Cannabis Nutrients Cheat Sheet

Diagnosing Problems

The Mulder Chart shows how nutrients interact with each other in the garden. Too much of some elements cause problems with the uptake of other elements and conversely sometimes more of one increases the availability of others.

The Nutrient Deficiency Chart can help you pinpoint which nutrient is causing your issue.

The pH Chart shows you where your nutrients pH should be for maximum availability. Your ideal pH will depend on the medium you are growing in, check out the Cannabis Nutrients page for the different pH’s to use when growing in peat, coco, or hydroponically.

Download the free Monthly Garden Planner PDF for keeping track of your daily schedule.

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VPD - Vapor Pressure Deficit


Use this VPD chart to maintain the optimal temperature and humidity in the grow room.

Hydroponic Nutrients

Tip: When growing in perlite with peat or coco always use hydroponic nutrient types because the elements in those fertilizers will be in the correct form that plants can uptake immediately. Avoid all the big box store products like Miracle Grow and Expert Gardener when growing indoors with a medium like peat & perlite, these products will cause problems as they are meant for outdoor gardens where microorganisms are plentiful in the soil to help break down things like Urea Nitrogen. You can and should use microorganisms when growing indoors but you will still have issues when growing on a short 3 or 4 month schedule. Jack’s fertilizer is a popular option for a dry fertilizer that can sit on the shelf for long periods without worrying about expiring. Don’t waste your money on liquid fertilizers.

Nutrients and Additives

New growers mistakenly get it into their heads that the elements N-P-K in fertilizers are the most important and in that order. Nitrogen, Phosphorus, and Potassium are the most abundant elements in fertilizers and plants do need more of these three macro-nutrients than any other except for Calcium. In fact Calcium is critical for developing a strong vascular system in plants so creating an environment where you can maximize the Calcium uptake will also increase your plants utilization of all the other elemental nutrients. Keeping this in mind perhaps a better way to think about nutrients would be Ca-K-Mg-N-P.

Calcium is King – Calcium easily gets locked up in the soil by both Phosphates and Sulfates. This is why many fertilizers do not include it in combination with the other macro and micro nutrients. Plants use more Calcium than Phosphorus and nearly the same amount as Nitrogen so it is important to make sure it is highly available for uptake through the transpiration stream of the plant.

  • In Peat based mediums use Lime or Oyster Shell powder to both buffer the soils pH and provide a form a Calcium that is immediately available to the plant. Read more about amending peat here.
  • Use a CalMag product to supplement your primary fertilizer.
  • Plants will uptake Calcium 1000 times faster than by simple osmosis if you use an Amino Acid supplement like OminA! The Amino Acids Glycine and Glutamic Acid stimulate root cells to open up more Calcium ion channels and chelate the Calcium to prevent it from locking up.
  • High humidity levels will lead to a Calcium deficiency because it interferes with the plants uptake from the soil so keep humidity levels between 40-60%.
  • Keep plant leaves gently moving with air current to maximize transpiration.

Potassium is the health element.

  • During Vegetative growth a 1.5 to 1 K to N ratio is best. During Flowering a 2 to 1 K to N ratio is ideal.
  • Give plants a Potassium boost in mid-flowering.
  • A Potassium deficiency will show up as stalled growth, this is known as the Hidden Hunger.
  • Sulfur is responsible for aroma and flavor in flowers and fruits.
  • Too much Potassium shows up as a Magnesium deficiency.
  • Magnesium is the central atom in chlorophyll.

Phosphorus is the energy element and helps promote rooting.

  • Use a mild Phosphorus fertilizer on seedlings that have the true first set of leaves (2nd node) and on newly rooted clones (usually around day 14) to help promote root growth.
  • Use extra Phosphorus in the first 3 weeks of growth.
  • Too much Phosphorus will lock out Zinc, Iron, and Magnesium in that order.
  • Phosphorus like Calcium locks up easily in the soil. It locks up with Calcium and Iron. Mycorrhizae helps to unlock Phosphorus.
  • In the beginning of flowering plants want more Phosphorus. In middle to late flowering plants want more Potassium.

In non-hydroponic grows use a Mycorrhizae supplement that also includes beneficial bacteria to boost the plants efficiency in the root zone.

  • Make sure to feed these beneficial organisms by mixing in 1 tablespoon of Molasses per gallon of water and apply about every 10 days.
  • Real Growers Recharge is a supplemental product that includes Mycorrhizae and beneficial Bacillus bacteria and is one of our favorite Mycorrhizae products for use in the garden.

Kelp is beneficial in all stages of growth.

  • Kelp is often found as the core ingredient in both Vegetative and Bloom stimulants.
  • Use a kelp foliar spray 2 weeks before taking cuttings for clones and only use once per week, be careful because too much will burn plants.

A little fertilizer induced stress is okay. The plants are going to make antioxidants to fight the stress and that is good for improving the medicinal value of plant compounds. If the leaves are curling under and turning brown then you went too far and have hurt the plant.

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