Hello Nico! I am need of information on seedlings. Can you please give me some data on how warm it needs to be for seedlings? When can I introduce them to my hotter lamps? Any other tips for a beginner? Many thanks for all you do! — Angie R. via the mailbag at NicosNuggets@hightimes.com
Howdy, Angie. Thanks for reading HT.com and writing in with a question!
The infancy stage for cannabis plants, such as seedlings or new cuttings, is crucial for a plant’s development. Starting them off on the right foot helps ensure a healthy life for each plant as it grows and develops towards its flowering and harvest stages.
Whether you are propagating from seed or starting clones from cuttings, there are a few simple tricks to help ensure good rooting and robust growth. Good root structure and preventing young seedlings and clones from stretching are the keys to strong plant development. Root mass will directly correlate to the growth and overall size of your plants.
To start, keeping the root zone temperature around 80°F is essential for rooting plants. Warmer temps between 78° – 82°F will result in faster rooting. Heat mats are excellent sources of heat and can aid in keeping temperatures consistent during colder months.
Next, deploying a humidor tray and dome system will also go a long way in helping plants develop strong root systems. Humidity ranging between 68 – 72 percent is perfect for seedlings and clones trying to root.
Additionally, a small amount of rooting hormone at the base of the cutting or inside your seed plugs can also help a great deal. There should be no need to use nutrients in your medium at this stage. Once root tips start to protrude from the plugs or medium, the seedlings will be ready to transplant into a larger container and grow medium. At that point, a very mild nutrient solution may be applied. Be sure to measure the pH of your runoff, keeping pH levels between 5.2 – 5.8 for rooting cells for maximum nutrient uptake and less risk of root burn.
Light cycles are also extremely important for seedlings and clones. Cool running light sources, such as fluorescent lamps, are ideal because you can keep them closer to the plants without risk of overheating. Keeping lamps closer to the young plants will help prevent them from stretching and will promote more robust growth. Fluorescent lamps also are heavier in the blue spectrum, which keep internode lengths shorter and prevent plants from stretching.
Next, it is very important to remember that roots breath in oxygen, not CO2, and they do so at nighttime. The dark cycle is critical for rooting plants because this is the time when leaves and stems also transfer energy down to the root zone. Roots grow mostly during the dark cycle, so having 6 – 8 hours of dark in every 24-hour period is strongly recommended. Once your plants are rooted and transplanted into larger containers and stronger grow medium, you can move them under your HID lighting.
Remember, though, they are still babies and will need to have the lights a bit higher and the temperature a bit lower than usual as young plants can go into shock after transplanting if not done properly. Keep your light cycle at 18-on and 6-off, and keep the temps around 74° – 76°F for another week, before getting it down to 72°F and 40 percent humidity.
Thanks for reading everyone and remember: Grow… And help the world grow, too!
Got questions? Email ‘em over to Nico at NicosNuggets@hightimes.com and be sure to put “Nico’s Nuggets” in the subject line! (Tip: Before sending a question, try the new Search feature on the HIGH TIMES website. Simply click the “magnifier” icon at the top right and type “Nico + your subject topic” to see if your question has already been answered!)