Starting Off Right: A Guide to Feeding Cannabis in the Vegetative State

More often than not we tend to focus and worry more about the result of a project instead of paying close attention to the individual steps that are needed to make it happen. It’s common to get so wrapped up in the idea of success that we forget the fact that what is trying to be accomplished will, in the end, actually be the sum of the work it took to get there. By focusing and paying proper attention to each aspect involved, we can ensure that the result is as good as it possibly can be.

To this idea, cannabis is no exception. The goal is a healthy plant with big, beautiful buds. But there are a plethora of steps to navigate before reaching the pot of gold at the end of the rainbow. One such aspect that should never be overlooked or half-assed is feeding the plants during the vegetative growth stage. Taking great care during this stage of the growth cycle will help increase the chances of reaching a successful flowering stage that is worthy of a wonderful harvest.

Nutrients for Cannabis

Like other flowering annual plants, cannabis requires at least 16 essential elements (nutrients), insufficient amounts, to properly develop and reproduce. Three of these elements oxygen, carbon, and hydrogen are accessed through the air and water. The rest must be supplied through the roots via the soil or growing medium.

Depending on soil type, the latter is typically achieved through the application of supplemental fertilization. If one or more of these elements are unavailable or only available in amounts lower than desired by the plant, growth and development will be negatively affected, and the resulting yields will likely be less than if all elements were accounted for.

The 16 essential elements are responsible for nearly every facet of development and their absence will often be visibly noticeable. From the growth of roots and shoots to the development of flowers and fruits, a plant’s ability to have complete and reliable access to these nutrients makes the difference between excellent or poor performance. The elements work within the plant performing nearly every task including the building of amino acids and proteins, creating and storing energy from photosynthesis, as well as the synthesis of life-sustaining enzymes. To be blunt, these 16 essential elements are the workhorse that pushes plant growth along from stage to stage.

Feeding the Cotyledons

When cannabis seeds spout the first leaves are called the cotyledons. These leaves don’t look like the normal leaves, referred to as “true leaves,” which will follow. The cotyledons help to serve as a food source for the growing seedling until the true leaves develop and begin the process of photosynthesis. Once the seedlings have a few sets of true leaves, they can be given light feedings about once a week. Some potting soils come blended with a small amount of fertilizer blended in so depending on the growing medium being used to propagate the seedlings ¼ to ½ strength of a fertilizer’s label rate should be sufficient to keep them growing until they are ready to truly start the vegetative phase. When starting with propagated clones, once the new roots begin to develop the same type of care should be given to them as was given to those that were started from seed.

Caring for the True Leaves

After the young plants have 4-5 sets of true leaves, they are ready to be transplanted into a larger container where they will complete the rest of their growth cycle. The size of the container used will directly correlate to the overall space available in the growing area. Plants that have more space to grow can be grown in a larger container than if the growing area is more constricted. The principal goal of the vegetative growth stage is to allow the plant to develop a strong system of leaves and stems. In this stage, the plant begins to build the necessary structures needed to enter into a vigorous flowering stage. The bigger and healthier the plant can become in this stage, the more successful it will be at developing multiple flower sights that can support heavy flower production.

Vegetative State Nutrition

During the vegetative stage, the plant will require a base nutrient that is higher in nitrogen and lower in phosphorus and potassium. A base nutrient represents the main component of any fertility program (feeding schedule) and should contain the majority of essential elements needed for plant growth. Because of adverse interactions within the formulation itself, most base nutrients will not contain any calcium or magnesium, so some type of Cal-Mag supplement will be required. Most vegetative stage base nutrients available for purchase are labeled with names like “Grow” or “Veg” formula. In this stage, the plants require more nitrogen than any other element for the creation of amino acids and proteins that give the plant a strong structure. On a product label, there is a section called the grade which is represented as N-P-K, representing nitrogen, phosphorus, and potassium. Choose a product that has an N-P-K where the number in the N position is higher than the others (i.e. 12-6-6). Base nutrient products designed for the flowering stage will have a lower N value and a higher P value.

When feeding the plants, it is imperative to start by following the manufacture’s recommended label rates. These will provide an excellent starting point. If the label states a range of feeding rates, it is good practice to start at the lower rates and to monitor over time how the plants are reacting with each feeding. If they appear to react positively, the rate can slowly be increased with each feeding but be careful to not exceed the maximum suggested rates.

From personal experience, I have seen that it is better to underfeed than to overfeed a plant. Problems that arise from over-fertilization are much harder to rectify than those caused by a plant being slightly deficient in an element or two.

There are a couple of things to keep in consideration when determining how often to fertilize the plants during the vegetative stage. The most important is the type of medium being used. A good potting mix that is well-fortified with organic materials and perhaps even some mineral fertilizer will require less feeding than a medium that is more inert such as rockwool. For a standard potting mix, fertilizing once or twice a week should be sufficient. For more frequent feedings the base nutrient should be used at a lower rate since it is being applied more often.

Water Quality

It is also a good practice to use plain water in between feedings to avoid the possibility of excess nutrients accumulating and causing an imbalance of nutrients that can lead to them becoming unavailable to the roots. Another thing to keep in mind is how quickly the medium needs to be watered. Some mediums lose moisture faster than others so the more often the plant is being watered, the more often it will need to be fed.

Beginning a Fertility Program

I recommend, especially for beginners, following the manufacturer’s suggested fertility program or feeding schedule. This is the best way to start on the right foot. After obtaining a good grasp on how the plants grow and react to different nutrient rates then you can start tweaking the program to improve plant development. Indoors, the vegetative stage is typically around 4 weeks from start to finish, not including the seedling stage. Once again, this can vary from plant to plant, and with the space allotted, but 4 weeks is generally about the amount of time the plant needs to develop to a size that can support heavy flowering.

The general rule of thumb is to switch to the flowering stage once the plants are around halfway to the point they should be when fully grown. Also, for beginner and first-time growers, I would recommend only using the base nutrients and Cal-Mag (if needed) for the first couple of runs just to get a good grip on how things work. After you are comfortable with growing through a whole growth cycle, then it’s a good time to start bringing in other supplements like amino acids, humic acids, and seaweeds, to name a few.

Pretty much every single person that gets into growing cannabis first does it because they want to achieve a big, beautiful yield. But it can be a mistake to think that the end game is the only game. Paying complete and nearly exhaustive attention and care to the garden during the vegetative stage is the foremost way to ensure that the plants will be ready for a successful flowering phase. There is no room for cutting corners in the quest to achieving impressive yields.