If possible, you may want to consider growing your seedlings outdoors under direct sunlight. There is simply no substitute for Mother Nature, and seedlings in direct sunlight will grow healthy, strong stems with short internodes. Once your plants have developed 2–3 mature leaves, feel free to move them indoors, making sure to keep their lights at the right height to prevent any further stretching.
While cannabis seedlings like warm, humid conditions, too much heat can cause a plant’s leaves to grow slower than its stem, resulting in tall and stretchy growth. To promote healthy seedling growth, we recommend keeping the temperatures in your grow room or dome at 19–20°C during the day and roughly 13°C at night.
Thinning is a common agricultural technique that’s often forgotten among cannabis growers. As the name suggests, thinning is all about reducing competition among your plants by “thinning” out the population.
Another cause of leggy seedlings is heat.
To grow healthy seedlings, it’s important to give them the right amount and type of light as soon as they break out of their shells. Cannabis seedlings like to receive around 16 hours of light per day at an intensity of 375 lumens and 4000 lux.
Abnormal stretching in the seedling phase is a sign of stress. By far, the most common situation that causes seedlings to stretch and topple over is light deprivation.
Growing your seedlings under lights with a high percentage of red light may cause them to stretch. Blue light, on the other hand, helps to keep internodal spacing to a minimum and encourages plants to grow nice and stocky from the get-go.
Stretchy cannabis seedlings can be a pain to handle and transplant. Their stems can be very fragile, and once they start vegging, their foliage can be off-centre due to the weird stretch they underwent as seedlings.
Tip: Fungus gnats, which are tiny, dark, mosquito-like gnats, often appear when moisture and humidity levels are too high. Do not worry so much about getting rid of the gnats, but see them as a sign that something is off with the moisture content in your growing environment. The gnats will disappear on their own when moisture levels in the soil return to normal.
Unfortunately, damping-off can happen very quickly. Many times, a seedling can go from looking healthy to dropping dead in just one single day. When this happens, it is already too late to do anything since the fungus has already infected your plant and there is no method of recovery. However, you can learn to spot the signs of damping-off in order to prevent it from happening again.
When one seedling has already died from damping-off, chances are that your other seedlings are affected too, even if they’re still standing upright. One emergency measure you can try to stop the fungus from spreading is applying hydrogen peroxide. Sprinkle about 1ml (20 drops) of 3% strength peroxide onto the soil of each of your seedlings. The peroxide will kill the fungus. Obviously, there is no guarantee this will save your seedlings, especially if the disease has already progressed quite far. What’s most important is that you know how to prevent this occurrence from happening in the future.
HOW TO PREVENT DAMPING-OFF:
Damping-off is a common disease that can affect sprouting seeds, seedlings, or cuttings. It can be caused by several types of fungi, namely Pythium, Botrytis, and Fusarium. Pythium is most common. Although fungus is the main reason for damping-off, the disease is normally the result of several conditional factors.
The second factor can be that the substrate has been wet for too long, most likely from overwatering or due to poor drainage qualities.
Sometimes, the fungus can already be present in the growing medium or substrate that you use for germinating. This can happen when your substrate is not sterile.
Among the signs of damping-off include small white spots at the lowest part of the stem, just above the soil line. In this same area, the stem will look weak and thin, featuring a darker colour. If you spot these signs and the seedling is still upright, it is only a matter of hours until it will tip over.
If you don’t have the heart to thin them, pot them up instead. You can repot seedlings once they are twice as tall as the original container.
Finding mold on seedlings is frustrating! In this post, I’ll show you step-by-step how to get rid of mold growing on your germinating seeds, starts, soil, and pots, and prevent it from coming back.
Ideally, try to keep soil evenly moist, allowing the top part to dry out slightly between waterings. Never let it dry out completely though.
The main causes are overwatering, improper ventilation, too much heat, and/or overcrowding. All of which I’ll talk about in detail below.
Sorry, but I can’t say for sure. I would certainly recommend getting rid of the mold in your seed trays, because I can say for certain that it’s not good for your seedlings. 🙂