Vegetative Stage

Back to How to Grow Weed
Both photoperiods and autoflowering will thrive under a full 24 hours. The Marijuana Horticulture Bible (pg. 38) states that this is the best light schedule for vegetative growth.

A seedling will typically emerge out of its medium anywhere from 4-14 days, usually sooner rather than later. But they can take awhile, and this why a lot of growers like to germinate with a paper towel because they will seed the taproot emerge typically within 48 hrs. And if the taproot shows, then the plant will most likely develop into a seedling. Be careful not to damage the taproot as it's the plants only source of life.

When the seedling pops you’ll probably see 4 leaves, 2 large oval-shaped ones, that look like the shell of the seed (called cotyledons). These feed the seedling until veg, so no need to give nutes yet. You’ll also probably see two tiny fan or “true” leaves.

Cannabis typically stays in the seedling stage for about 2 weeks. They are in veg when the leaves have developed into the classic 5 finger leaf.

High humidity and temps in the 70’s is the best range for seedlings since it’s supposed to be spring.

Most growers germinate their seeds in a starter cube or seedling plug. Some growers use the wet paper towel trick or just simply plant their seeds into the medium that they will use for veg and/or flowering.

For beginners I recommend trying out the Propagator Kit, It comes with everything you need to give you a headstart with tools to aid you with transplanting your seedlings into your prefered grow medium.

Inside growers can keep their plant in a veg stage for as long as they desire. Most growers have a general height they want to get out of their plants and with some background knowledge on the strain they can guess the final height pretty easily. 3-4 weeks is the usual veg period.

When growing outside the season/time planted will decide how long vegetation lasts and the plant will naturally switch over.


I’ve talked before about how growing indoors is trickier than growing outside because plants are a bit less stable due to the artificial environment. But what’s nice is this becomes a bit of a wash since it’s much easier to monitor and take care of your plants since they’re accessible whenever the lights are on (which you dictate).


Daily care is super easy when growing outside. You’ll want to keep track of watering, feeding nutrients, providing light, watching temps, and making sure there is stable wind circulation.

While planting in the ground is great, I personally still like using a grow bag for a few different reasons. The biggest is that I can move my plants around and that just makes things super convenient and helps me avoid common grow issue. This makes it easier to keep the plant from getting drowned by heavy rains. You can move it around and capture more sunlight, and get it away from bugs.


There are three light schedules you can choose when growing in veg. For photoperiods, the majority give their plants an 18/6 light on/off schedule. Though 20/4 is gaining more traction and I’ve had great results from it. For autoflowering strains, growers seem evenly divided between 20/4 and a full 24 hours of light.


It’s recommended to place plants outside in the spring. You’ll want to make sure not to take them outside when there is 12 hours or more of darkness. And it completely fine to start growing them inside to give them a head start.

Both photoperiods and autoflowering will thrive under a full 24 hours, and Marijuana Horticulture Bible (pg. 38) states that this is the best light schedule. Though some growers like giving their plants some time off from the light and feel that their plants are less stressed.

Ed Rosenthal who is widely considered to be a growing guru recommends 24 hours of light and backs this will how cannabis plants photosynthesize.

“Marijuana plants photosynthesize as long as they receive light as well as water, air, nutrients and suitable temperature. Photosynthesis is the process in which plants use the energy from light (primarily in the blue and red spectrum's) to combine carbon dioxide (CO2) from the air and water (H2O) to make sugar while releasing oxygen to the air. Plants use sugars continuously to fuel metabolic processes (living) as well as for tissue building. The plant combines nitrogen (N) with the sugar to make amino acids, the building blocks of proteins. They are the substance of plant tissue. When the light is off, the plant's metabolic processes, respiration and growth, continue. The plant can photosynthesize continuously so it produces the most energy and growth when the light is on, continuously. Continuous light does not stress the plant, which reacts somewhat mechanistically to it. Plants under an 18-6 light-dark regimen are producing sugar only three quarters of the time. They are thus growing at only 75% of their potential. Leaving the light on continuously will result in bigger plants, faster, which leads to higher yields."

