For all plants, including cannabis seedlings, the early stage is a dangerous and volatile time. Small environmental changes or inconsistencies can mean disaster because these tiny plants are so sensitive to climatic shifts.
Too much light, water, or nutrients can push little seedlings over the edge. They are also extremely susceptible to pests and disease. What conditions can you encourage for healthy seedlings? What should you avoid?
Let’s answer all your questions about cannabis seedlings, including what to feed them and when.
What should I feed my seedlings?
In the beginning, you shouldn’t feed your cannabis seedlings any nutrients.
Why? Because technically, in the first few weeks, the seed provides the sprout with everything it needs to survive (except water).
So long as you water your seedling tray regularly, it shouldn’t need any extra food until it’s three weeks old — or when it’s just entering the vegetative stage.
When should I feed cannabis seedlings?
Another trick question — because you probably shouldn’t feed your seedlings until they hit the vegetative stage, which means once it has developed three or more true leaves.
Until then, the tiny seedling will be pulling all the nutrients it needs from its seed husk and the available water. In this regard, the seedling stage is simple.
Why are my cannabis seedlings falling over?
If your little sprouts have started to fall over, chances are they have stretched. Stretching is when sprouts grow too tall too fast, and the plant structure cannot support the weight and height. Stretching is a stress response.
The most likely scenario is that you aren’t providing enough direct light, which encourages your plants to stretch out to find more. Light deprivation may also happen if you’ve placed the lights too far away, they aren’t intense enough, or the schedule is wrong.
Give seedlings 16 hours of light per day via a fixture placed just three inches above the canopy surface.
What kind of light? Some resources suggest a 12W CFL bulb for every couple of seedlings, or even a T8 four-bulb fluorescent will work. Seedlings are sensitive, so nothing too intense.
If you invest in a true LED grow light designed for later stages of growth, ensure you install it much farther away from the top of the seedling to avoid burning it.
Why are my seedlings growing so slowly?
If your seedlings are growing too slowly for you, one of the necessities of life isn’t optimal. You’ll have to look at the light, the water, the temperature, and humidity to find your answer. It could be an imbalance in one or more of these areas.
Keep your seedling environment humid. Growth will slow if the soil/growing medium dries out between waterings. Therefore, it should stay moist (but not saturated) at all times. It’s easier to keep the soil damp with the right relative humidity levels (57 to 67 percent).
Slow growth is also caused by too much competition. Ensure you’ve thinned out small/unhealthy sprouts to give every seedling space to thrive.
Do a careful inspection for disease or pests on each seedling. At this early stage, even minor infections can dramatically stall growth.
Review what lights you are using, what schedule you are following, and where the lights are located. If they are too far away from the plant canopy or not on for at least 16 hours a day, your little starts may struggle to produce enough energy.
When is the best time to transplant cannabis seedlings?
Three to four weeks after sprouting, your tiny cannabis seedlings will be moving into the next stage of life: the vegetative stage.
But don’t rely on the passage of time alone. If your plants are growing slowly due to suboptimal conditions, it may take longer to reach veg.
Instead, look for the development of true leaves. True leaves have serrated edges. Once your plant has four to five true leaves, you know it’s ready to move into a large container.
How much light do cannabis seedlings require?
Give your cannabis seedlings about 16 to 18 hours of light and at least six hours of total darkness a day until they reach the veg phase.
CFLs bulbs, fluorescent tubes, and low-power LED lighting are excellent options for seedlings. In the early days, they didn’t need intense blasting with high-powered indoor grow lights.
Do cannabis seedlings need a humidity dome/propagator?
You only need to use a dome or other type of propagation environment if you cannot otherwise achieve the desired temperature and humidity required by seedlings.
Your growing environment will need to be a stable 57 to 67 percent relative humidity, with daytime temperatures of 65°F (18°C) to 75°F (24°C).
Growing Cannabis from Seed, Learning through Trial and Error
Starting cannabis from seed isn’t always a smooth journey. Cannabis seedlings are extremely fragile and require much more attention than adult plants. But when you get your plants from seed to harvest, it’s incredibly satisfying.
As you learn to grow cannabis from seed, why not get help from the experts? Keep the HydroGuide app in your pocket to guide you throughout every stage, from seedling to veg to flower.