Most Common Cannabis Seedling Problems

The most vulnerable time in any plant’s life is its seedling phase. This means you will need to be well acquainted with the potential problems that could occur so as to ensure a healthy beginning and future of your plant’s life. If your plant has made it through its seedling phase, the chances of survival are much higher.

In general, each issue that your seedling can encounter comes with its own sets of symptoms and treatments. The most likely seedling problems you might run into are:

  • Overwatered seedling
  • Underwatered seedling
  • Nutrient imbalances
  • Temperature issues
  • Lighting issues


-seedling is droopy
-growing medium is moist
-damping off

Although we refer to it as “overwatering,” the problem itself comes from a lack of oxygen rather than an overabundance of water. Hydroponics systems, where plants are literally “planted” in water, work perfectly fine as long as there is enough dissolved oxygen in the water. 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. You can prevent overwatering by keeping container plants growing in a pot that is relative in size to the plant. Large pots lead to a higher chance of overwatering. Also, make sure that the drainage holes are in working form, are numerous enough, and that the soil is airy enough rather than having too much packed clay. 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. Start seedlings in smaller container until they’re growing vigorously, then transfer to a larger container. Sometimes overwatering has more to do with frequency than quantity. Make sure that you are allowing plenty of drying time in between waterings, otherwise the soil will not receive enough oxygen.

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.


-seedling is droopy
-wilting, or not growing properly
-the growing medium around the seedling isn’t moist

Although it happens less often than overwatering, it is still a serious problem that could negatively impact your seedling. It happens especially with beginners who have been warned – ‘never overwater your plants,’ so they overcompensate in the opposite direction. Plants are always losing moisture via their leaves through transpiration, which means they need a constant supply of water to continue functioning properly. It’s important to remember that this moisture needs to be at the root level since that’s where water is absorbed and transported throughout the rest of the plant. Plants of any age will die if the roots dry out, but in seedlings this can happen much more quickly. If you look at the soil and you see that it has begun to separate from the container, this means that it is far too dry to be healthy for your plant. Underwatering is an especially grievous offense when it is combined with an overdose of nutrients. The solution for this 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.

Nutrient imbalances

-leaves are yellow, discolored, crispy or have spots

Your seedlings could either experience a nutrient toxicity or deficiency, both of which will have adverse effects. Yellow, crispy, spotted, discolored leaves are a sure sign of some sort of nutrient deficiency. Seedlings should never be any color besides green; if they are, you know there’s a problem with them. Sometimes nutrient imbalances come about because of the pH level being off, or the wrong nutrients being fed to your plants or just the wrong proportions of 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. When there’s too many nutrients, the plant also can start getting light colored because some nutrients are getting locked out. 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. Acctually the 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.

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Nutrient deficiencies and other nutrient problems are most common when growers are using the wrong type of potting mix or cannabis nutrients. If your plant has a nutrient deficiency, then its leaves will probably look pale or yellowing, and you might also see signs of other leaf discoloration. A nitrogen deficiency is almost always at fault, and this will make the leaves include brown with the yellow, and will go soft and will fold before they become crispy and drop off the plant. A nitrogen deficiency generally affects the oldest leaves at the bottom of the plant before it reaches the other leaves elsewhere. You need to use the right mix during the correct stage of life. Use a vegetative formula for your plant’s beginning part of life, and a “bloom” formula for the flowering and budding stage.

Another common nutrient problem with marijuana plants is a pH imbalance. Make sure to always maintain a balanced pH level, and you should be aware of the fact that the pH level will fluctuate. Improper watering will also cause a nutrient deficiency if left too long.

Temperature issues

When the heat gets too high, the edges of the leaves will begin to curl up and the leaves will begin to “cup”. Cannabis plants often display heat stress when grown in hot, dry weather, especially when not given the right amount of water. Be sure to always know what the temperature of your grow room is. Seedlings are happiest when the temperature is somewhere between 68 degrees and 77 degrees Fahrenheit. An additional way to keep the temperatures lower is to keep the lights far enough away from your seedlings so as not to burn them.

Lighting issues

-Not Enough Light = Stretched, “Leggy,” Tall Seedlings
-Too Much Light = Burned, Crinkled Leaves

Whether it’s too much or too little, improper lighting can cause some serious problems for your marijuana seedlings. Luckily, it’s usually an easy fix: just move the lamps closer to or further away from your plants. If you are growing your plants outdoors, try covering them up on extremely hot days, and make sure every bit of your plant is exposed to direct sunlight.

In general, your seedlings are going to want a moist environment, warm temperatures, and some light. They aren’t going to want much for nutrients. As long as you follow these points, your seedlings should be perfectly happy and healthy. Remember that plants with strong genetics have less chance of getting sick and are less vulnerable for diseases, deficiency’s, pest and environmental stresses. So make sure to buy cannabis seeds from a trusted seed bank.

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