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Salt in Cannabis Plants: Friend or Foe?

August 17, 2016

Salt in cannabis can be either good or bad, depending on a number of factors: the levels of other elements, whether there’s already excessive salt, the soil types, the water types and so on. Cannabis is relatively salt-tolerant, but the actual degree of tolerance varies among strains.

All water, whether recycled or not, contains various salt compounds, including sodium chloride, sodium sulfate, magnesium sulfate and calcium carbonate. Salt is comprised of ions, and a certain amount of salt ions in water is beneficial to plants. As water absorption and transpiration occurs, plants receive these helpful ions in order to strive, survive and grow.

But water that contains excessive salt can block the uptake of potassium, calcium and magnesium, which are essential nutrients for healthy plants. High levels of salt in cannabis has been shown to:

  • Inhibit-seed germination
  • Slow or stunt plant growth, since roots take on a dormant phase
  • Necrotize (burn) root hairs and tips or edges of leaves
  • Reduce chlorophyll levels
  • Cause nutrient deficiencies

In addition, high salt levels in both the water and the soil result in nutrients clashing and cancelling each other out.

Benefits of Epsom salts

Hydrated magnesium sulfate, or Epsom salts, are necessary as an additive to remove sulfates from the water in certain systems, including distilled water, reverse osmosis and ion exchange systems. Epsom salts are usually applied to plants that are visibly lacking in magnesium, or for strains that are typically magnesium-deficient.

Magnesium sulfate has many positive effects on cannabis:

  • It helps plants to more readily take in potassium, phosphorus and sulfur from the soil, enhancing the uptake and effects of nutrients and minerals.
  • It facilitates the creation of chlorophyll, which is critical for photosynthesis.
  • It helps maintain the plant’s structure and health.
  • It plays a crucial role in both seed production and germination.
  • It is especially important for long-life plants, such as mothers or outdoor strains with a slow finish.
  • It is easily “ingested” by plants and doesn’t build up in soil over time.

Signs of magnesium sulfate deficiency in cannabis plants include slow plant growth, yellowing leaves (starting at the bottom of the plant), and leaves that have a slight curl to them. To revive mothers or root-bound plants due to salt buildup and being in the same pot for too long, a gentle Epsom salt solution will help to dissolve accumulated salt by cleaning out root cells.


By Mary Kaye Eisele
Image Credit: By kevindooley [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
Cannabis Cultivation Today articles are for informational purposes only and should not be considered legal guidance or advice on grow practices. You should contact an attorney or a qualified cultivation consultant for specific compliance and cultivation advice.

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