Grow Room Environment…
When in the vegetative stage the light cycle should be 18 hours on and 6 hours off. Having your lights on throughout the night time makes it easier to keep the growroom cool as the ambient temperature is lower.
Plants in the vegetative stage perform best under Metal Halide lamps, but High pressure Sodium lamps will still do a good enough job. Dual spectrum bulbs are a good investment as they work very well throughout both the vegetative and flowering stage.
A 400watt lamp should be kept 30cm(1 foot) away from the plants canopy. A 600watt lamp should be kept 45cm(1.5 foot) away from the plants canopy. A 1000watt lamp should be kept 60cm(2 foot) away from the plants canopy. A good method to make sure the distance form light to plants is ok is by putting the back of your hand underneath the lamp for 30 seconds, if it’s too hot for your hand it’s too hot for the plants. For more on how to position your light check out the Light Spacing guide on this site.
While the lights are on the room should be 25-27ºC, while the lights are off the room should be 20-22ºC.
The humidity of the room should be around 65%.
The grow room will need 1 medium sized oscillating fan(around 12-16 inch) for every 2 lights used, the fan should blow in the gap between the lights and the plants canopy, do not blow a strong wind directly at the plant as this will cause the leaves to dry out and slow down growth. Just a light breeze swaying all around the room is what the plants like best.
An intake fan and an exhaust fan with enough power to completely exchange all the air in the room within 5 minutes. A 5 or 6 inch exhaust fan(depending on model and heat being produced) per 2 meters squared(2 400 or 600watt lights) with a suitable intake is usually adequate.
It is very important that your exhaust fan with a carbon filter connected can move more air than your intake fan to create a negative pressure in the grow room. If the intake fan brings in more air than the exhaust can take out you will 100% have issues with the smell of weed escaping the room for anyone and everyone to sniff out. A carbon filter will reduce the amount of air a fan can move by 30%, take this into account when measuring the CFM ratings of the 2 fans. A fan speed controller can be used to ensure the correct temperature and a negative pressure is maintained. I advise you to spend a little extra money on a good quality carbon filter as a cheap budget filter will not fully clean the air that passes through it, although plants don’t smell very much in the vegetative stage i still believe a good carbon filter is necessary throughout all of the stages just to be safe.
Feeding Your Plants…
When it comes to buying nutrients for your marijuana plants in the vegetative stage i advise that you stick to the same brand with each product that you buy, for example, your A+B should be from the same company as your PK 13/14. Each nutrient company should supply a feed chart for their range of products, the hydroponic shop where you buy your nutrients from should give you one if you ask, if not you can search on the internet for a feed chart matching the brand you have. Never mix nutrients directly togethor, you always need to have the desired amount of water in a bucket or water drum then add each nutrient to it one by one.
If you decide to grow hydroponically it is essential that you get a PH tester, PH up and PH down. Although coco and soil are more forgiving, but expect a reduction in yield if you do not adjust the PH of the nutrient solution. The PH of a hydroponic nutrient solution should be 5.6 – 5.9, the PH of the nutrient solution for feeding soil or coco should be 6.0 – 6.4. A plants roots can’t uptake all nutrients and minerals to the full potential if the PH is not within the correct range. PH adjustments must be made once all the nutrients have been added the the water, in hydroponic systems the PH will need to be adjusted every day or two.
At the beginning of the vegetative stage a plant will need around 250ml of nutrient solution each day, towards the end of the vegetative cycle the amount of nutrient solution each day will depend on how long you have vegged for, the size of the plant, it’s root system and the temperature of the room. A plants need for hydration will increase rapidly as it grows, you will learn how much water you are going to need as each day goes by. If you are using soil or coco you can visually inspect the medium and pick up the pot to see how heavy it is, if the pot is dry and light then you know you need to feed the plant. In soil or coco you should feed the plant clean water once every 7 days to flush some of the excess salt build up out of the mudium. In hydroponic systems it’s as simple as topping up the reservoir as it empties, a hydroponic nutrient solution will need to be fully drained and replaced every 7 days to avoid inconsistencies in the nutrient solution, if you don’t do this your plants will eventually run into some serious health problems.
Here is a vegetative stage feed chart i drew up for using House & Garden products.
Transplanting Your Seedling or Clone…
Around 24 to 72 hours after the seed has been planted it should start to show its first signs of life by emerging to the surface where the shell of the seed will fall off leaving a tiny set of leaves to absorb light and begin to grow. Your plant will now need to be transplanted into a pot or a hydroponic system, to do this simply fill your plant pot or net pot with the meduim you wish to use, in the centre of the medium create a hole just big enough to bury the cube that your seedling is planted in. Put the plant into the hole then fill around the edges so the cube is anchored into place, cover the cube with medium as soon as the plants stem is tall enough to keep the first set of leaves about 2cm above the medium.
The Vegetative Stage…
A weed plant should be given access to 18 hours of light per day as soon as it emerges to the surface, if you are using clones they will already have been in 18-24 hours of light per day while they were rooting and will need to recieve 18 hours of light per day once rooted and potted. Keep hot HID grow lamps very high up so that there is no direct heat at all on the plant as they can burn very easily at this young age. After around 7-10 days you should lower the light(600watt) until it is about 45cm away from the plant, you will need to move it up as the plant grows into it. A good idea is to tie a peice of string to the lamp shade that is 45-50cm long with a weight on the end so that you can easily keep the correct distance from light to plant.
A good vegetative stage is one of the most important parts to growing cannabis as this is where a plant is prepared for it’s flowering cycle, the better you prepare a plant the more bud it will be able to produce during the flowering cycle. I believe that training and manipulating the plant so that it’s wide and bushy is the best way to get it to produce as much high quality bud as possible. I advise you to learn a method known as SCROG or Screen Of Green. The SCROG method is where you top and bend the plants branches into a horizontal netted screen to create an even flat surface in order for your light to penetrate effectively on every shoot. A simple way to do this is to top the plant as early as possible and keep doing this all way through the vegetative stage. You should have your horizontal netting placed above the plant at around 1 – 1.5 foot higher than the base of your main stem(any higher can become unnecessary), the best way to do this is to build a table like frame from some wood or PVC pipe and put your net across the top of it. You should aim to fill 75% of the screens width before you change the light cylce from 18/6 to 12/12. The plant will fill the whole screen within the first 14 days of the flowering cycle(12/12). You can do this with as little as one plant and still achieve the same yield as you would if you had used 4, although it may take a little longer to grow only one plant per light it allows you to reap high yields while keeping the number of plants as low as possible. A bubbler pot system is the most efficient system to use when growing a small number of large plants, this is because the vegitation stage can be completed nearly twice as fast as it would if you were to have used soil or coco. If you do happen to do the SCROG method while using soil or coco you will need to take into account how big your root system will get. The bigger the root system the bigger the yield. So how long is the vegetative stage of a cannabis plant? As long as it takes to fill 75% of the width of the space you intend to fill.
A method known as SOG or Sea Of Green is the fastest way to get through the vegetative stage. The SOG method is where you put a large number of small plants under one light so that you can switch to the flowering cycle as fast as possible. When doing an SOG grow it’s sometimes possible to put the plants straight into flowering without any days of vegetation at all, but it’s usually better to be safe and have around 5 days of growth before switching to the 12/12 light cycle. The SOG method works very well when 16 plants or more are spaced evenly over a 4ft x 4ft space under a 600watt HPS light.