In this guide, we'll walk through caring for your marijuana plants during the vegetative stage. The arrival of the fully formed seven-point leaves found in mature plants marks the beginning of this phase. The first leaves of a newly-sprouted seedling will have a single point; the next three, then five points; before finally producing the iconic seven-point leaf, which signifies the beginning of the vegetative stage. This phase is where your plant will do a lot of its growth, both vertically and horizontally.
Primary Objective: The objective during this phase is to put on as much plant mass and create as many bud sites as possible while training the plant into the final growth shape before entering flowering. We do this through training, topping and selective pruning. Cannabis plants in the vegetative states are incredibly robust and quickly regenerate from injuries, pests and nutrient deficiencies. Once a plant enters the flowering stage, it becomes much less pliable and robust to manipulation, so use the vegetative state to position your plant to make the most out of flowering.
Optimal Environment: Think late spring through summer, with warming temperatures but decreasing humidity. Along the edge of the forests, the young plants will rustle in the gentle winds as they reach toward the bright sun that shines for 16 to 24 hours a day. Rains come frequently but with time to dry the soil between wettings. The explosive growth needs strong roots to pull nutrients from the fertile soil.
There are lots of options for where you grow, and your selection will depend on your goals and constraints.
Outside - Cannabis can spend their vegetative cycle outside during the summer months.
Space Bucket - These are self-contained environment-in-a-bucket are perfect for single plant stealth grows.
Grow Box - They are a great option for small and stealthy grows for single plant production. You can pick these up premade or make your own or repurpose an old piece of furniture.
Closet - A spare closet can make an ideal grow space because they offer good height and are good at keeping light contained. You will need a fan for ventilation in most closets.
Grow Tent - Grow tents range in size, from 2'x2' (.6m x .6m) on up and are great options for all phases on cannabis life. Tents have great ventilation, reflective walls to make efficient use of lighting and they keep light contained to keep your grow stealthy.
Learn more about grow spaces here.
Photoperiod strains will enter flowering if dark periods exceed 12 hours, so nights must be kept shorter than 12 hours to keep the plants in vegetative growth. Auto-flowering strains, on the other hand, go into flower a set amount of time after germination.
Farmers describe light cycles as a ratio of light/dark hours. Standard options are 18/6 (18 hours of light followed by 6 hours of dark), 20/4 (20 hours of light followed by 4 hours of dark) and even 24 hours of light without darkness.
While the general rule of thumb is that more hours of light means more photosynthesis which means more growth potential, there are indications that dark periods are essential in plant development - particularly in root growth.
Sunlight - Vegging your plant in sunlight is a great option - particularly if supplemented with an artificial option.
Fluorescent Compact Fluorescent Lights (CFL) and fluorescent tube lights can be great options for vegging plants. They are cheap, burn relatively cool and are readily available.
LED - Over the past years, LEDs have overtaken almost all other lighting types for home grows. They are relatively inexpensive to purchase and operate and burn very cool compared to traditional grow lights. In nearly all cases, we recommend LED lighting to other sources.
HPS - High-Pressure Sodium lights are incredibly effective lights and have been successfully used to grow amazing buds for decades. They do burn hotter than LEDs, which can cause temperature problems in tents and other confined spaces.
Learn more about lighting options and schedules here.
With vegging plants, we are trying to replicate summer conditions. Ideal temperatures are between 70 and 85F (21C-30C) and should not go above 90F (32C) or below 60F (15C). Vegetating plants need less humidity than seedlings since their mature roots can pull ample moisture from the soil. Increased humidity runs the risk of mold, rot, and pests, so keep the relative humidity around 50%. For optimal conditions, start vegging at 60% and lower to 45-50% through vegetation.
For watering, vegetating plants follow the same rule as all other phases:
DO keep the soil warm and moist throughout the vegetation phase.
DO NOT flood or saturate the medium, since this will prevent the roots from getting enough oxygen. Too much water and the seedling will suffer root and nutrient problems and eventually fail.
A good rule of thumb is to wait until the top two inches of medium (knuckle deep) is dry before watering again. Another method is to gage from the weight of the bag. If you see the leaves start wilting, you've waited too long. Have no fear though; young cannabis plants are amazingly robust.
Vegetating plants need macro-nutrients for basic building blocks in its rapid growth process. During the vegetation phase, nitrogen is essential and phosphorous is less critical - though those roles reverse during flowering. Vegetating plants need micro-nutrients too, like iron, calcium, zinc, etc. Too many micro-nutrients can block macro-nutrients. Most nutrients are only available to the plant at specific pH ranges. Using balanced multi-part nutrient systems are the best mechanism to assure your plants get what they need.
Since nutrient requirements and tolerance can vary by plant, it's a good idea to calibrate the needs of each plant. Start off with around 1/4th recommended dosage and then gradually increase until you hit the right level. The bottom leaves will begin to yellow if there aren't enough nitrogen and leaf tips will burn if there are too many nutrients.
