitely keep your plants watered to avoid seedling problems.
How to fix it
- Ensure the top part of the soil is always moist.
- Mix soil with coco fiber or vermiculite to improve water retention.
4. Nutrient Problems
Just like the symptoms of overwatering or underwatering, plants that suffer from a nutrient excess (overfeeding) will start to get yellow leaves or yellow spots, burnt tips, or show slower growth. Seedling problems related to nutrients are usually caused by giving nutrients too soon, giving too many nutrients at once, or “hot” super soil or pre-amended soils. Giving too many nutrients at a time can cause problems overnight, so we recommend watering your seedling with plain water and taking a look at the following table so you prevent any seedling problems related to nutrients.
|The ideal water for seedlings|
|Coco, clay pellets, and hydro||5.5-6.2||300-400|
Have in mind that these are estimates and you should check every day for problems and lower or increase these numbers if you see signs of deficiencies. Giving nutrients too soon will overload the soil, and consequently, your seedling so remember that you shouldn’t feed for the first couple of weeks or at least give a low nutrient dose.
This can also happen with organic super soil, even though it’s organic, you need to wait until your super soil isn’t “hot” anymore, “hot” soil means that the mix is still undergoing biological activities so you will have to wait around 30-45 days before you can use it, although this is not the case with all super soils so make sure you get more information on the product you’re using to avoid seedling problems.
How to fix it
- Ensure you adjust the nutrient dose according to the medium you’re growing in.
- Wait at least 10 days before you start feeding your plants.
- Read the instructions on the products you’re using.
5. Excessive Heat
Excessive heat can also affect your plants, which will end up showing signs of heat stress, you will see the edges of the leaves turning up like tacos and they will start to get dry and crispy, and in more extreme cases, the leaves will start showing a yellowish-green color.
This can be caused by elevated temperatures, low humidity, or even the fans being too strong, but luckily, this can be easily spotted before your plants start showing the symptoms because you will see the soil is dry and sometimes it will start to crack.
How to fix it
- Make sure the temperature and humidity are at the right levels.
- Place your hand under the light fixture, if it’s too hot for you, it definitely is for your plants.
- Ensure your fans are not too strong for the stage your plants are in.
6. Too Much (or Too Little) Light
Another common problem among new growers is not providing enough or providing too much light in the seedling stage, if your seedlings are not getting enough light, they will start stretching and the stem will get super long, which is a bad thing because they can easily snap and there’s no way to fix it.
Now, when your seedlings are getting too much light, or the lights are too close to them, the seedling will get dehydrated and the leaves will get burnt, showing symptoms like burned and wrinkled leaves.
How to fix it
- Adjust the light fixture’s distance from the seedling every day, try to find the sweet spot.
- Use CFLs instead of potent LEDs or HPS to avoid this kind of problem.
7. Seed Shell Stuck on Seedling
Sometimes, when a seedling comes out of the substrate you’ll see how the seed shell is stuck on the seedling and won’t come off naturally. When this happens, your seedling won’t be able to develop properly and you’ll probably see a lot of stretching, and if left for too long, the seedling can end up dying. This happens because of the humidity levels, so in order to minimize the damage, there are a couple of things you can do.
How to Fix It
As mentioned, this happens because of humidity levels, low humidity levels to be precise, so what you need to do is hydrate the seed shell. So go ahead and spray the seedling with plain water or just drop one or two droplets of water on the seed shell, this will hydrate it enough for the seed shell to fall off. Keep in mind that sometimes the seed shell falls off but a membrane covering the cotyledons can remain stuck and your seedling will not be able to open so make sure to grab some tweezers or remove the membrane with your fingers but do it very, very carefully.
If you need to do it asap and don’t want to wait for the seed shell to fall, you can remove it by hand without spraying it but keep in mind that if the seedling’s roots have not grown enough, you can end up removing the seedling from the soil so do not use excessive force. It’s highly recommended to hydrate the seed before just to avoid shock or stress, especially to avoid removing the seedling from the substrate completely.
- Make sure to keep the humidity levels in range with the help of a humidifier.
- Place a plastic dome (like a cut-out plastic bottle or plastic cup) on top of the seedling to help keep higher humidity levels.
