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! Knowing where your cannabis plants are in their life cycle will dictate when to prune, train, and harvest your plants. Learn more about marijuana growth stages today. Everything you need to know about the 6 stages of cannabis growth. From selecting seeds to determining plant sex.
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!
4 stages of marijuana plant growth
Cannabis plants go through a series of stages as they grow and mature, and those different growth stages call for different amounts of light, nutrients, and water.
It’s important to know these stages and how long each lasts to know what the plant needs and when. Knowing where your cannabis plants are in their life cycles will dictate when to prune, train, and trellis your plants, and when to harvest.
How long does it take to grow a marijuana plant?
Generally speaking, it takes anywhere from 10-32 weeks, or about 3-8 months, to grow a weed plant from seed to harvest. It’ll be quicker if you start with a clone or an autoflower seed.
The biggest variability in how long a marijuana plant takes to grow will happen in the vegetative stage—after the seedling phase and before flowering.
If you’re growing indoors, you can force a weed plant to flower after only a few weeks when it’s small or after several weeks when it’s big.
When growing outdoors, you’re at the whim of the seasons and will have to wait until the sun starts to go down in the fall for plants to flower, and then to harvest.
However, one way outdoor growers can control the flowering cycle is by using light deprivation techniques.
What are a weed plant’s growth stages?
The growth stages of marijuana can be broken down into four primary stages from seed to harvest:
- Germination (3-10 days)
- Seedling (2-3 weeks)
- Vegetative (3-16 weeks)
- Flowering (8-11 weeks)
Cannabis seed germination
Seed germination length: 3-10 days
Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors
The first marijuana plant stage begins with the seed. A cannabis seed should feel hard and dry, and be light- to dark-brown in color. An undeveloped seed is generally squishy and green or white in color and likely won’t germinate.
Once your seed has germinated, or sprouted, it’s ready to be placed in a growing medium, like soil. The tap root will drive down while the stem of the seedling will grow upward.
Two rounded cotyledon leaves will grow out from the stem as the plant unfolds from the protective casing of the seed. These initial leaves are responsible for taking in sunlight so the plant can grow healthy and stable.
As roots develop, the stalk will rise and you’ll begin to see the first iconic fan leaves grow, at which point your cannabis plant can be considered a seedling.
Can you speed up the germination process?
No. Cannabis seeds are delicate and don’t like to be moved around. They need a warm environment that doesn’t fluctuate in temperature, and not too much water. Once you put them in soil, we recommend leaving them be.
Quality seeds typically have high germination rates, but you may get some duds that don’t sprout. Let them do their thing; helping them along can decrease their change of survival.
Seedling stage in cannabis plants
Seedling stage length: 2-3 weeks
Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors
When your marijuana plant becomes a seedling, you’ll notice it developing the traditional cannabis fan leaves. As a sprout, the seed will initially produce leaves with only one ridged blade.
Once new growth develops, the leaves will develop more blades, or “fingers” (3, 5, 7, etc.). A mature cannabis plant will have between 5 or 7 blades per leaf, but some plants may have more.
Cannabis plants are considered seedlings until they begin to develop leaves with the full number of blades on new fan leaves. A healthy seedling should be a vibrant green color.
Be careful to not overwater the plant in its seedling stage—its roots are so small, it doesn’t need much water to thrive.
At this stage, the plant is vulnerable to disease and mold. Keep its environment clean and monitor excess moisture. Be sure to give it plenty of light.
Even if growing outdoors, a lot of growers will start their seeds inside under an artificial light to help them through this delicate stage of marijuana growth.
If you buy a clone from a grower or breeder it will be a seedling, so you can skip the seed germination phase.
Vegetative stage in cannabis plants
Vegetative stage length: 3-16 weeks
Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors
The vegetative stage of cannabis is where the plant’s growth truly takes off, and it typically lasts 3-16 weeks. At this point, you’ve transplanted your plant into a larger pot and the roots and foliage are developing rapidly. This is also the time to begin topping or training your plants.
Be mindful to increase your watering as the plant develops. When it’s young, your plant will need water close to the stalk, but as it grows the roots will also grow outward, so start watering further away from the stalk in the soil so roots can stretch out and absorb water more efficiently.
Vegetative plants appreciate healthy soil with nutrients. Feed them with a high level of nitrogen at this stage.
Cannabis plant flowering stage
Flowering stage length: 8-11 weeks
Marijuana light cycle: 12 hours a day indoors; full, direct sun 6 hours a day outdoors
The flowering stage is the final stage of growth for a cannabis plant. This is when plants start to develop resinous buds and your hard work will be realized. Most strains flower in 8-9 weeks, but some can take even longer, especially some sativas.
Outdoors, flowering occurs naturally when the plant receives less light each day as summer turns into fall.
Indoor growers can trigger the flowering cycle by reducing the amount of light marijuana plants receive from 18 to 12 hours a day.
There are three subphases of the flowering stage:
- Flower initiation (week 1-3): The plant will continue to grow and females will develop pre-flowers—pistils, or white hairs, will grow out, which are the beginnings of buds.
- Mid-flowering (week 4-5): The plant itself will stop growing and buds will start fattening up.
- Late flowering/ripening (week 6 and on): Trichome density will increase and plants will get very sticky; keep an eye on the color of the pistils to tell when to harvest.
There are a number of changes to consider once plants go from the vegetative stage to the flowering stage:
- Don’t prune when plants are flowering, as it can upset their hormones
- Plants should be trellised or scrogged so buds will be supported as they develop and air can flow through plants
- Consider giving plants bloom or phosphorus nutrients
What does the pre-flower stage look like?
