How Often Should I Fertilize Cannabis Plants

What to feed my plants, and how much? It’s a hard question to answer and you will get different information based on where you look and who you ask. If you ask the large nutrient manufacturers, they will point you at an expensive, multi-product line and suggest you feed your garden as much as you possibly can without killing your plants. If you ask an earth-mother type, they might suggest that messy, smelly organic teas and vegan composts are the route to go.

The key fertilizer elements:

Growing things need trace minerals, nitrogen, phosphorous, and potassium. You work these amendments into the soil before planting, and without official standards, they vary from one fertilizer brand to another.

But, you can look for the N-P-K on the label. These are chemical table symbols for Nitrogen-Phosphorous-Potassium. These appear as a three number sequence representing the element’s percentage of the weight.

Farmers committed to strictly organic products mix their own fertilizers, but even they risk undesirable chemical balances and reactions. Purely organic or homemade fertilizers release nutrients slowly, and that reduces the risk of overdoing it.

Feeding plants helps them grow. But, fertilizers make them produce. All soils have some level of N-P-K, but growth will use it up without supplementation. Cannabis fertilizers are readily available and vary from need to need. Because they pair fertilizers to the growth stage, you want to buy and use them as instructed. And, each strain has its own schedule of rooting, budding, and flowering.


Seeds and clones do not need help in their earliest stage. There’s no sense feeding them extra nutrients until they have developed a tap root.


N-P-K requirements change through the growth period. For example, seedlings look for a 2-1-2 ratio. At three to four weeks, the early plants want more nitrogen at 4-2-3. And, at five to six weeks, they need even more nitrogen at 10-5-7. You also should follow manufacturer’s instructions for growth in coco air or hydroponics.


As the plants bloom, they need a phosphorous boost. As the respective strain’s schedule approaches flowering, you can use a 7-7-7 mixture for about a week before to help the plant transition. Next, increased phosphorous enters the balance. At first flowering, the ratio is 5-10-7. Mid-flowering needs 6-15-10, and late stage flowering benefits from 4-10-7.


  • The most effective and efficient fertilizers may be handmade. Compost and meals do the job, but they remain inconvenient.
  • It makes good sense to favor product lines that offer each of the needs for your farming. Some lines offer soils, liquids, nutrients, and fertilizers, each of them balanced with its related products.
  • Provide your weed plants with a regular supply of nutrients. The amount of fertilizer given will depend on the size of the plant and its growing stage.
  • Add the nutrients or fertilizer to the water before you introduce it to your cannabis plants.
  • Do not give fertilizer every time you water your plants. Too much fertilizer will cause harm to the marijuana plants. Accumulation of fertilizer in the soil may turn the grow medium acidic.
  • Outdoor cannabis plants are expected to grow tall and bigger, the plants may need more of nitrogen. Deficiency in nitrogen will make the leaves of marijuana look dull and will eventually turn yellowish. Once these signs are detected on the plants, introduce a fertilizer rich in nitrogen.

[Updated, originally published 21.11.2017]

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