Cannabis Seed Sprouted But Stopped Growing

Cannabis seedling problems can be easily remedied or avoided from the start. Learn how to diagnose and resolve cannabis seedling issues! Common Seedling Problems & Mistakes Before we take a look at cannabis seedling problems and common beginner mistakes, let’s show you what healthy cannabis seedlings and young plants look like! If

Cannabis Seedling Problems: How to Resolve Any Issues

From seedling stuck in shell to stunted growth to yellowing to various stresses – we’ve tried to cover it all

Twisted leaves point to some kind of mutation. This palnt can still be brought all the way to harvest, but it’s not the genetics that you’d want to keep.

Newbie growers tend to run into cannabis seedling problems with their plants from day one. That’s why our diagnosis tool can come handy to you. Start by finding your cannabis seedling issues in the list below (we tried to group them for more convenient navigation), and then use page jumps (or scroll down) for possible causes and solutions.

It may be a serious disease, or just a temporary issue that is easy to fix, or even a perfectly normal thing that you mistook for a sign of trouble. In the latter case, we recommend you to read our article on the anatomy, development and look of a healthy seedling. And, of course, it’s better to ensure that no cannabis seedling problems arise in the first place, so we encourage you to read another article with tips on creating perfect conditions for your sprouts and caring for them the right way.

Symptom Possible Cause/Remedy
weed seedling won’t shed shell see Removing the ‘Helmet Head’ by Hand
weed seedling not opening see Removing the ‘Helmet Head’ by Hand
or
The Problem of Weed Seedling Damping Off and Other Root Problems
marijuana seedling too tall
weak/thin stem
seedling bending/falling over
see Seedling Stretching: Reasons and Solutions
cannabis seedlings keep dying
seedling sprouted but not growing
seedlings not growing true leaves
see The Problem of Weed Seedling Damping Off and Other Root Problems
cannabis seedling very short see The Problem of Weed Seedling Damping Off and Other Root Problems
or The Seedling Gets Too Much Light
weed seedling limp see Water Stress (Overwatering / Underwatering)
or The Problem of Weed Seedling Damping Off and Other Root Problems
leaves light green and going yellow
marijuana seedling leaf tips turning brown
see Cannabis Seedling Problems with Nutrients
marijuana seedling turning yellow see The Seedling Gets Too Much Light
leaves turning white / bleaching see The Seedling Gets Too Much Light
or Cannabis Seedling Problems with Nutrients
yellow veins or seedlings yellow in middle
white / red / purple / brown stem
purple leaves/veins
see Discoloration Isn’t Always a Sign of Trouble
marijuana seedling dark green see Cannabis Seedling Problems with Nutrients
leaves pointing up
seedling cupping/praying
leaf edges curling up
see Heat Stress is Common Among Cannabis Seedling Problems
leaves pointing/curling down see Water Stress (Overwatering / Underwatering)
or Wind Burn
wavy leaves see Water Stress (Overwatering / Underwatering)
deformed/twisted leaves see Weed Seedling Mutations
cannabis seedlings eaten / uprooted / broken etc. see Physical Damage: When a Seedling Can and Cannot be Saved?

Table of Contents

Removing the ‘Helmet Head’ by Hand

Too often, when a weed seedling is sprouting from the medium, the cotyledons are still stuck in the shell and it won’t come off on its own.

This is day 1 for three OG Kush Auto seedlings. Only one of them has cast off its shell on its own.

Probably, most seedlings will find enough strength to eventually shed the shell, but meanwhile a lot of time will be lost and you’ll see a lot of stretching. So you have to remove the shell yourself as soon as possible. Moisture is the key here. If the seedling is still tiny and can be covered by moist medium, by all means do so. Probably it will be enough. If not, the shell will be wet enough in a couple of hours, so that you can easily remove it with your fingers.

If the seedling is already too tall to be covered with wet soil, spray it with water or put a droplet of water on the shell: this will make it wet and mushy after a while. Then remove the shell with your fingers.

We’re wetting the shells with a drop of water. It will be enough to easily remove them from cotyledons.

Sometimes the shell comes off, but a thin membrane covering the cotyledons remains. Usually, it’s the reason why weed seedling is not opening. The membrane is too dry and acts as a straightjacket. Make it wet and when it gets soft, pluck it with your fingers. It usually slips off quite easily.

We have removed shells from the seedlings on the right and in the center. The one in the center still retains the membrane.

Warning: Sometimes, the seedling hasn’t rooted too deeply and has still a very short tap root (like an inch or so). In this case, the procedure described above can result in your plucking the sprout out of the soil completely. So never apply excessive force. It’s better to make the shell wet again and wait a bit more. If you did pull the sprout out of the ground, you can still stick it back in (probably, it’s best to remove the shell first). Most seedlings can survive this without apparent shock or stress.

In your future grows, make sure that sprouts emerge from the medium already without a shell. Keep the surface of the medium moist at all times, and you probably should think about placing the seed a little deeper than you did before. In this case, the seedling will encounter more resistance on its way up and the shell will slide off.

