How To Spot Phosphorus Deficiency In Your Cannabis Plants

Phosphorus is one of the critical nutrients used by cannabis plants to grow from delicate seedlings into healthy, mature plants that produce robust, THC filled buds. Without enough phosphorus, your cannabis harvest will fall short, and you might find that your plants never reach full maturity or the flowering stage. In this guide, we’ll cover everything you need to know about detecting and treating phosphorus deficiency for happy, healthy cannabis plants. 

What Is Phosphorus?

Phosphorus is a chemical element used by plants to assist in photosynthesis, nutrient absorption, growth phase transitions, and more, and is considered ‘second’ to nitrogen as the most vital nutrient for healthy plant growth. As it pertains to plant life, phosphorus refers to phosphates’ salts that help promote nutrient uptake and energy production. 

Benefits of Phosphorus for Cannabis Plants

In cannabis Sativa plants, phosphorus helps support three vital processes that help the plants reach their different growth phases. They include photosynthesis, the storing and production of energy, and the uptake of nutrients. In addition to assisting with the growth and nutrition of individual plants, phosphorus also maintains genetic integrity, which ensures genetic lines are consistent from one generation to the next. 

Signs of Cannabis Phosphorus Deficiency

It is essential to learn what signs to look for – before it’s too late – to avoid your cannabis plants being negatively affected by phosphorus deficiency. Cannabis plants will display several visual indicators of a phosphorus deficiency. Thus, If you know what to look for, you will easily catch the problem early. 

Red Stems

In some cases, a phosphorus deficiency may produce red stems. If you notice stems (notably lower stems) turning deep red, this could be a sign that your plants are craving some phosphorus. Note: red stems will not always accompany phosphorus deficiency, so do not rely on this as a valid phosphorus deficiency indicator. 

Dark Lower Leaves

Cannabis plants should have pleasant medium to light green leaves with little to no shine. Still, when your plants experience phosphorus deficiency, the lower leaves may turn dark green/blue and appear slightly shiny. 

Leaf Discoloration

One of the most common signs of a phosphorus deficiency is leaf discoloration. The delicate green leaves of your cannabis plants may produce brown or yellow spots, which could also be an indication of a pH imbalance as well as a phosphorus deficiency.

FAQs of Phosphorus Deficiency

Want to know more about phosphorus deficiency in cannabis plants? Here are just a few of the most frequently asked questions: 

What Causes Phosphorus Deficiency? 

Many factors can impact phosphorus and nutrient balance. The most common reason cannabis plants become phosphorus-deficient is that breeders do not feed them adequate nutrients. Cannabis plants require a specific blend of nutrients during different phases of growth, including phosphorus, to assist with nutrient uptake, photosynthesis, etc. Without added nutrients, cannabis plants can drain the soil of its phosphorus supply. Cold weather, low soil quality, harsh chemicals and herbicides, and invasive insect species may also trigger phosphorus deficiency. 

How Can Phosphorus Deficiency Be Fixed? 

Phosphorus deficiency can cause severe problems for your cannabis crops. Yet, if you catch the problem early, it isn’t too difficult to fix. Here are just a few solutions to phosphorus deficiency: 

  • Water your plants with cannabis-approved nutrient blends that include phosphorus
  • Don’t over or under-water
  • Keep your plants warm – grown inside if possible
  • Correct pH levels – your soil should be around 6.0 – 6.5 pH

What Are the Consequences of Untreated Phosphorus Deficiency?

It isn’t the end of the world for a cannabis plant to experience mild, brief phosphorus deficiency. However, long-term phosphorus deficiency can cause serious damage to the health of a cannabis plant. If left untreated, phosphorus deficiency can reduce the cannabis plant’s ability to absorb nutrients, ward off disease, and advance from the vegetative to the flowering stage. Bottom line: if you detect a phosphorus deficiency, don’t hesitate to take action immediately.