Pre-flowers are the beginnings of cannabis plant sex organs. If you’re growing regular seeds, you’ll likely have a mix of male and female plants and will need to determine the sex of your plants to discard the males. It’s imperative to separate males so they don’t pollinate the females.
Pre-flowers appear at the nodes of the plant, where a branch grows out of the main stalk. Females will develop an oval-shaped bract with hairs or pistils sticking out, while males will develop round pollen sacs.
Learn more about pre-flowers and cannabis plant sexing in our anatomy article.
How to tell when a cannabis plant is ready to bloom
When growing outdoors, weed plants will start flowering, or blooming, after the summer solstice, when the daily amount of light starts to decrease. Plants will start developing pre-flowers, as mentioned above, telling you that flowering has initiated.
When growing indoors, growers make the decision to force blooming or “flip” plants into flower by cutting off the amount of artificial light they receive.
What to do when cannabis plants flower early or late
The amount of time it takes a plant to finish, or be done flowering and ready for harvest, will depend on what strain it is. Typically, indicas finish flowering early and sativas finish flowering late.
Note information from the breeder when you buy seeds to grow to get a sense of how long it takes to flower. You may have to harvest some plants early and some late depending on their finish times.
For late-flowering strains, keep an eye on the weather and make sure cold weather doesn’t ruin your plants before they finish.
When do buds grow the most?
Buds typically grow the most toward the end of the flowering life cycle. You probably won’t notice much budding out at the beginning of the flowering stage, and it will slow down toward the end of the cycle, when buds become fully formed.
Once buds have reached full maturation, it’s time to harvest your marijuana. How long it takes to harvest buds depends on many factors, including harvesting methods and how many plants you harvest.
How long can a marijuana plant live?
Weed plants are annuals, meaning they grow and live for one season and then die. Wild cannabis plants grow seeds and drop them when they die, which will grow into new plants the following year.
When harvesting, plants are cut down and die in order to get their buds. New seeds need to be planted in order to grow more plants.
If left unharvested, weed plants will eventually wither and rot within a few months after the peak flowering phase.
When should you grow marijuana?
If you’re growing outdoors in the Northern Hemisphere, growers usually get their seeds between February and April and start germinating seeds by the end of April.
Many start growing seedlings inside in a more controlled environment because seedlings are more delicate, and then put the seedlings in the ground outside once they’re a little bigger and the weather is warmer.
If you’re growing clones or autoflowers, you have a grace period of another month or so. Plants usually need to be outside, in the ground, by the end of June.
Harvesting happens sometime between September and November. This depends on your local climate, as well as the weather that particular year—one year it could be the end of September, the next, end of October; growers in the Pacific Northwest will have to pull down their crops earlier than those in Northern California because of cold weather.
If you’re growing weed indoors, you can grow whenever you like. Keep in mind that the outside environment will affect your grow space—you may need to add heaters in the winter or fans and ACs in the summer.
Other than that, you can start seeds whenever you like and flip them into flower whenever you like, depending on how big you want the plants.
Important dates for growing marijuana outdoors
Many growers begin germinating seeds as early as February and March in order to have big plants come harvest time, but the Spring Equinox is a good reminder that it’s time to kick off the outdoor growing process and start germinating your seeds if you haven’t already.
Many farmers wait until after Mother’s Day in May to put their plants outside. Just make sure all of your plants are outside by the Summer Solstice at the latest.
The weather will start to turn and the sun will begin descending in the sky as your plants fatten up with sweet, sticky buds. It might be tempting, but the Fall Equinox is about when to start harvesting. It’ll depends on your climate and the year—it could happen a little before or after.
Everything should be cleaned up, dried, and curing by Thanksgiving, and in some places, even by Halloween.
As winter approaches, it’s prime time to make your own cannabutter, topicals, or tinctures with all that trim from the harvest. Kick your feet up, relax, and hunker down for the cold, it’s been a long growing season!
Notes on marijuana growth phases
We can’t stress enough that the timeframes in the above graphic are ranges of time for the Northern Hemisphere. You’ll need to adjust them based on your specific region and local weather and climate.
Be sure to keep a grow journal to track the progress of your plants. Looking back on your notes will help you learn from mistakes and maximize the quality and quantity of your buds next year.
Take meticulous notes on when and how you perform each step, noting:
- How much water you give plants, and at what intervals
- Nutrient amounts
- When you top and prune
Pictures will also give you a better sense of how your plants look along the way.
The Stages of Cannabis Growth
Cannabis growth is made up of a series of stages that plants undergo during their lifecycle. Each stage during the cannabis cultivation process requires its own unique demands, including different levels of light, water, and nutrients.
It can take anywhere from 4 to 8 months to grow a cannabis plant, this varies based on where you’re growing. If you have an indoor grow room, your plant has the ability to flower after only a few weeks!
The quality of your plant depends on your knowledge of the cannabis growth stages and the lifecycle of your plants.
Cannabis Growth Timeline
1. Germinating: 1-7 days
2. Seedling: 2-3 weeks
3. Vegetative: 2-8 weeks
4. Pre-Flowering: 1-2 weeks
5. Flowering: 6-8 weeks
1. Germinating Seeds
2. Seedling Stage
3. Vegetative Growth
How to tell if your plant is a male or female
Female: Two pistils (the pistil contains the reproductive parts of a flower) will be growing on the buds (flowers grow above these leaves, one cluster on each side).
Male: Small green sacs full of pollen will be seen on the node areas.
- If there is a high color ratio of white to red pistils your cannabis will provide a euphoric THC high.
- If the color ratio is more red to white, your cannabis will provide a calmer, CBD-stoned feeling.
- If you harvest once half the trichomes are opaque and the pistils haven’t turned brown, your cannabis will provide a balanced THC/CBD high.
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