All About the Cannabis Seedling Stage

Cannabis grows in stages: germination, seedling, vegetative, and flowering. The first phase is germination, which happens in the first 3 to 10 days. Next comes the cannabis seedling stage and lasts about 2-3 weeks after the germination phase. 

Following is the vegetative stage that lasts from week 3 to 16 weeks. The final one is the flowering cannabis phase at weeks 8 to 12. The vegetative and flowering stage tend to happen simultaneously, as new growth and more mature leaves live on the same crop. 

One of the most critical phases is the cannabis seedling stage because the weed plant is vulnerable and growing rapidly. Is your harvest currently in this phase, and you need to know more? Read on to find out everything you need to know about the seedling phase of marijuana. 

What happens with a young plant during this stage?

Your cannabis plant enters the seedling stage when the seeds begin to sprout. The shell will split, and a tiny white tendril will start to poke out. Soon a tiny stalk will emerge from the growing material, and more roots will grow downward. 

In rare cases, a seed shell can be stuck to a seedling so that a young plant can’t receive the needed light. For this reason, it is essential that you help a plant and remove the seed shell delicately and gently as a part of your cannabis seedling care.

In the latter days of the seedling stage, the initial two leaves will form at the top of the stem. The weed plant will continue to develop upward with more leaves, and the roots will become stronger until it enters the vegetative stage. 

How to care about cannabis seedlings properly

During the cannabis seedling phase, the crop is very weak and prone to diseases. If not taken care of properly, the entire marijuana plant might die or not continue growing. This is one of the most interactive stages in the crop’s life.   

The right container

When you’re looking at what container you should plant your marijuana seedling in, there are a few things to consider.

For autoflower seeds, you should put them in the final container that they’ll grow into the vegetative and flowering stage. Autoflower strains have a short life cycle, so you don’t want to put them through any unwanted stress from transplanting. For more details, check our “autoflower pot size” report.

If you have a seedling from a feminized seed, start them in germination pots to ensure they’re healthy in the initial part of life. The marijuana plant can stay there through the seedling stage (2-3 weeks). Transport the crop once leaves start to form that are bigger than the container. 

For all types of containers, you want to make sure that there are drainage holes, aeration, and the proper size for the types of marijuana strain. Seedlings do well in propagators.

Drainage is essential because still water will encourage mold, fungi, or other pathogens. This can be deadly for small seedlings with no immunity to diseases. Aerationis vital because roots need to breathe too. It results in healthier and faster growth. 

To determine the correct pot size, you need to do some homework. Read up about the cannabis strain, how big it should grow, and for how long. Too big of a container, there’s a risk of overwatering and malnutrition. Too small, the roots can’t grow enough, which can result in stunted growth. 

The medium 

At the beginning of cannabis life, you want your cannabis seedlings to use a light and slightly acidic medium. The pH needs to be between 6.3 to 6.5. The growing medium has to be well-aerated as well. 

You can add 20 to 50% of perlite to the medium to help with nutrient (nute) retention and aeration. Marijuana at the seedling stage is sensitive to nutrients. You don’t want to shock your plant with a lot of nutes in the beginning of the life.  

You can use any potting material for growing cannabis seedlings, and it’s just important to keep an eye on these factors. 

A word about genetics

Growing marijuana takes a lot of work and knowledge. Understanding the genetics of your weed seed will help you provide quality cannabis seedling care. 

Some cannabis seedlings need more light, nutes, or space to grow than others. Other cannabis strains grow taller, and some grow wider. Certain marijuana types grow better indoors than outdoors, or vice versa. 

Do your homework before planting your weed seeds to ensure you’re doing everything correctly. If you’re a beginner, look for low-maintenance, stable strains, so you can learn how to grow marijuana without other factors. 

What else to consider when caring about cannabis seedlings?

Now you have the correct container, growing medium, and know about your seedling’s genetics, it’s time to look at care. All marijuana growers want successful seedlings because this is the first stage of life and what sets the stage for the rest of their existence. 

Watering and pot size

Watering weed during the seedling stage is very important. You need to find an adequate amount of H2O based on the pot size and drainage. Use big containers (bigger than 2 gallons) to water seedlings, especially autoflowers. Do not overwater them, give them “a sip” of water every time till your seedlings “grows into” their pots.

Symptoms of an overwatering include dropping seedlings, a very moist growing medium, and damping off. The reason for this could be that the container is too big for the seedling. Another could be that the pot size is correct, but the drainage is bad, or you’re watering too often. Overwatering is often a root of the most cannabis seedling problems.

Signs of underwatering are wilting seedlings, a dry growing medium, and slow growth. The leaves might look crispy or be fading in color. To correct this, you need to up your watering schedule. 

You can tell a healthy amount of moisture when the growing material still looks damp after watering. You determine the pot size based on the strain of marijuana. Most growers will use a sprayer to water their weed crops during seedling to prevent overwatering. 

Lighting

Cannabis seedlings need plenty of light to grow. They produce energy through photosynthesis, which requires sufficient rays to work.