8. What To Have in Mind During The Cannabis Seedling Stage
In order to avoid all the cannabis problems mentioned throughout the article, here are the main tips that will help you avoid them and keep your cannabis seedlings healthy and happy.
The Perfect Environment
The relative humidity and temperature will directly affect how your seedling grows so make sure the light is not too strong but your cannabis is still getting enough light and the temperature is around 21-23 ºC and the relative humidity ranges from 70-80%. Failing to provide good conditions can affect plant growth and can ultimately kill your plants if left untreated for too long, so here’s what to expect in the different conditions:
Substrate is too wet
If the substrate is too wet, the seeds can drown. Despite seeds being germinated in water, it’s not okay for the substrate to be extremely wet so always make sure the substrate is moist but not soaking.
Substrate is too dry
Cannabis seeds need moisture to germinate so make sure the substrate is moist but not excessively wet as excessive dryness can make your seeds not germinate and die.
Watering cannabis seedlings properly is the hardest part for beginner growers, watering too much can result in an overwatered cannabis plant, and watering too little can result in an underwatered weed plant so make sure you start watering with around 100 ml and increase the amount according to how your plants grow.
Seeds were planted too deep
1 – 3 cm is the deepest you should go in order to provide support to the roots and cover the seeds with the substrate. If you plant the seeds too deep the seedling could have a hard time sprouting out of the substrate so do not plant it too deeply.
Environment is not warm enough
Seedlings prefer warmer temperatures ranging from 22 -26 celsius and will grow at a slower rate in colder temperatures.
Environment is too humid
It’s recommended to use a plastic dome for newly born seedlings but remember to remove them as soon as the seedling starts developing the first pair of one-fingered leaves after the cotyledons as a high humidity can cause damping off, which results in seedlings folding over and dying.
Marijuana light burn can indeed hurt your plants if the light is too strong. Seedlings are more fragile than adult weed plants so make sure you dim down the light or adjust the fixture’s light to avoid stressing them. Also, if your seedlings are stretching a lot it means they need more light so, if this happens, increase light intensity or place the light fixture closer.
9. FAQs About Cannabis Seedling problems
Here are the most frequently asked questions about cannabis seedling problems to help you understand a bit more and help you deal with them. Just remember that different problems may have similar symptoms so make sure you are 100% sure about what the problem is before taking drastic measures.
“Why are my seedling’s leaves turning yellow? Could it be a cannabis nutrient deficiency?”
When the leaves start yellowing it’s probably a sign of nutrient problems, this means they’re either lacking nutrients, are getting too many nutrients or getting the wrong type of nutrients.
“When should I remove the plastic dome of the seedlings?”
The plastic dome helps raise humidity for faster germination so you can remove it as soon as your plant has completely developed a pair of leaves (after the cotyledons).
Remove the plastic dome once the seedling has developed the first pair of leaves after the cotyledons.
“Why are my cannabis seedling’s leaves curling down?”
This usually happens when you overwater your seedlings or when they’re exposed to higher temperatures so make sure the temperature ranges from 20 – 25 ºC and pay attention to how much water you’re watering with.
“When is it safe to put my cannabis seedlings under the light?”
Well, your seedling needs to be under light since germination but you can use a 15-20 W fluorescent light during the first 1-2 weeks and once the first pair of true leaves have completely developed, you can go ahead and place it under the LED or MH bulb.
“Is there a better light schedule for marijuana seedlings?”
The best light cycle for both autoflowering and photoperiod cannabis seedlings would be 18/6 from seed.
“Is the substrate super important for seedlings?”
Of course, the substrate mix is super important for a healthy start. Some growers prefer a “light mix” which can provide nutrients for the initial weeks and others make their own blends with perlite and coco fiber. There’s no best substrate but a substrate mix that allows for good oxygenation and water retention is ideal.
“Why are my marijuana seedlings growing so slow?”
This is the hardest question because it can be caused by several things. Your cannabis seedlings may be lacking nutrients or it could be caused by lack of proper lighting and extreme temperatures or humidity.”
“How far should the grow light be from the cannabis seedling?”
