3 Week Old Weed Plant From Seed

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! The germinated seeds peak out above ground and immediately spring up into small, blade-like green plants. Here's what to expect for weeks 2 and 3 of your cannabis grow. Let's talk about your cannabis sprouts and what they will require to stay strong and healthy.

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.

2. Overwatering

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.

3. Underwatering

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
Medium pH PPM
Soil 6.0-7.0 100-250
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.

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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 Properly

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.

Light Intensity

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.

See also  Colorado Weed Seeds

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!

How To Grow Weed During The Vegetative Phase

How to support cannabis during the vegetative stage for best results.


  • 1. What is the vegetative phase?
  • 2. Importance of the vegetative phase
  • 3. How to achieve ideal vegetative growth
  • 4. Giving your cannabis seeds the best start
  • 5. The first two weeks of the vegetative phase
  • 6. Other factors to consider during the vegetative phase
  • 1. What is the vegetative phase?
  • 2. Importance of the vegetative phase
  • 3. How to achieve ideal vegetative growth
  • 4. Giving your cannabis seeds the best start
  • 5. The first two weeks of the vegetative phase
  • 6. Other factors to consider during the vegetative phase


The vegetative phase is a period of the growing cycle that takes place after germination and before flowering.

After your cannabis seeds germinate, they’ll emerge from the soil as seedlings. These youngsters feature a short stem and two rounded cotyledons. Eventually, the first “true” leaves will form. Over the subsequent 2–3 weeks, seedlings will start to mature and produce a large number of fan leaves—structures required for photosynthesis. This marks the beginning of the vegetative phase.

The vegetative phase can last anywhere between 3–16 weeks (or longer), depending on the genetics of a cultivar and the goals of the grower. Explosive growth occurs during this time. Plants are typically transplanted into larger containers at the start of the vegetative phase to give their root system more room to expand. The main stem will ascend, and the space between nodes will increase dramatically. Indica cultivars will remain short and put out lots of lateral growth, whereas sativa varieties grow taller with much less ramification.For photoperiod varieties, the vegetative phase ends when the light cycle shortens.

  • Outdoors, this happens as the seasons change from summer to autumn.
  • Indoors, the lighting schedule is shortened to force photoperiod plants to flower on command. Plants will transition from the vegetative phase into bloom when exposed to a light cycle of 12 hours on and 12 hours off. In contrast, autoflowering cultivars initiate flowering based on their age as opposed to light cycle.
Growth phase (Week 1) Growth phase (Week 2) Growth phase (Week 3) Growth phase (Week 4)
Growth phase (Week 5) Growth phase (Week 6) Growth phase (Week 7) Growth phase (Week 8)


The vegetative phase is a vital period in the life cycle of a cannabis plant. Growers need to provide optimal environmental conditions for their plants to grow as large and healthy as possible. Size often equates to yield. The bigger plants become, the more nodes or “bud sites” they develop, and the more flowers they’ll be able to produce. But size isn’t the only factor.

Some growers prefer to keep their plants small while still achieving excellent yields, which can be done by training plants. These techniques need to be implemented in the vegetative stage before the first flowers begin to emerge. Many essential physiological functions are underway during the vegetative stage. Fan leaves are working hard to convert light and CO₂ into energy. The root system is expanding and providing a firm anchor to prevent the plant from toppling over; the roots also work to uptake vital nutrients and water. To meet the demands of plants during this time, growers need to ensure they provide the correct amount of light, water, and nutrients.

Cultivators also need to be aware of pests and pathogens, and do their best to prevent these threats from damaging or even killing their crop. Ultimately, the vegetative period sets the stage for flowering. The healthier plants are during this time, the more prepared they will be for flowering and a bountiful harvest.


The factors mentioned above apply to every cannabis grow. When cultivators manage to strike the perfect balance between all of these variables, remarkable growth becomes possible during the vegetative phase. Although the primary demands of plants remain the same, growers need to be aware of the differences between growing indoors and outdoors. These two very different environments present growers and their crop with various challenges.


Growing indoors usually involves raising plants in grow tents or dedicated grow rooms—this comes with distinct advantages and disadvantages. Indoor growers have almost complete control over the environment during the entire duration of the growing cycle. During the vegetative phase, they can elect to run lights for 18–24 hours per day. The more light a plant is exposed to, the more it can photosynthesise, resulting in more explosive vegetative growth. More control means there’s also more to manage. Indoor growers need to measure CO₂ levels, humidity, and temperature regularly. These factors need to be kept within specific parameters to optimise plant growth. Growers may need to invest in fans, hygrometers, humidifiers/dehumidifiers, extractor fans, and more to keep their operation running smoothly. These systems can be automated using timers and sensors, but this isn’t realistic for amateur and hobbyist cultivators.

Vaping boasts the same speed of onset as smoking. However, these devices use lower temperatures and expose users to fewer toxins.


Outdoor growers have much less control over their plants during the vegetative phase and the growing cycle as a whole. The elements take control, which can be a good thing in some circumstances. You don’t have to provide a light source, and frequent rain and irrigation systems remove the need to water regularly. Achieving ideal vegetative growth outdoors mostly lies in boosting your plants’ defences. There are a lot of critters out there that will happily chow down on your plants for lunch. Small creatures such as insects can burrow into leaves and munch into roots, whereas animals such as birds and deer can do some severe damage to leaves and stems. Humid environments also increase the risk of fungal infections. Biological controls such as predatory insects can be introduced to the garden to eliminate pest species, and companion plants can be grown to deter them. Netting and fencing are an effective line of defence against larger animals. Foliar sprays can help to keep mould away. Growers should also place their crop in an area of the garden that receives good airflow, and avoid stagnant areas.

