This may seem a bit confusing for new indoor growers, as they may think they are providing more than enough light to their plants. But consider the following: Positioning a 200W metal halide (MH) bulb relatively far from the pot will be less effective than a 20W CFL bulb placed a few inches from the leaf surface. Even though CFLs are much weaker than MH, light intensity drops significantly the further away plants are from the source.
Note: Some growers try tying their stretchy seedlings to a stake. We do not recommend this method, as it doesn’t do anything to combat the weak, overgrown stem or the difficulty it’ll present further along in the grow.
What Causes Abnormal Stretching?
Long, stretchy stems are one of the most common problems growers face during the seedling stage. Luckily, there are a few simple ways to prevent and fix stretching in cannabis seedlings.
To meet these requirements, we recommend using one 12W CFL bulb per 1–2 seedlings. Keep the bulb 5–7.5cm (2–3in) from the top of the seedlings and monitor their growth carefully, making sure the plants don’t make contact with the bulbs.
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.
At this stage, the plant is vulnerable to disease and mold. Keep its environment clean and monitor excess moisture. Be sure to give it plenty of light.
Once your seed has germinated, or sprouted, it’s ready to be placed in a growing medium, like soil. The tap root will drive down while the stem of the seedling will grow upward.
Seedling stage length: 2-3 weeks
If you’re growing indoors, you can force a weed plant to flower after only a few weeks when it’s small, or after several weeks when it’s big. If you’re growing outdoors, you’re at the whim of the seasons and will have to wait until the sun starts to go down in fall for it to flower and then to harvest.
Harvest happens sometime between September and November. This depends on your local climate, as well as the weather that particular year—one year it could be the end of September, the next, end of October, and growers in the Pacific Northwest will have to pull down their crops earlier than those in Northern California.
Marijuana light cycle: 12 hours a day
The biggest variability in how long a marijuana plant takes to grow will happen in the vegetative stage—after the seedling phase and before flowering.
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Luckily, unlike some of the other seedling issues we’ve mentioned in this post, it is possible to remedy nutrient burn. Simply lay off the nutrients for at least one week and water your plants with plain, pH-balanced water. Once your plant starts to grow more healthy, green foliage, slowly dial the fertiliser back in.
STEP 2: USE THE RIGHT GERMINATION TECHNIQUES
Cannabis seedlings like daytime temperatures of 20–25°C and nighttime temperatures that are roughly 4–5°C cooler. High temperatures will stress your seedlings and stunt their growth, which, at such an early stage, can prove fatal. Dry leaves with curled up edges are a telltale sign of heat stress. With time, your seedlings might also develop other symptoms, including pale foliage and red or purple stems. Heat stress can also cause weak, wilting leaves with downward folding tips.
Most blogs and forums will tell you that your plants are ready to veg after two weeks, but that’s far from true; it usually takes about 3–4 weeks from germination for your seedling to use up all the energy stored in the seed, although some plants develop faster than others. But rather than going by time, we recommend you transplant and start vegging your seedlings once they’ve developed at least three nodes and 4–5 sets of true leaves.
As the name suggests, white powdery mildew is a type of mould that forms as a white, flour-like powder on the leaves of your plants.