The question becomes do cannabis plants need darkness to rest and for other processes other than growing because most growers don’t see a full 25% increase of growth with 24 hr. It’s ultimately up to you and the strain you’re growing. I recommend to try different ones out and find the best. If you’re concerned about a high electric bill having an 18/6 will save you more money than a full 24 where you not only have the lights running, but a cooling system to remove heat.

Eventually, when growing you’ll probably look into plant training techniques and while you probably won’t do any for your first grow it’s good to familiarize yourself with them now.
Plant training is a catch-all term for a number of techniques that aim to train the plant to stay short and grow more horizontal. Remember when I said you’d come to find out that cannabis is a super-adaptive plant? This is one of the big things I was referring to.

Growers will do everything from gently pulling down the stems with ties at an angle to force the plant to grow horizontally (Low Stress Training). To deliberately cutting off and removing parts of the plants to increase bud sites and to control which direction the plant grows (Topping and FIMing).

Growers do this for two reasons. The first is it keeps plants short. Cannabis plants, especially sativa strains, can grow to incredible heights with some strains easily towering over people. Most strains have been breed, however, to stay under four to five feet on average. This might not seem like a lot but once you add the lights over top and a container for roots underneath a 4-foot plant may need a 6-7 foot grow tent. Training done right can easily lower a plant's height by at least a foot.

The second reason is this creates a canopy allowing light to hit multiple buds sight with a lot of light instead of one bud site getting the majority. Simply put; the more light coverage a plant gets the more buds it’s going to produce.

It might seem like removing parts of the plant is bad for its health and it is! But only temporarily and when done right the plant rebounds back stronger. Kinda like how a bone is stronger after it broke. You mainly do plant training in veg because with photoperiods you can keep them in veg for as long as you want, giving them ample time to recover. With autoflowers, it’s recommended to not remove parts of the plant.

But, despite what some will say, LST is fine for both autoflowering and photoperiods during any stage after seedling. I personally think, and several other growers would agree with me, that minimal LST causes no stress whatsoever. Don’t start LSTing until the plant is around 5 inches. I would look into LSTing even for your first grow.

Common Cannabis Training Techniques:

- Low Stress Training (LST)
- Supercropping (Extreme LST)
- Sea of Green (SoG)
- Screen of Green (ScrOG)
- Intro to Cutting Your Plants For Better Growth
- Main-Lining (Creating a Manifold)
- Defoliation (Advanced Only)
- Topping
- FIMing

We talked about how you want at least 18+ hours of light and you’ll want watch to your temperatures both when the lights are on and off. It’s best to keep your vegetation temps between 70-85°F (20-30°C).

Cannabis is a hardy plant and can briefly tolerate temps outside this range. In my early days, I fought with heat a lot and had temps that hit the high 90’s for several hours. This was in flowering too, which has a lower temperature range to help trick the plant into thinking it’s fall.

It’s completely fine if you’re daytime and nighttime temps are the same. Some strains, like Blue Mystic, produce a lavender hue on the leaves during flowering, but will only do so if night temps are decently lower than the daytime temps.

A light breeze over the plant helps strengthen the stem (this is necessary for holding the heavy weight of the colas). As well, it circulates stagnant air from building up, which can cause high humidity (which needs to be avoided in flowering to prevent mold). Last, it can keep pests off your plants which is something that you can experience when growing indoors.

Air circulation is important for controlling humidity and because plants need to breathe just like us.

Air circulation is also great for preventing hot spots, where the direct light on the plant builds up. You want about enough air circulation that your plants leaves gently move as if there was a natural breeze. Too much can actually damage your plant and “wind-burn” it, but the right amount will strengthen the stem which is very important. Also, make sure that you’re both introducing and exhausting the air with fans.

Humidity is just the percentage of how much water is in the air. The higher your humidity the less water you’ll need to provide as the leaves will absorb the water molecules in the air. Some growers will even feed their plants this way by spraying their plants, and interestingly enough, it appears that a plant’s stomata won’t close even at night if humidity is high enough.

