Sandwiched in-between germination and vegetation, the seedling stage can be one of the most challenging phases for new weed growers to get right. Since seedlings are so young and delicate, they’re far more susceptible to minor errors. Even experienced cannabis cultivators claim the seedling phase is the most prone to severe issues.
Although cannabis cultivators should always practice vigilance, growers must constantly monitor their seedlings. The more care and attention people put into the seedling stage, the more likely their plants will form robust roots.
Mastering Marijuana Seedlings — Tips For Growing Healthy Cannabis Seedlings
Don’t Nuke Your Seedlings With Nutes! — The Significance Of Proper Soil
It doesn’t matter how healthy your seedlings appear, they won’t survive if you place them in the wrong medium. Unless you’re an experienced cannabis cultivator, please never use nutrient-dense “living soils.” Instead, focus on well-aerated potting soils that have moderate nutrient levels.
Seedlings can quickly get “burned out” with excessively high concentrations of nutrients. Also, it’s more common for pathogens like mold to form in stagnant soil. For these reasons, cultivators must focus on soil blends with perlite to maintain healthy oxygen levels and avoid breeding fungi.
Many cannabis cultivators recommend putting a significant amount of perlite in potting soil for seedlings. Perlite is a fantastic soil amendment for aeration, so it will improve drainage and oxygen absorption. Aim for around 20 percent perlite in your potting soil during the seedling stage.
Also, please don’t forget to keep your soil pH within the desired “slightly acidic” range. Ideally, your soil should have a pH range of 5.8 – 6.2.
You can learn more in-depth details on the best cannabis soil in International High Life’s previous post, “Perfect Potting Soil For Pot.”
What Container Is The Right Fit For Seedlings?
Related to choosing suitable soil, cultivators need to consider the ideal container size for their seedlings. While there are professional starter kits on today’s market, many cannabis cultivators use standard red Solo cups throughout the seedling phase. These tend to give seedlings enough room to grow without increasing the risk of mold.
Seedlings need a happy medium of space to avoid getting root bound and get all the water they need. Containers that are too small increase the risk of the roots drying out and getting “bound” to the soil. However, if seedlings have too much space, they won’t enjoy easy & balanced access to water and oxygen. There’s also a greater risk that larger pots could retain excess water and increase the likelihood of mold.
Cannabis growers only recommend placing autoflower seedlings in a medium or large final container (about 5 – 10 L). Since autos grow faster than photoperiod strains, they won’t have as much time to recover after transplantation. This previous article can teach you all about growing autoflowering weed.
There may be variations in the ideal container size for your chosen strain, but it’s usually best to place photoperiod plants in containers the size of a red Solo cup. Just remember to cut a few holes in the bottom of these cups to improve drainage.
What’s The Standard Seedling Temperature & Humidity?
You must keep temperature and humidity levels relatively high during the seedling phase. Please remember that this stage should mimic the atmosphere in early spring in a subtropical zone.
While each strain may have slightly different preferences, most cultivators claim temperatures in the 70s Fahrenheit work well during the seedling stage. Bring this temp down to the lower end of the range if you notice signs of heat exhaustion like burnt leaves. Also, don’t be afraid to bring your temp down to the high 60s F during the nighttime.
As for humidity, most cultivators say they have the best success in the 50 – 60 percent range. Why does humidity have to be so high? Well, remember that seedlings are still developing their roots. In the early stages, seedlings rely on atmospheric moisture for their water requirements. It’s only as the cannabis plant matures that humidity becomes less significant.
You can gradually decrease the total humidity content as your seedlings get closer to the vegetative stage. However, you should keep relative humidity around 40 when your plants reach this point.
How Much Light Should You Shine On Seedlings?
Although seedlings need plenty of light to thrive, they can’t handle the full power of an LED panel or an HID bulb. Compact fluorescent lamps (CFLs) offer the best light intensity for seedlings with minimal risk of burn. Indeed, CFLs are so gentle that they can be placed as close as 6 inches from your seedlings without significant issues.
Although it’s best to rely on CFLs during the seedling phase, it’s possible to use an LED panel with a dimmer setting. However, using this method, you must hang your LED at least 18 inches above your plant and set it to dimmer. Even with the dimmer control, LEDs can be too powerful for some seedlings. Please monitor your plant’s emerging leaves for signs of burn and stress.
It’s also crucial to watch out for seedlings stretching too far to reach your light source. It’s common for seedlings to overextend early in their lives, resulting in weaker stems later on. To avoid this phenomenon, some cultivators recommend a 24-hour light schedule for the first few days and switching to 18 hours on and 6 hours off. Since the initial 24 hours of light are constant, your plants won’t feel deprived of light during these critical stages.
Watch Your Watering With Weed Seedlings
Overwatering is a common issue new cultivators often face during all stages of cannabis development. However, this avoidable mistake is extra deadly during the seedling phase. If you have a heavy hand with your watering schedule, there’s a good chance you’ll rob your seedlings of oxygen or increase the likelihood of mold.
The best way to avoid overwatering seedlings is to put your purified & pH-corrected water in a spray bottle. Gently mist your seedlings whenever you feel the soil is getting too dry. Typically, you won’t need more than ten sprays to give your seedlings enough moisture during each watering session.
If you’re unsure when’s the right time to water your seedlings, you may want to consider investing in a soil moisture meter. These devices can give you a more accurate read on how dry your soil is versus the standard “finger test.”
When Do You Know Seedlings Have Transitioned To Vegetation?
On average, seedlings take one to three weeks to reach the vegetative stage. However, you’ll need to inspect your seedlings’ leaves to know when they can handle the transition to vegetation.
Generally, cultivators recommend a seedling have at least three sets of serrated leaves before moving them to a larger container. The initial round leaves (aka cotyledons) should have fallen off or turned yellowish-brown before transitioning to vegetation.
Seedlings should also have a sturdy root structure before transplantation. You shouldn’t have difficulty lifting the soil plus roots out of your smaller containers. If you notice your plant’s roots appear in your cup’s drainage holes, you should transplant ASAP to avoid it getting root bound.
Please Seek Out Strain Specific Info On Your Seedlings!
Although most cannabis seedlings follow a similar growth pattern, please remember that each cannabis strain has unique preferences. The tips listed above should help you have a successful seedling phase, but checking what others say about growing your cannabis strain is always worthwhile.
Please take advantage of the numerous cannabis growing forums online to see if there are any special considerations for growing your preferred cannabis strain. Also, check out International High Life’s guide to “Growing Monster Cannabis Plants” for tips on picking the perfect pot strain.
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