Seedling Stretching: Reasons and Solutions

Most seedlings are tall and skinny and look vulnerable, and generally it’s not a problem. But sometimes the stem is growing too tall, weak and thin and can’t support the weight of cotyledons anymore. As a result, the long stem is not growing straight, but sideways or even upside down. The reason is simple: there’s not enough light. Either the source is too weak (e.g. you keep your seedlings on the window sill), or the light is placed too high above. In either case, seedlings stretch toward light uncontrollably and keep falling over.

We still recommend that you play it safe the first couple of days and keep the light at a distance. Let the seedling reach the height of 2-3 inches (5-7 cm) – it’s normal and healthy and much better than the other way around: when the sprout is stressed by too much light (and sometimes heat). Slowly correct the distance before you see the seeding bending, leaning or even falling over. In time, you’ll know the exact distance for your type of bulb.

But what to do if a seedling already bent and flopped over? You can always use a toothpick to prop a weed seedling not standing up. However, it is best to make the stem that is too long shorter. You can do this by adding more soil (or coco, or other medium) – then the part of the stem that you cover by the medium will grow more roots, and it’s great. Or, if the container isn’t tall enough for that, you can press the seedling to the soil horizontally (it’s easy when the stem is already bent or the seedling fell over) and cover it with a thin layer of soil. If there’s too much resistance, gently crush the stem with your finger tips, probably just above the surface – it won’t really hurt the seedling.

This seedling has clearly stretched too much and needs to be made shorter. Strart by crushing its stem with your fingers just above the surface of the soil and then do the same in several places above.

Now that the stem is soft and pliable, lay it on the soil, probably in a half-ring shape.

Now cover the bent stem with soil and don’t forget to water. Note that this procedure will slow down the growth a bit, compared to seedlings that you didn’t let stretch in the first place.

The Problem of Weed Seedling Damping Off and Other Root Problems

Stunted growth, or slow growth, is common among cannabis seedling problems. The reason can be anything: from wrong conditions to stress to shock, but here we’ll talk about problems in the root zone. Healthy root growth is the single most important factor for a plant’s well-being, and if you see that your marijuana seedling stopped growing or is growing very slow, or especially if cannabis seedlings keep dying on you time after time, the first thing to check are the roots and what’s going on with them. Are they affected by some type of fungus? Is there root rot?

Most of the time, these problems arise when the medium is constantly wet and cool at the same time. These are ideal conditions for mold and fungi, and can lead to the weed seedling damping off. Apart from the seedling not growing leaves or its slow growth in general, you will notice that the stem gets very thin just above the surface. Next thing it will flop over. And, of course, you may notice some whitish substance on the surface of the soil. When the soil feels damp and cold to the touch, it happens very often. And the problems are not just on the surface, but more importantly deep down, too.

Cannabis Seedling Problems Can be Caused by Bugs

Another reason why a seedling has sprouted but is not growing is that some kind of bug living in the soil has eaten the tap root. You wonder why the seedling won’t grow without realizing that there is in fact nothing at all below the surface, no roots to speak of. This sprout will die, and there’s nothing you can do about it. To prevent this from happening in the future, kill all the parasites in the soil with heat. Just make the soil wet and place it into the oven at around 200° F (90-100° C) for a half hour or so.

A Root-Bound Seedling is Hardly Ever a Problem

Some novice growers wonder if a cannabis seedling can become root bound. It’s the situation when there is too little room in the medium, so that the roots reach the sides of the container and start to grow along them, simply because they have nowhere else to go. It’s quite a common situation for mature plants growing (or shall we say ‘not growing’?) in too small pots, but seedlings generally haven’t enough time for their roots to use up all available space. So seedling becoming root bound is hardly ever an issue.

And, of course, if you feel that your marijuana seedling is growing slow or not growing fast enough for you or is very short, make sure that you don’t expect too much. Read about the healthy and normal seedling development here.

The Seedling Gets Too Much Light

Most marijuana growers would swear that the more light the better. However, the issue of too much light is the real thing, especially for weed seedling. We have been sent countless pictures of seedlings showing the signs of stress from too much light. To be frank, we sometimes (erroneously) diagnosed the issue as potassium (K) deficiency which is often manifested by the lower leaves turning yellow at the edges. However, if you see this symptom in sprouts, the first thing you should suspect is that you have a source of light that is too intense or too close.

You may ask why then this symptom (yellow spots along the edges) appears not on the topmost leaves, but on the lower ones? Well, it’s because the lower leaves have had more exposure to the stressful levels of light (simply because they are older and have been around longer). Leaves yellowing due to too much light are very rare if you use CFL or T5 lights, but with HID (high intensity discharge) bulbs, like HPS or MH, or with the LED technology, these problems are very common.

Too Much Light and Heat Stress Often Go Hand in Hand

If you see seedling leaves turning white, sometimes to the point of complete bleaching, it also can be caused by too much light, but also made worse by heat stress (see below) and maybe calcium deficiency (these two often come hand in hand). Remember that for plants grown in coco calcium deficiency is especially common.

Another sign that your light is simply too much for this stage is that the seedling stays very short. It not only has no reason and motivation to stretch toward the bulb, but the dense flux of photons is constantly pounding on it, causing it to keep close to the ground.

If you see any of these signs, simply raise the lights, or use weaker ones.

This seedling was exposed to the harsh light of a LED bulb for too long. That’s why its cotyledons and the first pair of true leaves look yellow, dry, and brittle.