Optimal range should usually be 40-60%. Optimal humidity for seedlings and plants in veg won’t be as critical as later stages, but low humidity may lead to the stomata closing even when the lights are on, which could damage the plant’s photosynthesis process.

Open stomata are what allow the plant to take in gases, such as carbon dioxide and oxygen. Carbon dioxide is needed for photosynthesis, while oxygen is needed for respiration. Stomata close at night to protect from water loss (plants lose water when their stomata are open), but this doesn’t need to happen if there is a lot of water in the air.

Seedlings: 60%+
Vegetation: 60%+
Flowering: 50% and less (The lower the better)
Drying and Curing: 60% on the money.

A low humidity in veg isn’t the worst thing. You’ll want to make sure you’re watching your watering since she’ll dry out faster. Your plant will probably be a little more fickle if she has low humidity in veg.

There is also a relationship between humidity and temperature. If your temperatures drop, but the vapor content in the air stays the same, your humidity rises; if temps rise then humidity drops. This is obviously the opposite of what we want to happen since we want both lower temps and humidity in flowering.

Since this relationship that we don’t want occurs, I highly recommend a dehumidifier. Raising humidity is not terribly hard because you can just lay some pots filled with water in your grow tent. That way when the water evaporates it says in your tent. Be careful to not have any loose wires and things like that around since you have standing water.

Some growers attempt to get their humidity as low as possible the last week or so of flowering to increase trichome production, but I don’t know if that helps or not.

Pure H2O is 0 parts per million (PPM), but your tap water has other chemicals in it. You have 3 main types of water.

Tap/Mineral Water
You’ll see a lot of debate over this, but I think tap water is completely fine to use as long as the ppm isn’t outrageous. In my opinion, if your tap water ppm is over 300 you might run into some issues, especially when you’re in the seedling stage. My tap water has always been under 250 ppm and it’s usually easily under 200 ppm and I never had an issue. When watering with tap just make sure to let the water sit out for a couple days, so the chlorine can evaporate off. Don’t boil your water to evaporate the chlorine, because while it works, you also lose water while retaining all the salt.

Spring water
I would personally just avoid buying this as the ppm vary from brand and it will get stupid expensive fast.

Pure/Distilled/Reverse Osmosis
RO (reverse osmosis) water is what most professionals use and it’s created by running water through a reverse osmosis device (Not to be confused with the filters that fit your drinking facet). This water is completely pure and will have a ppm of 0 or damn close to it. Distilled water is just another term for it and you see it sold in grocery stores. RO filtration systems are quite expensive, with basic ones starting around $100 and good ones around $200. Though that is a whole lot cheaper in the long one compared to buying distilled water. This is the best water hands down to use, but most beginners that want to save money should try/test their tap water first.

There two tricks for knowing when your plant needs water. Unfortunately, these don’t work for gauging seedlings. But seedlings are pretty easy to water and really you just want to aim for the top always being slightly moist. The root system is probably around the same size as the plant so just imagine the seedling flipped upside down and think about how much water would be needed to surround it. 

Two methods to determine when to water
1: After watering don’t water again until the top of the soil is dry, which is about an inch or two down or up to your first knuckle. I used this method in the beginning and preferred it until I became more comfortable with method two.

2: Feeling the weight of the container. Watering will cause the container to become much heavier than when it’s dry, which is good for the plant. You don’t want your grow medium to always be saturated. This is another reason I recommend a container when growing outside. I think it took me until my third or fourth grow before I completely switched to this method. And it develops naturally because my friend would use that method and I just couldn’t understand how when I was on my first grow.

How much do we water
The general rule of thumb is to keep adding water to the container until you see get at least 20% runoff draining out the bottom of the pot. Your plant will drink more depending on where you keep your temps and how high the humidity is. It’s easier to overwater in soil than it is in a soilless medium like coco coir, which when mixed with perlite makes it almost impossible to overwater.