If you’re using a CFL light, the lights should be 5 – 10 cm from the seedlings. If you’re using HPS or MH, the light should be around 25 – 40 cm from the seedlings and if you’re using LEDs, the fixture should be at around 75 cm from the seedling with 40% light intensity if possible.
“How long does it take for the seeds to germinate and the seedling to come out of the soil?”
The germination process is usually quite fast but depending on the quality of the seeds, it may take up to 5 days or even more. Once the seeds have germinated and been planted in the pot, the seedling should take around 3 days to come out of the soil if the growing conditions are proper.
“Is it possible to know my plant’s sex during the seedling stage?”
No, you’ll only be able to tell whether your marijuana plant is a male or female during the pre-flowering stage. This happens because cannabis plants need to sexually mature in order to show either male pollen sacs or female stigmas.
10. In conclusion
Marijuana seedlings are super fragile and sensitive so you should take good care of them, avoiding cannabis growing problems at this stage is vital because even though your baby plants may recover, the size and structure may be affected, which will end up affecting your harvest.
If you have tips you can share with fellow growers to help them take care of their baby plants, feel free to leave a comment in the comment section below!
Now that your marijuana seeds have sprouted, what’s next? How do you care for your little baby marijuana seedlings? Your germinated seeds must be placed in a more suitable growing medium if you have started them in paper towels, rock wool or peat pellets.
- Small planters utilize your space better
- Small planters grouped together are the most efficient way to use your grow light source
- A small container keeps the roots together and is easier to feed and water.
Planting your marijuana seedlings
Place garden soil in your container up to about 1” from the top. Pack l ightly . Make a hole with a pencil, eraser-side down about ½” deep and put in your germinated seeds, root side down and cover with soil. If your seedlings are already in a seed-starter of some sort, simply bury them in the dirt and cover with ¼ to ½” of soil. Water until the soil is damp, not soaking. It is not necessary, but some marijuana growers like to give the young plants some support. Long wooden kitchen matches (minus the head) work well.
Watering and feeding your seedlings
During this phase, feeding or the adding of nutrients or fertilizer will not be necessary unless you have chosen a soilless mix. Watering should be done perhaps twice per day with a misting bottle for the first few days. How often you water will depend greatly on temperature and humidity. Once the marijuana root is better established, you can slowly cut back to watering every 2-3 days. If you are not sure, you can test by placing your finger into the soil. If it feels dry, then add water. It is important to note that the number one cause of early crop failure is overwatering. Wilting or drooping leaves on your plants are a sign that your plant is thirsty. Plants will revive quickly from such dehydration. While many gardeners use tap or well water, the more sophisticated growers use reverse osmosis, filtered or bottled water and adjust the pH (acidity/alkalinity) of the water. If you are using municipal tap water, fill a bucket or a reserve reservoir and let it sit for several days. This allows most of the chlorine present in the water to evaporate. DO NOT water directly on the plant. They are very delicate at this stage and the stem and roots are easily damaged. Water around the seedlings a few inches base of the plant. It is best to water your plants first thing in the morning for best uptake.
Marijuana seedlings lights
Marijuana seedlings require very little light and can be grown under CFLs (spiral compact fluorescents), tube fluorescents, LEDs and the blue light from Metal Halides (MH). Stay away from incandescent lights as they put off too much heat and too little light. The higher the Wattage your light source, the further away it should be from your seedlings unless you are using LED grow lights with good ones running nearly cold. Too far away and the plants will stretch towards the light making them weak and spindly. Too close and the bright light and heat may damage them, except with LEDs. Let us say you are using fluorescents or LED grow lights. It would be fine to place the light a foot above your plants to start and give the seedlings a chance to ‘harden up’. If they react favorably, you may lower the light a little bit each day until the lights are maybe 4” above your plants. Blue light dominant LEDs and full spectrum LED grow lights offer an excellent start, lower electricity costs and very little if any heat. High Pressure Sodium (HPS) lights are generally not used for seedlings as they do not require the amount of light that HPS puts out, and more importantly, HPS is deficient in blue light. Blue light is what plants use to point them towards the light source. This is called phototropism. Have fun and good luck growing out your marijuana seedlings!