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Another severe case of too much light. Again the culprit is a LED bulb that was kept too close to the seedling.

These two plants stand next to each other under two CFLs each. There’s clearly something wrong with their lower leaves. Our guess is they have received too much light. See how compact and dense they are.

Cannabis Seedling Problems with Nutrients

When you see a yellow leaf on your seedling, it’s not necessarily the symptom of too much light (as described above). It can also be a nutrient deficiency. It is seldom the case in soil, because soil mixes come preloaded with fertilizers, organic or synthetic, and it’s enough for the first two weeks or so. But if you use some sterile medium like coco or rockwool, it’s your job to provide your seedlings with plant food. Unfortunately, it’s more than easy to make mistakes here.

This seedling looks yellow and sickly. Most probably, it suffers from many deficiencies, including N deficiency. Note that the medium here is coco. In soil, you can give your seedlings only plain water and still see no deficiencies whatsoever.

Read carefully the instructions for your nutrients formula and follow them, not forgetting to adjust the dosage for various stages. Look at the color of your seedling: its leaves should have a healthy and vibrant green color. If leaves are light green or yellowish or you see yellow cotyledons, it could be nitrogen (N) deficiency. Although sometimes, if you overwater your young plants for days and weeks, they can show the same symptom (but there will also be others, more specific; see below).

If the seedling is dark green, it looks more like N toxicity (too much nitrogen). In severe cases, seedling leaves will also be curling down.

If you see such deep, dark green color of the leaves, probably you’re feeding your plant too much nitrogen (N).

This is how nitrogen toxicity can look in a mature plant. Also check if it’s not a wind burn (if there isn’t a fan too close to the plant).

We already mentioned seedling bleaching and white spots while discussing the problem of excessive light, and mentioned that it could be caused or made worse by calcium deficiency, most common in coco.

And surely there is this widespread symptom of leaf tips turning brown which is a sign of nutrient burn. It simply means that the dosage of fertilizers that you give your plants when watering (or that is present in the soil mix) is way too high, and you should lower it when you see your seedling burn like this.

Discoloration Isn’t Always a Sign of Trouble

When you suspect that the color of your seedling is not quite normal, maybe you’re wrong. Of course, yellow hues should always raise a flag. The exception is when you look at a plant the first thing in the morning and see yellow in the middle of uppermost young leaves or yellow veins. It could simply mean that this is the new tissue that has grown in the dark and simply hasn’t had a chance yet to be filled with green chlorophyll. Expose it to light, and it’ll become green in no time.

Stem color can vary from plant to plant. It can be white, red, purple, and sometimes even brown. If there are no other worrying signs, it’s probably natural and caused by the specific genetics. Purple stem, veins, or whole leaves can also be due to colder night temperatures (in genetically predisposed strains). So when your seedling is turning purple, see if it doesn’t get too cold at night.

Heat Stress is Common Among Cannabis Seedling Problems

If your weed seedling experiences heat stress, it affects the shape of leaves in a very specific way. You may see the leaves pointing up.

Back in the day, we used to keep CFL bulbs too close to the seedling, and, instead of shying away from it, the seedling seemed to try and hug the bulb with its upper leaves. Other growers see it differently: to them it seems as if the seedling were praying. Still others name it ‘cupping’.

The underlying cause is the same though: not able to move away from the light, the seedling tries to position its leaves in such a way that the light falls on them only obliquely. This helps them absorb less heat energy. If you continue to expose your plants to heat (be it hot air, or the energy from the light), you’ll see a more sinister symptom: leaf edges curling up. The heat often aggravates calcium deficiency and vice versa.

To combat this problem, always try to maintain the correct temperature range in your grow room and make sure the light isn’t close enough to burn. The ‘backhand test’ can help you with that. Place your hand palm down under the light at the level of plant tops and hold it there for some time. If you feel the light ‘bite’ or there’s any discomfort, it’s best to raise the light.

If leaves on your cannabis plant (at any stage) curl up like this at the edges, it means they are overheated by light or hot air.

This young plant kept under a CFL has grown so fast overnight that it actually touched the bulb. Hence the burned leaves on top.

Water Stress (Overwatering / Underwatering)

Newbies overwater marijuana all the time. Luckily, the plants have a way of showing their caregivers that they overdo the watering. The first sign of overwatering is clawing of the leaves, of their curling down. When you touch the leaves on an overwatered plant, you’ll feel that they are quite rigid. Conversely, if the leaves are pointing down, but feel limp and lifeless, the seedling is probably underwatered.

Leaves on this seedling are shriveling up and curling down. The plant has clearly been overwatered. At the same time, it shows signs of heat stress.

Leaves can even change color because of water stress. If you keep them overwatered for long periods, they’ll begin to yellow and eventually die off. The bottom line is: when you see marijuana seedlings shriveling up, correct your watering schedule.

This chronically overwatered cannabis seedling has leaves that look yellowish and lifeless along the edges, almost as if they were touched by frost.

Sometimes, weed seedlings have wavy leaves. We don’t know the exact reason why it happens, but have this theory that the issue is due to irregular watering. No one has yet disproved this theory, and we continue observations. In any case, it’s not a grave symptom. Seedlings with wavy leaves may not look fit for a beauty contest, but are otherwise healthy and vigorous.