Learn more about watering and nutrients here
The key to effective pest control is to be proactive before there is an outbreak. Pests thrive in the same conditions as your plants, so it is inevitable that they will find your crop if you don't take steps to prevent them from establishing a foothold in the first place. Whether it's mites, mold or whiteflies, there are a few preventative measures that can help you keep your crops safe:
- Keep it clean; don't leave litter, rotting leaves or standing water in your grow space since this provides excellent hiding spots and food sources.
- Don't spray the plants right before lights out; water droplets left on the leaves can encourage mold and mildew.
- Keep proper temperature and humidity; too warm and humid and pests will thrive.
- Use neem oil treatments at least once a week to make it more difficult for pests to gain a foothold.
- Treat outbreaks aggressively
Plants in the vegetative state heal faster than plants in the flowering stage, so it's a good idea to make sure you have pests under control before transitioning to flower.
A small plant in a big pot causes problems because it is difficult to get the correct mixture of water and air for the roots. A large plant in a small pot with drastically slow growth. Start plants in an appropriately sized container and then transplant vegging plants as they outgrow their current container. Make sure that they are in their final container before starting to flower.
Learn more about containers and transplanting here.
Training & Pruning
Vegetating cannabis grows rapidly; we call it weed for a reason! Since our primary objective in the vegetative state is to get into the desired shape, this is the time to get the plant into a shape that will best take advantage of your grow space. There are a variety of techniques available to manipulate vegetating plants.
Why do I want to train and prune?
Cannabis plants naturally grow into a shape similar to a Christmas tree. Some cannabis strains can grow 20 feet (6 meters) in just a few months. Growing plants that size won't work for most home grows, so we use a variety of techniques to shape the plant to optimize for the space available.
Low-Stress Training (LST): A mechanism for engineering cannabis growth by gentle and persistent manipulation of growing shoots through bending and shaping. It does not involve cutting, breaking, damaging or performing other stressful activities to the plant. The goal of LST is to develop the plant for optimal flower production later in life by continually pulling the tallest vertical branches and securing them to grow horizontally. Training the plant's side branches to grow horizontally produces a flat canopy to make efficient use of indoor lighting.
Learn about how to combine topping and LST to boost your crops in our Low Stress Training guide.
Topping & FIM'ing: A mechanism that involves cutting or pinching the growing tips of the cannabis plant to break apical dominance and encourage branching. Apical dominance is when the principal, central stem of the plant is dominant over other side stems. Apical dominance causes cannabis to naturally grow in the traditional Christmas Tree shape with one large bud at the cola and smaller buds on side branches. Its an excellent form for growing cannabis under the sun (large light source far away) but does not work well for indoor lights (a small light source close up). Breaking this dominance allows multiple large colas and a flatter surface area for more massive indoor production. Since topping can stress to the plant, it can slow growth for a few days.
If you are growing an auto-flower with a short veg cycle, you will probably want to skip topping and rely on LST techniques.
Learn more about Topping & FIM'ing here..
Super-cropping: Another HST technique that increases yield and potency and encourages bushier growth. With super-cropping, the main stem is twisted and damaged in a specific way, so that when the plant regenerates it with improve vascular capabilities and some theorize that the stress can cause the plant to produce additional THC as a defense mechanism.
Pruning: Pruning is a hotly debated topic in cannabis circles. Some people claim that it harms the plant to remove fan leaves, and you should instead remove bud sites that aren't getting enough light instead. We have found that both are helpful:
Pruning excess leaves can reduce humidity and improve airflow
Pruning branches and bud sites from lower on the plant, where they receive less light and would never develop past the pop-corn size anyway, divert resources back to buds on the top.
If you choose to prune, try to avoid mass pruning as that can cause stress and even shock that will slow the plant's growth. Instead, remove a few leaves or bud-sites at a time. Look at it as a continuous process throughout the veg state.
When Is The Vegetative Phase Over?
In photoperiod strains, the vegetative stage lasts as long as the plant gets less than 12 hours of uninterrupted darkness per day. In nature, this continues from spring to early fall. Plants will begin the flowering stage after nights lengthen to 12 hours of continuous darkness. Indoor growers can end the vegetative stage and start flowering by setting the light schedule to 12/12 (12 hours of light followed by 12 hours of uninterrupted darkness). Controlling the light cycle allows you to decide, based on space and goals, to determine how long to vegetate your plants.
Autoflowering strains, on the other hand, begin flowering after a set number of days from germination regardless of the lighting schedule. The advantage is that you don't have to worry about lighting schedules as much, but you also lose some control.
What's wrong with my plant?
Sometimes things don't go the way you planned, and it seems that no matter how careful you are, things are going to go off the rails with cannabis sometimes. Luckily, vegetating plants are very robust and most common problems are are easy to diagnose and simple to fix.
Nutrient deficiencies are common in vegging plants, especially nitrogen deficiencies. Often caused by pH balancing problems, and not a lack of nutrients in the medium, these are simple to diagnose and easy to correct.
Mite, mold and other pests can also wreak havoc on your crops. Luckily, these are easy to treat in the vegetative state, and there is plenty of time for your plant to recover before you put it into flower - unless it's an auto-flower.