Detailed Overview of Cannabis Fertilizers

Detailed Overview of Cannabis Fertilizers

Fertilization is the crucial factor for indoor and outdoor cannabis production. Research shows that using the appropriate fertilizers, such as organic fertilizers, supplements, and biostimulants, is a vital aspect of marijuana cultivation as they serve as plant food. In addition to stimulating normal growth, fertilizers can also regulate cannabinoid content in plants. It means that they affect the medical and recreational qualities of the buds.

It may be challenging to choose a suitable fertilizer, especially if you are a novice cannabis grower. This marijuana fertilizers guide may help you understand what fertilizers to choose for your weed garden and how to use them properly.

Nutrients Supporting Cannabis Growth

Let’s begin by listing the nutrients that marijuana plants require for normal growth and cannabinoid production. The three most important soil components include:

  • Nitrogen
  • Phosphorus
  • Potassium

important soil components

Research and anecdotal evidence confirm that growers can significantly increase inflorescence yield by regulating the concentration of these nutrients in the growing medium. It is important to understand that more does not necessarily mean better when it comes to these nutrients. A recent study showed that the amount of nutrients should be calculated based on the vegetative cycle. For example, more nitrogen supports vegetative growth, while bud production is facilitated by increasing phosphorus and potassium concentrations in the soil.

Moreover, cannabis also needs a certain amount of calcium, magnesium, iron, and copper. Deficiencies of the listed nutrients can have a significant suppressive effect on cannabis yield, so adding them to the growing medium is an integral part of the growing process.

Types of Cannabis Fertilizers

The first thing to learn about fertilization is what plant fertilizers are acceptable to use with cannabis. Organic options are becoming increasingly popular. These include:

  • Bat guano
  • Wood ashes
  • Blood, bone, soil meal
  • Worm castings
  • Compost

worm castings

Is fish fertilizer good for weed plants? The answer is yes! Similar to blood, bone, and soil meal, it can enrich the soil with essential nutrients for cannabis growth. Organic fertilizers such as this one can help you stay green and decrease the negative environmental effect of weed cultivation. However, they are not as fast-working as commercially produced options and may take more effort to use. Moreover, they are not suitable for hydroponics systems, which require store-bought nutrients containing no organic matter.

Another well-tested approach is to use commercial chemical fertilizers in liquid, granular, or powder form. Chemical fertilizers have precise NPK, micro and macronutrients ratios, making it easier for growers to select the specific type for each stage of the plant life cycle. They are excellent as rescue fertilization when the plants demonstrate nutrient deficiency symptoms.

However, we recommend reading the instructions carefully and avoiding overfertilization that may damage the plants. This is particularly important when you use granular products that are often over-applied. The problem is that these fertilizers are difficult to leach out if you use too much, so it’s easy to cause irreversible damage to the plants. If you are a novice grower, choose liquid products because they are easy to apply and control.

Fertilizers vs. Biostimulants and Supplements

Physical and chemical conditions in the soil may restrict nutrient availability. In such cases, biostimulants can be used to increase nutrient uptake and stimulate the needed physiological processes in cannabis plants. Unlike fertilizers, which provide nutrients to cannabis plants, biostimulants change the way marijuana responds to nutrients. Biostimulants also improve soil structure and root development, which are important for marijuana growth.

Supplements, in turn, improve the physical condition of the soil. They contain a limited amount of nutrients, so they should not be used in isolation from fertilizers as they cannot provide the needed food for the plants.

Marijuana Fertilizer Schedule and Tips

How do you know it’s time to add fertilizers to the growing medium? Researchers note that different growth stages have varying nutrient demands. Therefore, it is essential to track the changes in plant development and meet this demand to improve plant performance. The typical fertilization schedule is pretty simple:

  • During the first week of the vegetative stage, use fertilizers with the 2:1:2 ratio, that is, two parts nitrogen to one part phosphorus to two parts potassium.
  • Change the ratio after several weeks by increasing the amount of nutrients (e.g., use the 10:5:7 ratio)
  • The late vegetative stage does not require much food, so the 1:1:1 ratio is enough.
  • When the plant begins to flower, it no longer needs nitrogen, but you may still add some phosphorus and potassium.

If you find this schedule too tricky, read the packaging, which usually says what products suit each life cycle stage.

marijuana plant vegetative stage

In addition, we prepared answers to other popular questions that arise when growing cannabis.

  • When to use grow fertilizer on weed plants? Growers normally add nutrients when marijuana moves to the vegetative stage of growth. As plants grow large and strong leaves, the amount of nutrients should be increased to facilitate further growth and flowering.
  • What kind of granular fertilizers work to grow marijuana? You can choose quick-release or slow-release options, which differ based on the time it takes for the nutrients to dissolve and get to the plants.
  • Do I need a special fertilizer for outdoor weed plants? We recommend reading product descriptions and choosing fertilizers designed specifically for outdoor use. You may even need no additional nutrients if the soil in your location is suitable for cannabis cultivation.
  • Is it safe to use fertilizers? Organic plant food is completely safe for people and the environment. In contrast, chemical fertilizers and supplements may be toxic and cause skin irritation. Therefore, use personal protective equipment (gloves) and read product labels for more information.
  • Is the cost important? Sure! Avoid low-cost products because they may not have the optimal nutrient ratio and may be dangerous for your health. Talk to the salesperson and choose high-quality options.


Feeding your marijuana is important for a rich yield. With many fertilizers available on the market, it’s easy to select something that suits every pocket, growing experience, and plant requirements. Adjust nutrient levels according to the environmental factors and the growth stage, and you’ll see the results very soon.