The first four weeks of your cannabis plant’s life are arguably the most important. This early phase sets the foundation for the entire growth cycle—whether you're growing indoors or outdoors, from seed or clone.
During this stage, your plant’s root system is forming, leaf development begins, and its ability to absorb nutrients and light is established. That means understanding proper environmental conditions, watering practices, nutrient management, and lighting requirements is essential to success.
In this article, we’ll walk you through how to care for young cannabis plants—from germination to the end of week four—so you can set your grow up for healthy development and big yields.
Week 1: Germination and Seedling Emergence
To begin, you’ll need to plant or germinate your cannabis seeds. Planting the seed directly into the medium is the easiest way, but many growers prefer to germinate their seeds prior to planting. The paper towel method is one of the most popular and effective germination techniques: simply place seeds between moist paper towels in a warm, dark place (around 70-80°F / 21-26°C). After a day or two, you should see the taproot emerge.
Further Reading:The Ultimate Guide To Germinating Cannabis Seeds
Once the taproot appears, carefully plant the seed about a half inch deep in a light, airy seed-starting mix. Avoid nutrient-rich soil at this stage, as too many nutrients can burn delicate seedlings.
Use low-wattage LED or CFL lights on an 18/6 light cycle, and position them far enough away to avoid burning. Seedlings are fragile, and too much light intensity can be harmful.
Maintain a temperature range between 68-78°F / 20-25°C, with humidity between 65% and 70%. Gentle airflow is recommended, and many growers preform a light misting with water each day to help support early growth – but that is optional.
Week 2: First True Leaves Appear
By the second week, your seedlings should have shed their seed shells and developed their first sets of true leaves—the signature multi-bladed leaves associated with cannabis.
Continue the 18/6 light schedule and gradually move the lights closer to the plants to prevent stretching, which can cause weak stems. Be sure not to let the canopy temperature rise above 80°F/27°C. Some genetics can tolerate higher temperatures, but it’s generally recommended to play it safe during the seedling stage.
For autoflowering cannabis strains, many growers plant directly in the final container, eliminating the need for transplanting. Photoperiod strains, on the other hand, are often started in smaller containers and later transplanted into larger ones. At this point in week 2, the seedlings can remain in their smaller containers a bit longer.
Water the entire soil surface—not just directly around the stem—to encourage outward root growth. If your soil is already nutrient-rich, avoid feeding for now to prevent nutrient burn.
Week 3: Promoting Root and Leaf Growth
By week three, you’ll likely notice a growth surge in both the plant’s height and width. The root zone is expanding, and fan leaves with three to five blades should be forming.
You can move LED lights slightly closer, but keep them at least 20 inches above the canopy – if running at full power. If you’re using CFLs, they can be placed a lot closer due to their lower intensity.
Keep the relative humidity the same as last week, between 65% and 70%, and maintain a temperature range between 68-78°F / 20-25°C. Increase airflow with an oscillating fan to help strengthen stems and reduce moisture buildup.
This is a good time to introduce light vegetative nutrients at about ¼ to ½ strength. Make sure your nutrient mix includes nitrogen (N), phosphorus (P), and potassium (K), and consider adding calcium and magnesium if your base nutrients lack them.
Further Reading:The Science Of Cannabis Root Health
Week 4: Transition to Vegetative Growth
By the fourth week, your cannabis plant should be entering vegetative growth. It should have four to six sets of healthy leaves, a sturdy stem, and a well-developed root system.
Maintain the 18/6 light schedule, but now you can upgrade to higher-intensity lights like MH lamps or full-spectrum LEDs if you're growing indoors. Increase airflow to support stronger stems and improved nutrient uptake.
As the plant matures, begin increasing nutrient levels, according to your nutrient line’s feeding chart. This is also the ideal time to start low stress training (LST) or topping, if those techniques are part of your grow plan.
Further Reading: Introduction To Cannabis Plant Training Techniques
Caring For Young Cannabis Plants: Final Thoughts
The key to success during the early stages of growth is patience and consistency. With gentle lighting, proper humidity, and good watering habits, caring for cannabis seedlings doesn’t have to be complicated. Lay a strong foundation now, and you’ll set your plants up for healthy growth and high yields down the line.
Frequently Asked Questions
Question: What Should a 2-Week-Old Cannabis Plant Look Like?
Answer: A two-week-old cannabis seedling should be compact, with two or three sets of true leaves, a healthy green color, and no signs of stretching or yellowing.
Question: Do Cannabis Seedlings Need Darkness?
Answer: No—cannabis seedlings can be grown in 24-hours of light per day. However, they generally do best with 18 hours of light and 6 hours of darkness per day. Gentle, consistent light is key to promoting healthy early growth.
Question: How Do You Take Care of Cannabis Seedlings?
Answer: Use light, well-draining soil; keep humidity relatively high (65%–70% in early stages); water sparingly; and use gentle light to avoid stressing the young plants. Avoid fertilizing until true leaves appear.
Question: When Should I Start Feeding My Cannabis Seedlings?
Answer: This depends on whether your growing medium contains any nutrients to begin with. If you're using nutrient-rich soil, start feeding around day 20 to 30. If you're growing in coco coir or another inert medium, you can begin feeding the plant right away. Start with a light nutrient solution and gradually increase the strength as the plant matures.
Question: How Often Should I Water Seedlings?
Answer: Water only when the top inch of soil feels dry to the touch. Overwatering can lead to stunted growth and root rot, so air on the side of caution and avoid saturated soil.
Further Reading:3 Steps To Master The Seedling Stage