All of these seedlings have wavy leaves: a not uncommon symptom. Probably, at some earlier point, the grower has overwatered these plants.

Wind Burn

Another reason weed leaves can become deformed is when there is strong wind blowing on them all the time. For instance, you may have placed a fan close to a seedling, and it’s blowing straight at it and not above it. After a while, it may cause wind burn. Leaves that are stressed this way are pointing down and forming ‘claws’ similar to overwatering. But in this case, they also curl at the edges in the shape of tubes. Often, they also have dark green color, like they do when there is too much nitrogen in their feed.

Weed Seedling Mutations

Deformed, twisted, shriveled leaves – these symptoms can appear in marijuana seedlings for no reason and should be considered mutations. These plants are never the best specimens in terms of growing, but, if you bring them to harvest, the smoke may surprise you. It’s up to you to choose what to do with mutants. Seeds don’t come cheap, and you may decide to grow every one of them. That said, breeders always discard seedlings with leaves twisting, as well as with other mutations. There is one interesting mutation though that we personally wouldn’t mind to keep and propagate: weed seedlings with 3 leaves. Usually, leaves grow in pairs, opposite each other on the stem. But here you have three leaves growing from every node. Delightful!

Twisted leaves point to some kind of mutation. You can still succesfully bring this plant all the way to harvest, but it’s not the genetics that you’d want to keep.

A rare and cool-looking mutation: a cannabis plant with 3 leaves.

Physical Damage: When a Seedling Can and Cannot be Saved?

A special case of seedling problems is when a grower damages it by mishandling. A seedling can be knocked over and uprooted. If you don’t disturb the root system too much, the more vigorous sprouts can survive the repotting without even slowing down their growth.

Root damage is a bigger issue. It often happens during transplant when a piece of soil falls off, tearing off a part of the root ball in the process. You just put the rest back in soil, and hope for the best. When the root broke, it’s a significant stress for a seedling, so try to make its life for the next couple of days less stressful. You can do this by creating milder conditions, like light and temperature, and, of course, refrain from any major changes (repotting, switching to 12/12, or moving outdoors) until the damaged seedling resumes its growth.

And what if the stem broke? Partially broken stem can heal, no doubt about it. Just make a splint and put a bandage where the seedling snapped, and the tissue will not only heal, but even be stronger. Even if you break the stem clean off, it arguably can be made whole again in this way.

What you can’t do is make any use of a seedling that only consists of the roots and the stem, but no growing point, in other words no leaves, as when something has eaten them. The thing is that cannabis doesn’t grow from roots. There are simply no growing points there, so you can’t salvage such seedlings.

Say Goodbye to Cannabis Seedling Problems!

Most cannabis seedling problems can be resolved, and quite easily, too. Just don’t freeze with panic and use common sense. After all, there’s nothing magical about cannabis. It’s just a plant, and one that is quite hard to kill. And if you fail to save a particular seedling, learn not to repeat the same mistake next time.

Common Seedling Problems & Mistakes

Before we take a look at cannabis seedling problems and common beginner mistakes, let’s show you what healthy cannabis seedlings and young plants look like! If your plants look like this, you’re golden!

Healthy Cannabis Seedlings Look Like This!

Examples of healthy cannabis seedlings:

Cannabis seedlings start with two round leaves known as “cotyledons.” These leaves are already formed inside the seed and simply open up once the seed has sprouted. After the cotyledons emerge, the “true” (serrated) cannabis leaves will start to grow from the center.

As they get older, the leaves start looking more like the cannabis leaf you are probably most familiar with. Here’s what those seedlings look like as they start growing into healthy young cannabis plants…

Now that you know what healthy young cannabis plants look like; let’s take a look at some common seedling problems to avoid so your plants grow as fast and healthy as possible!

Common Cannabis Seedling Problems

1.) Overwatering

Symptoms: seedling is droopy, growing medium is moist, damping off

Most common causes:

When a cannabis plant is “overwatered” it has less to do with the water and more to do with oxygen. Plants can even grow directly in water (hydroponics) but in order to thrive, roots need oxygen. In hydroponics, that’s accomplished by dissolving oxygen into the water. But when plants are grown in a container, too much water = not enough oxygen.

When a plant’s roots are sitting in water, they quickly use up all the oxygen until the growing medium starts to dry out. Without enough oxygen at the roots, the plant will start showing symptoms of oxygen deprivation. Luckily, there are many steps you can take to prevent overwatering your cannabis plants.

While overwatering can display many different symptoms, most overwatered cannabis plants look droopy, like this…

Despite what seems like an obvious cause, several different scenraios can end in overwatering. Here are some of the most common trouble-makers:

Big Pot, Small Seedling

When you have a small plant in a very big pot, it’s easy to overwater because the roots aren’t drinking much yet, and the big container takes a long time to dry out.

Notice how the plants in smaller containers have grown more than the plant that was put in a big container as a seedling. It’s common for plants in too-big containers to grow a little slowly at first.

