Cannabis Nutrients part seven: Sulfur and Cannabis

What’s going on everyone, I hope everything went as planned.  Today post is going to talk about a few of the ways that cannabis uses sulfur (S) and some of signs to look for during a deficiency.  It is one of three secondary nutrients that a cannabis plant needs to thrive.  This element is so abundant in rainwater, the soil and some tap water, that a deficiency is rare to see in plants grown outdoors in the ground.

The cannabis plant uses a process called transpiration to absorb water and nutrients through the roots and carry it  throughout the plant until it’s released as vapor through the pores on the leaves.  This process can’t happen without sulfur because it is used to build a strong, healthy root system.  Chlorophyll as well as amino acids, plant proteins and enzyme also can’t be made without it either.  It’s also involved in seed production.  The cannabis plant will use larger amounts of sulfur during vegetative growth to help build the framework that going to support the plant during flowering.

Symptoms of Deficiency

Sulfur is known as an immobile element, which means once it’s absorbed by the plant it gets locked in place and isn’t able to be moved within the plant. So when a deficiency does happen, the symptoms will first be seen on the upper, newer leaves.  The most obvious symptom will be chlorosis (leaves turn pale green, yellow, or white between the veins) that will start at the back of the leaf and move its way forward.  The underside of the leaves will sometimes turn an orange or pinkish red color.  The leaves will look smaller because growth will also slow down during an (S) deficiency as well.  If left untreated the leaf will turn gold, brown, rust or gray in color and feel rough, dry and die.  In the flowering stage the deficiency can make the to buds die since that will be the upper, newer growth.  Inexperienced growers will sometimes confused a sulfur deficiency with a (N) deficiency.  The most obvious difference is that the chlorosis will start in the lower, older leaves during a (N) deficiency.

Causes and Cures

  • Cannabis absorbs sulfur best at a pH range 6.0 and higher. Keep in mind that all of the primary and secondary nutrients are easily absorbed when the water/nutrient solution has a pH of 5.5 to 6.5.  Anything higher or lower than this will make the marijuana plant struggle to take up some nutrients and could easily cause a nutrient deficiency along with other problems.  It doesn’t have to be exactly the same every time, that’s why it’s called a range.
  • Too much nitrogen will make a cannabis plant lockout sulfur and cause a deficiency. Nutrient lockout happens when there are high levels of one kind of nutrient in the soil that blocks other nutrients from being absorbed.  One remedy for lockout is to flush the plant to break up the nutrient buildup that is on the roots and in the soil.
  • Low temperatures and a constantly wet soil/grow medium will cause the plant to absorb sulfur slower also. Making sure your soil is dry before watering again, so adjust your watering schedule to help with this.
  • Epson salt is also good source of sulfur and can be mixed into water at about one teaspoon per gallon of water.Note:  Leaves that showed signs of chlorosis could recover after the deficiency is brought under control. When leaves get necrotic or dead they will turn gold, rust, brown, or grey in color and crumble when they’re handled. This is dead plant tissue that won’t recover.


Sulfur toxicity is rare because cannabis uses so much it during its lifecycle, but when it does happen, the first sign is usually slowed growth.  We have to remember that too much sulfur will also lock out nitrogen and cause a deficiency.

Well that’s all I have to tell you about sulfur, I hope it helped.

Don’t forget to check out the podcast “In My Grow Show” (Click here to link and listen)

Grow, Learn, Teach.

Click here for pH up down kit

Click here for Epson salt


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