Vegetative (or veg) is the time in a plants life when it needs more (N) Nitrogen and (K) Potassium and at least 16 hours of uninterrupted light so that it can grow strong and quickly. Cannabis plants in the vegetative stage prefer a environment that maintains a slightly higher humidity that is set at a slightly higher temp compared to Flowering (in order to speed up growth and vigor) keep the humidity slightly higher (around 60%).
Once your plants have sprouted, they enter what we call veg, where hopefully they will become big and strong before you decide to switch them to flower (12/12)in just a few weeks time.
The veg stage will last on average 4-6 weeks indoors for most cultivators because we only want the plants to reach a certain maximum height. (Most cannabis plants, once moved into the flowering stage will almost double if not triple in height) In general, the longer you wait, the taller the plant will become which in turn will produce a higher yield but there is certainly a point of diminished returns at which waiting any longer can actually reduce yield because the lights can only penetrate so deep into the plants but for the typical grower 4-6 weeks is usually
As your cannabis plants grow larger they will begin growing horizontal branches and full will begin to fill out. You may begin to notice signs of sex showing up at the very top nodes, but in general you will not be able to sex your plants until you decide to switch them into flower.
If you choose to build a good quality super soil that is already packed with nutrients, (do not use time release soils) you should not need to add any nutrients for the first couple of weeks or at all! A lot of newbie growers over fertilize and this can end up burning or locking out other nutrients from the plant. Be careful if you are using mineral salt nutrients and follow the directions that come with the product. Usually it is a good idea to give the first feeding at half the recommended dosage and then build onto that if needed.
Your primary aims at this stage are to water them and provide them with light and Co2. (Just make sure you let your soil almost dry out between watering)
Once your cannabis plant is about a third to half as tall as you would like it to be, preferably with 4-6 nodes, you can begin the flowering stage That’s probably about 4 weeks to get the best combination of factors.(for the typical indoor grower)
Blue Spectrum (i.e. fluorescent, metal halide, LED)
Throughout this veg stage, you should be using lights that are sufficient in the blue spectrum range. Look for daylight bulbs and if the package displays color temperature, you want 6,500K. Now there are HPS bulbs on the scene that have dual spectrum’s, meaning they are able to provide the right type of light during both stages of growth, this is what the majority of cultivators choose.
The lights during veg should be on for at least 18 hours and off for 6 hours, which is achieved with the help of a decent timer (as seen above), tho it is certainly possible to veg with 20 hours or even 24 hours of continual light. Pick a sunrise/lights on time and try to keep this the same throughout the entire plant’s life.
Try to keep your garden in complete darkness when the lights are off as light leaks can increase the chances of hermaphrodites (having both male and female parts). Particularly if you are not using top quality seed stock.
If you are only using CFL’s or fluorescent tubes, you should place the lights within a couple inches of the tops of the cannabis plants. They can be practically touching the plants as these lights do not produce much heat at all but 2-3 inches or so away is ideal. If your lights are too far away, it might cause your plants to stretch for the light and stretching is usually detrimental to the growth, giving weak stems. For the best yield you want thick, strong plants, not tall lanky ones.
Keep a thermometer in the room and monitor the temperature. While the lights are on, the temperature should be between 70-80 degrees Fahrenheit. During veg most aim to grow their plants at 78F which can speed up new growth. During darkness, the temperature will obviously drop but we don’t want it too cold, ideally this drop will be less than 15 degrees(F).