In some areas, natural sunlight will be enough to grow healthy cannabis seedlings. However, if you live in the northern USA, purchasing artificial growing lights is essential. The weed season is shorter in those parts of the country because of the light and temperature. 

Regardless of where you live, if you have an indoor garden, extra lighting is almost always needed because windows don’t  let in sunlight all day. A cannabis seedling light schedule is 18 hours of sun each day with 6 hours of darkness. 

Temperature

The temperature for the seedling stage is essential for the proper growth of plants. When the degree is too high or low, the roots can’t absorb nutes, which leads to a deficiency, stunted growth, and death. 

A hot 73 degrees Fahrenheit is the correct cannabis seedling temperature. It’s vital to remember that many things put off heat, such as humidifiers, lights, or other electronics in the room. Take this into consideration when setting the temperature in the room. 

If the garden is getting cold a lot, look at the ventilation system, cracks in the windows, or any other areas that could let cool air in. 

Nutrients

You might be thinking that you need to load up on cannabis nutrients during the seedlings stage, but that’s not the case. 

Weed at the seedling phase doesn’t need any nutrients up to the first week after germination since the cotyledons inside a seed provide the sprout with all the initial micro elements to sustain growth. In 1 week after germination, the seedling requires just a small amount of fertilizers (mainly N, P, and K).

Giving a cannabis seedling too many nutes will result in toxicity. If this happens, watering will help dilute the growing medium. It’s better to look for fertilizers that are slow-release to avoid this from happening. 

On the other hand, fragile young marijuana can experience a deficiency if you’re not giving them enough. A nute deficiency will result in the yellowing and folding of leaves. You’ll be able to tell more on the bottom leaves. 

Buy a balanced fertilizer to ensure the cannabis seedling nutrients are provided but not overdosed. 

Common causes of stunted growth in cannabis seedlings

If you see signs of stunted cannabis seedling growth, there are some direct causes. 

• Seedlings not getting sufficient light during the day. 
• The temperature of the garden is too hot or cold.
• The humidity level isn’t correct. It should be 40 to 60%.
• Water or growing material suffocates the roots.
• There’s a nutrient deficiency.
• A pathogen, pest, or other unwanted factor is attacking the plant. 
• Genetically, this marijuana strain is small.

Look at these areas and adjust if you find a problem. 

How to prevent nutrient problems

During the cannabis seedling stage, it’s essential not to overfeed or water. Use proper marijuana nutrients, but don’t give the full strength until the crop is mature. Instead, dilute the fertilizer to about 10 to 15%. 

This will ensure that the seedlings are getting nutes to grow but not in toxic amounts. If you accidentally give too many nutrients, flush the cannabis plant. Make sure there’s excellent drainage to avoid water buildup. 

How to avoid stretchy seedlings, pests, and bugs

Stretched out cannabis seedlings won’t produce sturdy stems needed to support leaves and buds. This happens where there isn’t enough light, and the marijuana plant is trying to get closer to what there is. If the temperature is too hot, this can happen. 

To avoid stretching out and other related seedling problems, make sure your garden has sufficient light on all parts of the plant, not just above. Next, monitor the heat to be about 78 degrees at all times. 

If your seedling is already stretched, bend it back and forth. This puts some stress on the stem, and it’ll rebuild stronger. When leaves start to grow, they’ll be able to handle the weight. 

Pests and bugs love warm and humid areas, which is the same environment marijuana thrives in. To avoid this, make sure there’s no standing water and the ventilation system has a screen. Bugs won’t be able to enter the garden if it’s secure. 

If they’ve already made their way in, use a trap or organic food grade pest control chemicals to kill them. Look for holes or areas that are letting them get in and patch them up. 

When and how to transplant cannabis seedlings

If you’re growing cannabis seeds in a different container than what you’ll use when it’s mature, you need to transplant cannabis seedlings. 

First, have all of the materials you need to transplant ready to go. These include water, pots, growing material, a butter knife, and a marker. 

Before starting, water the seedlings, as wet soil is easier to work with, resulting in less damage to the roots. Gently, slide the buttle knife around the seedling’s container to loosen it. Never tug hard. The roots and soil should slide out without a lot of pulling. 

Have the new pot nearby to plant and transfer. Tap the soil a little, so the seedling is now secure in the new growing medium. Label the container, so you know which cannabis strain it is. Water with light nutes and let them settle in. 

The end of the seedling stage

The marijuana plant is out of the cannabis seedling stage when it starts to form real leaves. This happens after about 3 weeks of growing. 

You then enter the cannabis vegetative stage, and need to follow a whole new procedure. Now you know everything about growing happy and healthy seedlings, it’s time to buy cannabis seeds and get planting today! 

About the author: Kyle Kushman

13 times Cannabis Cups winner. Kyle Kushman is a master breeder and indoor growing expert, a leading voice in the fight for legalisation and education, especially when it comes to growing cannabis at home. He’s been teaching and spreading the word for over 30 years, maintaining a consistently high level of achievement throughout his entire career.