  • (Recommended) Start seedlings in smaller container until they’re growing vigorously, then transfer to a larger container
  • If seedling is already in a big container, there’s still hope! When watering, give just a little water at a time in a small circle around the seedling. Then allow the top inch of your medium to mostly dry before watering again. Once the plant is growing vigorously, start watering as normal (with extra runoff water coming out the bottom every time)
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These small cannabis plants (below) were put in big pots, and were given enough water to support a much larger plant. The plants couldn’t drink all the water that was given to them and as a result, their roots weren’t able to get the oxygen they needed and started “drowning.” Once the roots are out of commission, the leaves start drooping.

One way to prevent this from happening is to make sure your plants are in an appropriately sized container for each stage of their life; this is done with transplanting.

First, you need to get a general idea of the final container size which will be based on how big you want your plants to grow. The less often you transplant, the bigger the final size pot you’ll need because the roots will tend to grow out and cover the whole container if left too long. You can help avoid problems with roots getting rootbound by using a fabric pot (also known as a “Smart Pot”) or an air pot.

Final Container for Desired Plant Size – General guide
(the less often you transplant your plants, the bigger final size you’ll need)

12″ ~ 2-3 gallon container

24″ ~ 3-5 gallon container

36″ ~ 5-7 gallon container

48″ ~ 6-10 gallon container

60″ ~ 8-10+ gallon container

But what size pot should you use for your seedlings?

For fastest growth rates, it’s better to plant young seedlings or clones in a very small container, like a disposable plastic solo cup.

For new seedlings and clones, use a small container if possible

Easy transplant guide – some popular transplant guideline:

  • Solo cup -> 1 gal -> 3 gal
  • Solo cup -> 1 gal -> 5 gal
  • Solo cup -> 2 gal -> 5 gal
  • Solo cup -> 1.5 gal -> 3 gal -> 5+ gal

There is no perfect transplant guide, but the one above should give you a general idea of where to start.

Why don’t you want to go from a solo cup to a 5 gallon pot? Or why not just start in a 5 gallon pot?

Young plants won’t be growing very fast yet, so they also won’t be using much water. When you completely saturate a big container that slow speed means that the plant won’t be able to drink all the water. Since so much of the water is contained in the middle without access to air, it won’t be able to dry out by evaporation. This means you’re left with a huge container full of wet potting mix.

The young cannabis plant roots will quickly use up all the available oxygen that’s been dissolved in the water, and then the roots will sit in water until the water slowly evaporates on its own. Some containers such as smart pots and air pots allow air in from the sides, which can help dry the growing medium faster, but it’s better to use proper technique from the beginning.

Planting in too big a container is sometimes called “overpotting.” It’s possible to get around this with special watering techniques (for example by giving plants just a little bit of water until they start “growing into” their containers) but starting plants in small containers and transplanting as needed can be a more straightforward way for some growers. Overpotting plants is also a waste of growing medium and nutrients, especially if the plants never get big enough to fully use their containers.

This OG Tahoe Kush seedling was overpotted, though this can be overcome by the grower just giving a little bit of water at a time until the plant starts growing vigorously. At that point, the grower can provide more and more water until they’re finally watering normally.

More information about container size and transplanting here: https://www.growweedeasy.com/germinate#what-size-pot

Small Pot, Big Seedling

While using a too-large container can cause problems for seedlings, so can too-small of a container.

Seedlings are happy in a small container like a solo cup for a while, but as they get bigger, their roots need more room. The roots tend to wrap around the outsides of the container, encasing the middle part so that water can’t get out. This is known as the plant being “root bound.”

If the seedling isn’t transferred to a bigger container in time, it can cause symptoms of overwatering, nutrient deficiencies, wilting, and sometimes very strange and unpredictable symptoms.

These plants were left in a too-small container for too long. Because they were drinking so fast, the grower watered them frequently – too frequently! This combination of being root bound and overwatering caused the plants to suffer.

A too small container, combined with overwatering – these conditions can cause some strange symptoms that often look like a nutrient deficiency

Pink leaves, red discoloration, rusty spots and edges… While it make look like these cannabis seedlings are experiencing nutrient deficiencies, all these symptoms are actually caused by a combination of overwatering plus a too-small pot.

When the roots aren’t happy, the plant isn’t able to uptake nutrients properly and cannabis seedlings can show a wide variety of strange problems.

It’s usually not a good sign when cannabis leaves start “crossing their fingers” like this (instead of having all the leaf tips spread out). While this can happen naturally every once in a while, you know for sure that you’re having a problem if the crossed fingers are combined with discoloration of the leaves. Also notice how the stems are bright red/pink.

The following cannabis plant was also overwatered and had no drainage. Notice how dark the soil is and the green algae growing all along the top of the soil – these are more signs the plant has been overwatered for quite a while. You should never water your plant when the soil on top is still wet, and if you notice lots of algae growing on top of your soil, it may be a sign that you’re overwatering on a regular basis. Leaving the top of the soil wet is also the number one reason growers get fungus gnats.

No Drainage (or poor drainage)

Cannabis roots need oxygen to thrive, and therefore they will have trouble if the roots are “drowned.” If water cannot run out the bottom of the container, it will pool at the roots, which causes overwatered plants.

