Phosphorus deficiency in marijuana plants
What is phosphorus deficiency?
Phosphorus is one of the main nutrients useful to marijuana, and other plants. It is a necessary element in all stages of plant development, so a phosphorus deficiency affects both growth and flower production.
Specifically, phosphorus is what allows the leaves to photosynthesise. Without photosynthesis there is no energy, and the plant weakens. When there is a phosphorus deficiency, the Cannabis plant is not able to develop enough roots to keep it strong and well-fed.
The flowering stage is when plants require the most phosphorus, among other elements, because this is the period when they receive the most amount of nutrients and intensity of light. Therefore, they must process it to transform it into energy and avoid burning out at the same time. Moreover, phosphorus deficiency leads to a rather poor buds production.
Phosphorus deficiency of the marijuana plant not only means weakened growth, but also high vulnerability to pests and moisture.
Generally, every marijuana fertilizer comes with a certain proportion of NPK, which are the essential macro nutrients. The medium value (P) is the corresponding value for phosphorus. You can also get phosphorus directly, and make your own preparation.
The advantage of phosphorus is that there is very little risk of overdosing and ruining the crop. On the other hand, pots love phosphorus, and consume it in surprising quantities. What does do them a lot of harm is a lack of phosphorus.
How to spot phosphorus deficiency in Cannabis plants
Many marijuana nutrient deficiencies start to become visible in the older, larger and lower leaves. It is important to notice the problem in time to balance the fertiliser before the problem spreads to the younger leaves at the top.
The first symptoms of phosphorus deficiency can easily go unnoticed by more than one grower, as it is simply slower growth and smaller leaves, then they can lead to certain weakness to diseases, from mildew to various pests.
Then the signs appear more clearly, although sometimes only partially. The leaves tend to widen and the tips bend or twist. In addition, the colour of the leaves changes to bright, bluish or bronze tones, and the colour of the stems turns red or purple.
And finally, when there is a serious deficiency of phosphorus in the plant, grey or brown spots appear all over the leaf, evidencing this deficiency. They will start to turn yellow on the surface not affected by the spots until they die and fall off.
You will also be able to detect phosphorus deficiency by the areas where these spots appear: basically, where they are exposed to light or sun, as they cannot resist it and burn. Leaves close to the buds also show this deficiency.
Before being alarmed by the presence of strange colours, keep in mind that some marijuana strains have these reddish and violet colours because of their genetics, not because of any deficiency. As for the bluish colour of the leaves, although it is also caused by low temperatures, it is good to be aware that the cold itself can hinder the plant’s absorption of phosphorus.
To avoid confusion, remember that in cases of phosphorus deficiency, none of these symptoms usually come alone. On the contrary, they usually coincide with several factors that indicate a general malaise of your marijuana. To find out for sure, it is advisable to look at the leaves that are less exposed to light: if these are healthy and green while the others are bluish or reddish, it is a bad sign.
As we mentioned above, the consequence of this deficiency is low productivity. Even if what you want are seeds, rather than flowers, you will also notice this condition.
In any case, remember that a low or high pH prevents phosphorus absorption. If you find that the pH is in the normal range, then you should proceed to adjust the phosphorus.
That’s all on the phosphorus deficiency, we have more articles on marijuana deficiencies and excesses, as well as monographs on the most important ones, such as Nitrogen and Potassium.