Cannabis Seedling Stage Guide (Baby Weed Plants)

Cannabis Seedling Stage Guide (Baby Weed Plants)

The cannabis seedling stage is the time when your weed plants are at their most tender and vulnerable. It seems like a long journey before they will be harvest-ready plants, with either feminized seeds or autoflower seeds.

Learning how to protect and care for your seedlings is essential - and luckily, it isn't that difficult. In our guide to growing healthy cannabis seedlings, we explain everything you need to know to properly take care of your baby weed plants, which contains all you need to know.

The cannabis seedling stage starts with germination

When weed seeds burst into life and sprout two tiny leaves and send roots into the soil (or whatever germinating medium you are using), they are known as seedlings. Keep an eye on the seeds to check that the soil does not dry out, and after a few weeks, you should see signs that the cannabis seeds are splitting and the tendril emerging.

This tendril will head downwards into the soil and eventually form the taproot. The tiny white spike is the first sign of life of a new cannabis plant. Nothing is more rewarding than seeing the evidence that the seeds you have carefully selected have woken from their dormancy. Your cannabis seedlings are embarking on a new life stage which will end in rich rewards for you!

Meanwhile, the husk of the seeds splits into two and provides energy to fuel the growth of the seedlings. You should soon see two leaves unfurling. These first leaves are known as 'sucker leaves' or cotyledons and are smooth and round. Don't worry if they look nothing like cannabis leaves; this is normal for healthy seedlings.

All plants begin by producing sucker leaves. Their role is to support photosynthesis and collect enough energy for the plant to grow. The next pairs of leaves should be more cannabis-like in appearance, although it will take a while before the baby cannabis plant is mature enough to produce genuine cannabis leaves.

How to protect your baby weed plants?

Marijuana seedlings, as is the case for all young plants, are extremely vulnerable to many types of danger. Birds may eat them; they could be damaged by frost, dry out from lack of water, or ravaged by pests. Some may die from unknown causes, and this is common, but you need to do all you can to protect them until they grow into strong young cannabis plants.

They need a shelter with some sort of transparent, plastic shield. If you plan on growing cannabis seedlings outdoors, you could place them under plastic bottles, cut in half with extra slots cut into the sides to promote airflow. These protect vulnerable seedlings from excess rain as well as predators. You can buy ready-made cloches at garden centers.

When germinating cannabis seeds indoors, just make sure that they are in a safe place, well away from any children and pets. Nothing is more annoying than finding a cat sitting on a tray of sprouting seedlings!


One of the most common causes of death in seedlings is root rot, caused by overwatering and insufficient oxygen in the soil or substrate. This is more likely to happen with beginner growers who have no gardening experience.

Healthy cannabis seedlings have very few needs; they do not need too much water. If water swamps the delicate root system, they will quickly cease to grow and die in the space of a few days. One way of preventing this is to use small pots for seedlings, as the soil dries much more quickly than in larger containers.

Weed seedlings should be watered carefully. Do not pour a watering can of water all over them, for example, or use a hosepipe, unless you want to drown them or wash them away. Use small amounts of water and use a small jug or sprayer for watering cannabis seedlings; this helps with giving the right amount of water gradually.

Don't give so much water that it puddles, but equally, do not allow the soil or substrate to dry out.

If you have forgotten to water your cannabis plants for a few days, you may find that the soil has dried out so much that the water runs straight out the pot. If this happens - which it shouldn't as you need to check your seedlings a couple of times each day! - add water ten minutes later, and then twenty minutes later, and so on. This enables the soil to absorb the water gradually.

Which water is best for cannabis seedlings?

Across the world, there are two types of water; hard water and soft water. Hard water has high levels of calcium and magnesium. Calcium deposits can cause problems to cannabis roots as they can build up in the soil and prevent the absorption of other essential nutrients, thus leading to eventual nutrient deficiencies.

Soft water has no mineral deposits whatsoever. Rainwater is technically soft water, but by the time it filters to the plants' roots through the soil, it is usually filled with useful minerals.

Rainwater is the ideal water for cannabis seedlings, but if accessing rainwater is problematic, and you live in an area with hard water, you could try distilled, ionized or purified water.

Do cannabis seedlings need nutrients?

No, seedlings do not need extra nutrients. When they have used all the extra energy supplied by the sucker leaves and seed husk, they will require nutrients from an outside source, but not until they have acquired three to four sets of true leaves and are well on their way in the vegetative phase.

If you would give extra nutrients in this growing stage, you can risk nutrient burn, which can cause severely stunted growth.

The best time to give plants their first dose of fertilizer is when you transplant cannabis seedlings to larger containers - day one of the vegetative stage. If you want to learn more about how to properly transplant seedlings, you can consult our guide to transplanting cannabis plants.

Lighting requirements for weed seedlings

It is perfectly possible to use window light to grow cannabis seedlings, which is certainly the cheapest option. A sunny window sill is fine for the first few weeks after they have germinated.

After a couple of weeks, however, it would be best to get a proper LED grow light, so you can regulate the light cycles at 18/6 or 24hrs.

Seedlings can be grown under fluorescent lighting such as spiral compact fluorescents, tube fluorescents, LEDs, or Metal Halides, which supply a blue light, which cannabis plants use to point towards the light source (phototropism). Avoid incandescent lights, as these emit too much heat and insufficient light and can easily damage delicate seedlings.

LEDs are ideal as they emit hardly any heat. If you use a light source with a high wattage, make sure it is not placed too close to your plants.

Tips for caring for your baby weed plants

  • If you want to be a successful cannabis grower, it is important to establish a watering and lighting schedule from the outset and to get into the habit of regularly checking on your marijuana plants.

  • Use reflectors or grow tents to maximize the distribution of light.

  • A slight breeze will encourage your shoots to become strong and more likely to grow into a healthy cannabis seedling. This is because the shoots are forced to focus their energies on reinforcement, rather than simply growing upwards. Try and mimic natural conditions as much as possible, and seedlings in the wild would certainly be subject to gentle breezes.

  • Look out for indications of stalking fungi. Pythium and Rhizoctonia are extremely common parasitic fungi that cause young seedlings to develop a disease known as 'Damping off' that results in your weed plants withering and dying. You can reduce the risk of Damping off affecting your seedlings by always using good sanitation methods, ensuring that the soil is well-drained, and never reusing compost or any other growing medium.

What have we learned

Caring for your cannabis seedlings is essential for a successful harvest. To protect your baby weed plants, provide shelter with a transparent plastic shield or cloche. Water them carefully, avoiding overwatering that can lead to root rot.

Rainwater is ideal, and no extra nutrients are needed until they have three to four sets of true leaves. Start with window light, then transition to LED grow lights for optimal growth. Establish a watering and lighting schedule, use reflectors, and mimic natural conditions with gentle breezes. Watch for signs of fungal diseases, as this can be quite dangerous to any healthy plant.

The next phase of your growing process is the 'Cannabis Vegetative Stage', read up and make sure you are ready to care for your adult plants. If you want to learn more about the art of growing cannabis, you can check out our Learning Center for more guides like this.