  • Always start with a good growing medium that drains well – never use a clay based soil which holds onto way too much water. A high quality potting mix (especially mixed with some perlite) provides great drainage
  • Start with a smaller container to reduce the chances of overwatering seedlings
  • Make sure there are plenty of drainage holes to let water out the bottom of the container
  • If water runs through growing medium slowly, you can mix perlite into the potting mix to increase oxygen and quicken drainage
  • Water less often and less at a time until plant is drinking more
  • Get a container that helps the growing medium dry out from the sides (such as “Smart Pots” – highly recommended; or air pots).
  • Don’t allow plants to sit in a tray that has been collecting runoff water

This seedling started “damping off” (dying) due to terrible drainage from bad soil. Never use soil that looks like it contains clay!

Seedling is “damping off” due to bad soil with no drainage

Here’s another example of a seedling damping off due to too much water (drowning roots), whis time combined with not enough light. After a few days of these conditions, this seedling just fell over and started dying.

The following plant was grown in an unsuitable growing medium with no drainage and started showing signs of overwatering. Always start with a quality potting mix that has good drainage, and never allow the top of your growing medium to look this wet!

This “soil” is more like mud. The plant roots are drowning from lack of oxygen, causing severe wilting.

Watering too often

While oxygen is available to the roots immediately after watering, the roots use up all the oxygen quickly if they are sitting in water. If all the oxygen is gone, roots are not able to get what they need to help power growth, at least not until the growing medium begins to dry out and create new air spaces in the growing medium.

Keep roots happy for fast-growing plants

Each air spot in the potting mix provides roots with precious oxygen, but if there’s no air spots, roots start to “drown.” By watering seedlings less often, growers can ensure that roots are getting access to plenty of oxygen at all times.

Of course you should never allow roots to actually dry out – roots need moisture at all times. But for new growers who want to do everything possible for their new seedlings, it can seem like more water = better. Unfortunately, this isn’t true.

Roots work best when they get as much oxygen as possible while also staying completely moist at all times.

  • Wait until top inch is dry. Make sure that the top bit of potting mix has started to dry before you water seedlings again. Sometimes it can take a few days, depending on your growing medium, your environment and how much water you provided during the last watering.
  • Increase the number of air pockets in the growing medium by mixing in a “lighter” amendment like perlite to the potting mix. Perlite will allow the mix to hold onto more oxygen when mixed with heavy soil. Many cannabis soil growers will mix 30-40% perlite into their potting mix to make sure there’s lots of drainage and plenty of air available for the roots.
  • Provide air from the sides. Transplant to a container which allows air in from the sides like fabric pots (“Smart Pots” – highly recommended) or air pots. until plant gets bigger so there’s less water in the potting mix that needs to dry. You’ll be able to water your plants more often while ensuring they get plenty of oxygen.
  • Water less when it’s cold. Plant processes tend to slow down when temps get cooler. This means that plants usually need water less often than normal after a cold snap.

This plant went through a few cool days but the grower continued to water as normal. As a result, the plants roots were surrounded by too much water and the plant started showing signs of overwatering.

The plant was watered the right amount each time, but too often. As a result, it shows some slight drooping. While this won’t kill the plant, the plant will definitely grow faster when the mix is allowed to dry out a bit so the roots are getting plenty of oxygen.

2.) Underwatering – seedling is droopy, wilting, or not growing properly, and the growing medium around the seedling isn’t moist

While overwatering is the most common seedling symptom, underwatering is also a problem, especially for those who have been warned to avoid giving too much water.

It can be confusing because the symptoms often look similar to each other, which is why it’s important to learn good watering practices.

This seedling was underwatered – the grower had been warned many times to avoid overwatering, and went too far in the other direction. Notice that the growing medium looks bone dry.

It’s crucially important to make sure that plant roots have access to moisture at all times. Plants are constantly losing water through their leaves (called “transpiration”) and this is actually how plants get water up from the roots. As the plants lose water from the leaves, it pulls water up from the ground like a straw.

When there’s not enough water at the roots, many plant processes cease to function. If roots actually dry out, the dried shoots die.

Here’s another example of a young cannabis plant that is underwatered, even in a big container (where the problem is usually overwatering). Notice how this cannabis seedling is basically just wilting and falling over, while the potting mix looks completely dry.

Seedlings suffer greatly from being underwatered, even more so than from overwatering. Often the grower will actually be able to see how dry the growing medium is. A big sign that the plant is being under-watered is when you can see the soil separating from the container. In this case, you can see the starter cube separating from the soil because it’s so dry.

Underwatering is bad on it’s own, but it causes the most problems when young cannabis seedlings are also stressed by too high levels of nutrients, or when started in a “hot” (nutrient-enriched) soil.

When underwatering is combined with too much nutrients, seedlings often become dark green and stunted, with twisted and discolored new growth.

The solution for this (underwatering + high levels of nutrients) is simply to give the plants more water so they can establish roots and start growing again. Most plants will be able to grow out of this problem once they get enough water to start growing. While it’s not always the best idea to start out with a hot soil mix, most seedlings will easily grow into it if given a good growing environment.

See also  How To Feminize Cannabis Seeds

This cannabis seedling is dark because it was underwatered in a “hot” soil mix, but after watering the plant as normal for a week or two, the plant started growing vigorously

3.) Nutrient Problems – leaves are yellow, discolored, crispy or have spots

Healthy cannabis leaves on seedlings should be green! Again, here’s what healthy leaves look like.. .

