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

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

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Read our article for week 1

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

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

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

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

Week 2

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

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How Big Should My Weed Plants be After 2 Weeks?

In most cases your plant should be around 2 to 3 inches tall with 2 to 3 sets of leaves including the cotyledons (seed leaves which are rounded). Results may vary but it would greatly depend on the quality of your seeds, the soil you’re germinating in and the quality of the light they’re receiving.

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

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Do I need to start giving my plants fertilizer now?

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

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

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

Uh Oh, Your Cannabis Seeds Didn’t Sprout

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

Too wet, or too dry

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

Too cold, or too hot

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

Planting too deep, or too shallow

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

Bad seeds or genetics

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

Cannabis sprout 13 days after planting

This is the same sprout 13 days from germination.

Week 3

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

Keep your soil moist (not wet) and avoid overwatering or letting your plant dry out.

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

Feeding Cannabis Sprouts

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

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


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

Give them light

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

Thanks for taking the time to read this article. If you found it in any way helpful, please share it with others who might benefit.

If you have any questions, please fill in a comment below. I will try and answer them as fast as possible.

Mike Drouin

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