The United States has legalized the cultivation of cannabis in 10 states producing more than 60 million marijuana plants valued at over 60 billion dollars yearly. Cannabis fertilizer plays a key part in increasing the yields and weight of harvest for these growers.

Major Nutrients of Cannabis Fertilizer

Cannabis requires a heavy amount of nutrients to support bud development, particularly in the plant’s flowering cycle. Nitrogen is needed primarily during initial growth stage (vegetative growth), while Phosphorus and Potassium are required increasingly as the female plant structures it’s seedless bud flowers, otherwise known as sensimilla.

A variety of commercial fertilizers are used to provide the required nutrients to cannabis plants. On the front label of these fertilizer, three numbers are clearly defined – N, P and K. For example, 12-24-24. N, P and K and the major nutrients used by plants to support growth.


N (Nitrogen) Nitrogen , the gaseous element, is needed by cannabis plants to help support the vibrant green new growth of foliage - shoots, stems, leaves and stalks. Cannabis plants supplied an adequate amount of nitrogen display a healthy green-colored appearance, while conversely, plants starved of nitrogen present themselves in a yellow, drooping manner.

Nitrogen can be applied in the form of high nitrogen fertilizers, urea, ammonia, and natural sources such as high N leaf litter.


P (Phosphorus) The solid element Phosphorus, aids the marijuana plant’s structure, including the stems, branches, buds and leaves. The availability of P in the soil is often low, due to the element’s nature of clinging to “magnetic” heavy clay particles. Cannabis plants given a healthy supply of absorbable phosphorus are able to bulk up in weight, providing the grower a heavier harvest. Conversely, plants low in phosphorus tend to show signs of weakness and yellowing.

Phosphorus is supplied to plants by the means of high PK fertilizers. Rock phosphate is the primary synthetic derivative of P. Organic sources include manures and animal parts.


K (Potassium) The solid element has intricate relationships with cannabinoids and terpenes. The sugars of the cannabis plant, found in the large maturing buds, are affected by the amount of potassium absorbed by the plant. Anecdotal evidence by growers describe the flavor and sweetness of buds increased with adequate potassium application, along with heavier yielding big buds in the plant’s flowering cycle. Devoid of enough potassium, the buds of the cannabis plant remain stunted in growth and yield impaired.

Potassium fertilizers can be added to cannabis plants in the form of potash, muriate of potash, sulphate of potash, along with natural organic sources like kelp meal and manure.

Minor Nutrients

Ca (Calcium) promotes thick cell structure in marijuana buds and increases the bud density during flowering cycle. Calcium nutrient additives include crushed coral and dolomite lime.

S (Sulfur) aids in the creation of various plant enzymes, along with amino acids and proteins required by the cannabis plant for growth. Sulfur is added to plants via high S fertilizers, which are oxidized sulfate.

Mg (Magnesium) is required by the plant for the production of chlorophyll. Anecdotal evidence shows that magnesium is a key component in increasing the density of buds. Magnesium sources include dolomite lime.

B (Boron) is an element used by the marijuana plant along with calcium to aid in the photosynthesis process, along with cell division. Most bestselling cannabis fertilizers have adequate amounts of boron.

Fe (Iron) plays a role in photosynthesis for the cannabis plant, however Iron is needed in only small quantities. Iron sources include micronutrient fertilizers, along with rusting iron metals.

Cu (Copper) aids plants in a variety of enzymatic processes. Copper sources can be used as the raw metal material, along with synthetic derivatives of the nutrient element.

Other micronutrients required by cannabis for growth in small quantities include:

  • Cl (Chloride)
  • Mn (Manganese)
  • Mo (Molybdenum)
  • Ni (Nickel)
  • Zn (Zinc)



The Top Recommended Fertilizers for Cannabis

Commercial synthetic and organic fertilizers are used by cannabis growers to supply the needed nutrients to plants. Refer to this list of the Top 10 Best Bud & Bloom Fertilizers for recommendations. The specific plant fertilizer application ratios are dependent on the stage of the cannabis plant’s growth cycle.

Vegetative Growth

Typically, during the beginning stages of plant growth, a fertilizer diet rich in Nitrogen is used to maximize vertical and horizontal growth. Phosphorus and potassium are also used in adequate doses, although not as heavily.

Standard fertilizer ratio 3:1:1

Flowering Cycle

While the marijuana plant is flowering, higher doses of PK are used to promote bigger buds and larger yields. Nitrogen is still used, however in smaller quantities. Micronutrients are also crucial to flower bud development.

Standard fertilizer ratio 1:3:2


The schedule by which growers feed their marijuana plants is defined by the amount of available nutrients currently in the soil-root medium.

For example, an organic mix loaded with various nutrient sources contains a constant supply of these nutrients for plants to absorb, so excessive fertilization may be avoided. Conversely, plants grown in sterile root mediums require constant feeding to supply the plant a balanced diet of nutrients, in the form of water-soluble fertilizer.