Healthy Leaves Look Like This

When the cannabis leaves of young plants stop being green, you need to react. Changes of color (such as yellowing, spots, burnt tips, etc) are usually a sign that there’s a problem when it comes to young cannabis plants.

The leaves of young cannabis plants & seedlings should be green!

Some common seedling nutrient problems include…

Too Much Nutrients

A nutrient toxicity is most common in dry or hot conditions, when starting in “hot” soil, and when plants are underwatered.

Two of the most common signs of nutrient toxicty are tip burn and dark leaves.

Tip burn is a sure sign that the plant took up too much nutrients

A closeup of nutrient tip burn

Nutrient burned tips eventually start curling upwards if nutrient levels are too high for too long

Very dark leaves often indicate a nitrogen toxicity (too much nitrogen)

If a nitrogen toxicity is left too long, it starts causing other nutrient problems, like the yellow lines on the bottom leaves of this plant.

Causes of Nutrient Toxicity

  • “Hot” Potting Mix – Sometimes seedlings get a nutrient toxicity when started ing a “hot” potting mix (one that has a lot of nutrients). If it’s good soil and you’re watering properly, your seedlings will be able to grow out of this relatively quickly.
  • Slow-Release Soil – Nutrient toxicities are common when grower start with a “extended release” soil like Miracle-Gro original soil – you don’t want any type of soil that will be slowly releasing nitrogen throughout the grow; it will cause nutrient burn and reduced bud development in the flowering stage. Avoid original Miracle-Gro soil and any other slow-release soils!
  • Give Nutrients Too Soon – Giving nutrients too early will overload the seedling with nutrients – in a good soil potting mix, additional nutrients usually aren’t needed for the first few weeks at least
  • Give Too Much Nutrients At Once – Giving too much nutrients at once can cause a toxicity overnight – always start at half the recommended dose according to the nutrient schedule (most cannabis nutrients come with a nutrient schedule), and see how your plants react before upping the dose

Too much nutrients too soon caused this (tip burn)

While the above seedling may look light colored, the problem is actually that it was given too high levels of nutrients.

When there’s too many nutrients, the plant can start getting light colored because some nutrients are getting locked out. The tip burn on the leaves is a good indicator that this problem is caused by too many nutrients. Also this grower started with a “hot” (nutrient rich) soil mix, and there’s no way a plant this size could have already used up all those nutrients.

A lot of growers may think the way to fix this is add more nutrients since the plant leaves are pale, but that will actually make things worse! This plant just needs some plain water until it starts to use up the nutrients in the soil, and it will soon take on a healthy green appearance on new leaves.

Not Enough or Wrong Kind of Nutrients

Nutrient deficiencies and other nutrient problems are most common when growers are using the wrong type of potting mix or cannabis nutrients.

Two of the most common signs of nutrient deficiencies are pale or yellowing leaves and other unusual leaf discoloration.

The most common type of deficiency is a nitrogen deficiency.

The yellow leaves of a nitrogen deficiency may show signs of brown, and they will usually become soft and sort of “fold” in, before turning crispy and falling off on their own.

If the yellowing leaves are at the top of your plant or the yellow leaves are mosty new growth, then you probably don’t have a nitrogen deficiency. Nitrogen deficiencies affect the oldest, lowest leaves first.

Nitrogen Deficiency Leaf Closeup

There are many other nutrient deficiencies, and you can view them all here…

Causes of Nutrient Deficiencies and Problems

  • Soilless Medium w/o Hydro Nutrients – Some growers may start in a soilless medium and not realize it has no nutrients (with a soilless medium like vermiculite, coco coir, pertlie, rockwool, etc, it’s up to the grower to provide all the nutrients since they are inert mediums and don’t contain any nutrients on their own) which results in a deficiency if grower isn’t providing extra nutrients. Soilless mediums are easy to grow in, but they do require the grower provide nutrients from the beginning.
  • Don’t Provide Nutrients As Plant Uses Up Soil – Many growers start in a good soil that has nutrients, but don’t give nutrients or transplant seedlings to a bigger container when the plant has started to use up the nutrients in the soil
  • Wrong Type of Nutrients – Nutrient deficiencies commonly show up with the grower gives their plants the the wrong type of nutrients – generally it’s a good idea to give a “vegetative” nutrient formula for the first part of the plant’s life and a “bloom” nutrient formula for the flowering/budding stage. When giving the wrong time of nutrients at the wrong time, your plant won’t grow as well. If you give vegetative nutrients in the flowering stage, you make it harder for the plant to form buds, while also increasing the chance of getting nutrient burn and other nutrient problems.

Other Nutrient Problems

  • Not Maintaining pH – If growers don’t manage pH, their plants may show signs of nutrient deficiencies even if the nutrients are actually there near the roots.
  • Improper Watering Technique – Growers who don’t water properly (growing mediums stays wet or dry for too long, poor drainage, etc) often start getting nutrient deficiencies as the plant isn’t able to effectively carry out normal plant processes
  • Too Small Container – Nutrient problems crop up when plants are kept in a small container for too long without being transferred to a bigger pot (this is known as being “root bound” and can cause the plant to display nutrient deficiencies because the roots aren’t functioning properly)
  • Bugs– a lot of bugs and pests may initially look like a deficiency (spots on the leaves can appear from bites, or if bugs have infested the soil, etc)

4.) Heat – leaves bend in the middle so they look like canoes or tacos, turning up at the edges, wilting, strange spotting, symptoms usually appear after temperature starts climbing.