Caring for your Cannabis Sprouts – Growing Weed Week 2 & 3

When we last left off, we had three seeds in party cup planters inside our space bucket. The taproot of that seed is attempting to drive its way down through the soil and start developing its first roots. While the taproot is traveling down to find more water, the other half of that germinated seed will start looking for sunlight. The first set of leaves you will see are called the cotyledons. These baby leaves were tucked into that seed before and will now start collecting energy through photosynthesis.

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See also  How To Grow Weeds From Seeds Hydroponic System

Here’s the sprout in a humidity tent (sandwich bag). This helps keep the sprout in a humid environment and prevents the soil from drying out too fast.

A happy cannabis sprout will grow low to the soil. Keep the soil moist, not wet. Don’t let the soild dry out either! This is 1 week after I planted the seed

Week 2

Now that the seed is sprouted, it is very fragile. It will need to be in an environment that is humid and warm. You’ll want to keep these sprouted seeds in a temperature range between 20 and 29 degrees Celsius. The humidity should be about 70%. If you’re having trouble maintaining this humidity around your sprout. place a sandwich bag (with a few holes for airflow) over the planter. This keeps moisture in the soil from evaporating too quickly.
Growth will look like it’s slow at first, but in the soil, there’s plenty of action. That sprout is spreading it’s root system quickly to help support growth later on.
This sprout stage will last a few weeks. You will notice that early sets of leaves won’t look like your typical cannabis leaves, this is normal. By the third and fourth set of leaves, it will start looking like your typical cannabis plant, these are called the true leaves.

How Big Should My Weed Plants be After 2 Weeks?

In most cases your plant should be around 2 to 3 inches tall with 2 to 3 sets of leaves including the cotyledons (seed leaves which are rounded). Results may vary bu t it would greatly depend on the quality of your seeds, the soil you’re germinating in and the quality of the light they’re receiving.

If your sprout isn’t getting enough light it might begin to stretch tall in an attempt to get closer to a light source. If your using a light but the seedling is still stretching you might be using the wrong type of light. Use a light source that has some blue in it, “cool white” bulbs are good for seedlings for this reason. There are professional grow lights for seedling as well.

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Do I need to start giving my plants fertilizer now?

The most important thing for a small cannabis sprout right now is the time to develop a strong root system. That’s why our Reefertilizer cannabis grow system includes our Start soil conditioner.
This organic soil amendment is made from brown sea kelp and contains mycorrhizal spores.

Mycorrhizal spores are a type of fungus that grows symbiotically with plant roots helping improve their ability to take on water and nutrients. The organic sea kelp is full of beneficial micronutrients that help feed small plants without burning them.

Once the plant has been put in a larger pot and has 4 to 5 sets of leaves you can begin using Reefertilizer Grow for the vegetative stage.

Uh Oh, Your Cannabis Seeds Didn’t Sprout

It’s not a big deal, sometimes it happens to the best of us. In my case only two of the three seeds took root. There are several reasons a seed might not turn into a sprout.

Too wet, or too dry

If your soil medium gets to dry, it will damage the sensitive hairs that cover the taproot. If the soil is too wet, the taproot will drown. You want to keep the soil moist, not dry and not soaking wet. Giving the soil a nice misting of pH 6-6.5 water every few days should be enough.

Too cold, or too hot

Extreme temperatures will definitely harm you cannabis sprout. Keep the temperature between 20 and 29 degrees Celsius. Anything outside that range is risky.

Planting too deep, or too shallow

If you plant your seeds too deep, they won’t have enough strength to reach the surface of the soil and start photosynthesis. If the seed is planted too shallow, it will potentially dry out and die. The best depth to plant a seed is at 1/2″ or 1.25cm.

Bad seeds or genetics

Some seeds just aren’t viable. If a seed isn’t stored correctly, its quality will be compromised. Fresh seeds from a reputable supplier are usually the best seeds in my experience.

Week 3

Your sprout should be growing a little bit each day. This growth will get faster and faster until you will have to transplant it into a larger planter. This early stage from germination to the beginning of veg will take 3-4 weeks.

Keep your soil moist and avoid overwatering or letting your plant dry out.

Through week 3 we will continue to monitor our seedlings as they grow. You will also want to make sure air is circulating around this sprout. A small usb fan is perfect for this.

Feeding Cannabis Sprouts

The soil mix we used already contains nutrients. The potting soil, worm casting, and Reefertilizer Start all contain nutrients that your young seedling will slowly feed off of. Also, the seed itself contains nutrients that will help get it started. Because of these factors, you won’t need to start feeding your plants until the first few sets of true leaves form around week 3 or 4. When you do start feeding you will be starting with a light dose of nutrients. You would start with 5ml (1 scoop) of Reefertilizer Grow mixed into 4L of water. If 4L is too much then you can just divide by two or four. So 2.5ml for every 2L of water. Our feeding calculator can help you find out the correct measurement.

Things to watch out for in week 2-3 of growing cannabis


Your plant is still in its baby phase, and it can only take so much water. You might feel like watering it every day will help it grow faster, when in fact you’re hurting your plant. Your plant’s roots need water as well as air, and if your soil is always soaking wet your roots will drown. Keep the soil moist by misting it with a spray bottle. When you have a humidity bag (sandwich bag) over the planter, you probably will only need to mist your plants once, maybe twice a week.

Give them light

Your cannabis sprouts will need a minimum of 16 hours of light a day. The distance between the light and your sprout also matters. I’m using a LED grow light so I’ll be maintaining a distance of around 12 inches. If you’re using CFL light (fluorescent) they will need to be much closer (2-3 inches). Your sprout will tell you if it’s getting enough light by growing short and fast. If the sprout is stretching, it means the light is too far and the plant is stretching to get closer. Stretched sprouts can easily be fixed by transplanting them into a larger planter and covering the elongated stem in soil.