Updated: Dec 15, 2020
As a cannabis grower, you can run into a number of problems, although, it is important to remember that these problems can be fixed once the causes are identified and a correct diagnosis is made. One of the issues that you can run into while growing cannabis is phosphorus deficiency. Although phosphorus deficiency is not very common since phosphorus is a mobile nutrient, it can cause great damage if not treated in time. But do not worry just yet; this article will not only help you identify the signs of phosphorus deficiency but will also provide you with treatments to correct the problem.
Before diagnosing your cannabis plant with phosphorus deficiency, it is important to understand the ways in which phosphorus is absorbed by the plant and how it helps your plant in vital processes.
Role of Phosphorus in Cannabis Plant Development
Phosphorus is a mobile and essential nutrient that the cannabis plant needs for various functions throughout its entire life. Phosphorus is present in the makeup of the plant; it is an important component of the plant’s DNA, RNA, and the bond between them. It is also a part of ATP’s core structure, hence, makes it possible for the plant to get energy by photosynthesizing.
A deficiency makes the plant vulnerable to many pests and also stunts the plant’s growth. These are the functions that cannabis plants need phosphorus for:
Growth and development of the plant's roots. It is also required to strengthen the stems.
It can affect the harvest since it plays a key role in flower development; it greatly impacts the density and size of the buds.
It defends the plants from diseases by keeping it healthy and boosting resistance.
Now that you know that phosphorus is crucial for proper development of the plant and also for a good harvest, let's talk about how you can determine if your plant is deficient in phosphorus.
Symptoms of Phosphorus Deficiency
When growing cannabis, you will be able to catch any problem early on by being proactive and inspecting your plant regularly. Phosphorus deficiency manifests itself as various physical and easily identifiable symptoms. These symptoms begin appearing first in older growth as phosphorus is a mobile nutrient and is transferred from older tissues to the parts of the plant where it is lacking. Here are a few signs of phosphorus deficiency:
Leaves become shiny and dark green or blue in color. The reason for the darkening of leaves is that a deficiency of phosphorus affects the utilization of carbohydrates in the plant. The carbohydrates that form as a result of photosynthesis are not adequately utilized while the plant continues to produce more. Dark green leaves are the result of carbohydrate buildup.
These leaves then get copper, bluish, or brown spots and begin to curl down. Leaves will simply become tan or brown, thicken, curl in weird shapes, and die.
Stem can become purple or reddish and the overall growth of the plant is stunted. Although, reddish or purple stems on their own is not a sign of phosphorus deficiency.
The above bullet points are the main symptoms of phosphorus deficiency. As you can see, being deficient in phosphorus can certainly prevent you from growing big and dense buds. Since it can be so devastating for the plant, it is important to act swiftly and start treatment as soon as possible.
Treatment for Phosphorus Deficiency
You are more likely to see signs of phosphorus deficiency in the flowering stage of growth because it is the phase when cannabis plants utilize more of this essential nutrient. If you notice signs of phosphorus deficiency, use the below methods to put your plant on the path to recovery.
Correct pH levels
It is highly likely that an adequate amount of phosphorus is available, but the plant cannot absorb it from the soil due to incorrect pH levels.
pH of 6.2 to 7.0 is required for absorption of phosphorus in a soil-based medium
pH of 5.5 to 6.2 is required for absorption of phosphorus in a hydro or soil-less medium
A pH level above or below the ideal range can lockout phosphorus resulting in a deficiency. If the pH of your medium is outside of the ideal range, flush your root system with fresh water. After flushing, be sure to give the plant 1/4 or 1/3 dose of nutrients according to the feeding chart that came with your nutrients. The ratio of nutrients is very important so don't deviate from the ratio shown on the chart.
Proper Watering Methods
Adapt proper watering methods to alleviate the chances of the plant becoming deficient in phosphorus. Overwatering is also a cause of this problem, hence, ensure that it is not the case for why the problem occurred in the first place.
Avoid Cold Spells
Your cannabis plant is happy at room temperature and lowering the temperature to 60°F/15°C or below can cause problems since it negatively impacts proper absorption of phosphorus.
Keep Nutrients in Check
Flushing your system with pH balanced water with phosphorus mixed in it is recommended as an excess or buildup of other nutrients, for instance, iron (Fe) or zinc (Zn), can prevent optimum absorption of phosphorus from the soil. After flushing your root zone, try some of the natural remedies. Natural sources of phosphorus include bone meal, fish meal, crab shells, worm casting, bat guano, and soft rock phosphate. Besides these remedies, you can use fertilizers, most of which contain a high quantity of phosphorus which will help fix the deficiency. If your plant is in the flowering phase, be sure to use nutrients intended for the flowering phase since those formulas have high level of phosphorus.
Once you start the treatment, you will see a gradual recovery in your plant. Do not expect the damaged leaves to recover; prune those leaves if you wish. You will see changes in the new leaves and overall growth of the plant. Give your cannabis plant some love and experience a great harvest!
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