When the heat gets too high, the edges of the leaves will begin to curl up and the leaves will begin to “cup” or “taco.”

Here’s another cannabis seedling suffering from heat stress – notice how the edges are curling upwards. The solution to this problem is simply to lower the heat as experienced by the plant.

Sometimes the leaves sort of fold downwards due to heat, too, like this seedling

After being subjected to overwatering plus a heat wave, the leaves of the following seedling started cuppping upwards and turned lime green. The stems and veins of the leaves were turning red. You can see the soil is still dark and wet because the plant stopped drinking after developing root problems.

Cannabis plants often display heat stress when grown in hot, dry weather, especially when not given the right amount of water.

Learn more about cannabis heat stress and how to fix it: https://www.growweedeasy.com/heat-light-stress

5.) Not enough (or too much) light – burned or crinkled leaves, too much space between nodes, tall seedlings that fall over

Not Enough Light = Stretched, “Leggy,” Tall Seedlings

Too Much Light = Burned, Crinkled Leaves

Stretched, “Leggy,” Tall Seedlings – Give More Light!

This seedling is stretching too tall, with a lot of space in between sets of leaves, and a long thin stalk. This is caused by the plant not getting enough light. It’s “reaching” upwards, trying to find the sun.

More seedlings stretching from lack of light

To fix too-tall seedlings, simply provide more light (usually by bringing grow lights closer or getting a brighter grow light)

After giving enough light, growers can bury the extra stem, or just wait until the seedling grows out of it on its own

Burned, Crinkled Leaves – Reduce Light or Move Grow Lights Up

This cannabis seedling basically grew up into the grow light!

This cannabis seedling is being burned by too-close LED grow lights

FAQs – Frequently Asked Questions

Question: What do seedlings like?

Answer: Moist but not drowning conditions, warmer temps, and a bit of light to help them start growing. Very little nutrients to start.

Question: How do I avoid germination problems?

Answer: Before anyone worries about cannabis seedling problems, it’s important to get your cannabis seeds to sprout!

So make sure you are avoiding these common germination mistakes!

Most importantly, just remember that cannabis seeds like a warm, moist environment to sprout.

Common Germination problems

  • Too wet – don’t drown your seeds! While it’s okay to soak seeds for the first 24 hours, after that they should be moist but not soaking.
  • Too dry – if seeds are too dry, they won’t sprout! If seeds sprout but then are exposed to dryness, they will die.
  • Too deep – if you plant seeds too deep in the growing medium, they may have a hard time making it to the surface. An inch deep (just enough to support the seed and cover it) is about as deep as you’ll ever need to go.
  • Not warm enough – seeds and seedlings like warmer temps (from 80-85 F) and will grow more slowly in cooler environments.
  • Wrong starting growing medium – Many growers like to plant their seeds directly in a growing medium, just like in nature. But some growing mediums are better for seeds than others. Learn more about the pros and cons of different starting growing mediums here.
  • Old or improperly stored seeds – any seeds that germinates is a good seeds, but older or improperly stored seeds often take longer to sprout, and may no sprout at all, even if you do everything right.
  • Not ripe seeds (pale or translucent) – while any seed that sprouts is a good seed, seeds that are pale, flimsy or translucent have very low germination rates because they’re not fully mature.
  • Too much humidity – Some growers like to use a humidity dome for new seedlings, but don’t leaves these on too long after sprouting, as too much humidity can cause “damping off (seedling sort of folding over and dying, more info below)

Question: Am I drowning my plants? I planted my seeds two days ago in moist soil, I watered them a little, but no waterlogging. I then stopped watering them for fear of drowning them. Today, the top of the soil is getting dry, there’s still some moisture left in it, but not much from what I can tell. Should I keep it moist or just leave it be?

Answer: Young seedlings can get easily drowned, especially in a big container (learn about different containers for growing cannabis). But at the same time, they like moist conditions, and seedling roots should NEVER dry out as this can kill or seriously stunt your plant.

But how to balance the need for both water and air?

In a smaller container like a solo cup, it’s very difficult to overwater young seedlings as long as there’s plenty of drainage and you’re using a good growing medium. Once seedlings have started to outgrow a small container, you can transfer to a bigger container and the seedling will be much more robust.

If you’ve started your seedling in a big container, it’s good to be worried about overwatering young seedlings. In a large container, it generally takes a relatively long time for the growing medium to dry out, and your seedlings aren’t drinking much. Therefore it’s easy for them to get waterlogged. In this situation, you can use a spray bottle or a mister to mist the area around the plant thoroughly, which will seep down to the roots and keep them wet, but won’t soak the soil. Another option is to use just a small amount of water, maybe a cup at a time, and water in a circle around your plant until it starts growing vigorously. Giving seedlings just a bit of water at a time prevents them from getting drowned in drenched soil.

Once the plant is growing fast, you can start watering as normal (water until 20% runoff comes out the bottom, then don’t water again until the top inch is dry to the touch). At this point your plant will be drinking more and will have a stronger root system to seek out both the water and the oxygen it needs.

After reading this article, all your seedlings will look as green and happy as this one!