Phosphorus deficiency in marijuana plants
Updated: 25 May 2023
Robert Bergman
12 min. read
Comments: 16
Phosphorus Deficiency In Marijuana Plants is very common.
When you buy
fertilizer from a garden center or other store, you most likely will notice its N-P-K ratio; the “P” in this ratio is phosphorus.
This alone should tell you how important phosphorus is in any marijuana plant’s healthy survival.
Cannabis plants: phosphorus deficiency
- There is an expression in Dutch:'Prevention is better than a cure'
- What causes phosphorus deficiency in marijuana plants?
- How to identify phosphorus deficiency in marijuana plants?
- How to fix a phosphorus deficiency in marijuana?
Phosphorus is an essential nutrient that comes into play mainly during your plant’s
flowering phase of life.
It assists at the beginning of your plant’s life during the
germination phase and also is useful during your plant’s reproductive phase.
Phosphorus deficiency in marijuana plants
Basically, phosphorus is extremely important for much of your plant’s life cycle. Without phosphorus, your plant will suffer.
While a phosphorus deficiency rarely occurs in plants that have been specifically planted and taken care of by a knowledgeable grower, when it does occur it can be devastating for a marijuana crop.
There are a number of factors that can cause a lack of phosphorus.
These factors can include an improper pH level,
irresponsible watering or over watering, soil that has too much moisture in it, and cold temperatures of lower than 60 degrees Fahrenheit. Temperature is especially a problem if the change is sudden.
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There is an expression in Dutch:
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Signs of a cannabis phosphorus deficiency
There are a number of ways to identify your plant as having a phosphorus deficiency.
Signs of a cannabis phosphorus deficiency
You should never add extra phosphorus to your plants unless they are clearly exhibiting some of these symptoms; otherwise, they are probably perfectly happy, with enough phosphorus to live out their happy, productive lives.
However, as soon as things start looking fishy you should start considering the possibility of a phosphorus deficiency.
You might have a phosphorus deficiency on your hands if your
plant’s growth slows down significantly and the only new leaves are very small.
The older leaves, however, will be the first to show signs of a lack of phosphorus – especially leaves located near the bottom of the plant.
The symptoms will begin there and will move upwards. The affected leaves will turn a darker green, then will show
purple and blue colors.
You also might see the edges of the leaves starting to turn tan or brown and they will start turning downward.
The leaves nearest to the base will simply turn yellow and die.
A plant with a phosphorus deficiency will also have root problems as well as other general health problems.
Petioles, as well as the plant’s stems, begin turning purple or red.
This discoloration usually begins at the base of the plant and works its way upward.
It’s important to keep in mind that some
marijuana strains are naturally tinted this color, so be aware of what is normal for your particular strain.
Not sure if your plants have a phosphorus deficiency?
If your plant experiences a phosphorus deficiency during the flowering period, its overall yield will most likely be lower than if it had sufficient amounts of nutrients.
During the flowering period, you will be able to notice if it is indeed a phosphorus deficiency simply by the part of the plant affected.
If only the parts getting hit by immediate, direct
light are affected (purple, red, or yellow leaves), while the rest of the plant remains healthy and normal in color, it is very likely a lack of phosphorus.
It is less common for plants in a low-light environment to have a phosphorus deficiency since they perform photosynthesis at a lower rate.
In contrast, plants in an intensely lit environment will be more likely to “use up” or go through the phosphorus that they have.
This is simply because phosphorus is used in the process of
photosynthesis.
This means that when photosynthesis speeds up
This usually occurs when there is a large amount of light – then the rate of using phosphorus also increases.
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How to fix a cannabis phosphorus deficiency
There are plenty of fertilizers that have an added amount of phosphorus and can be dissolved in water, such as a bloom
fertilizer.
You can also use guano which has lots of phosphorus and is easy to find.
Greensand (
wiki) and rock phosphate will also do the trick, but they release phosphorus slowly rather than all at once.
Some other sources of phosphate include bone or blood meal, worm castings or worm tea, soft rock phosphate, fish meal, and crab shell.
How to fix a cannabis phosphorus deficiency
Any budding or flowering formula is going to carry an extra amount of phosphorus, as well as most nutrient systems that are for plants like marijuana.
This is simply because these plants almost can’t get enough phosphorus, and often these plants are placed under
strong lights, which increases their rate of using up phosphorus.
Like with most deficiencies, try a product like
Marijuana Booster to restore your plant’s nutrient balance.
It will also prevent other deficiencies from becoming a problem since it contains all the necessary nutrients for your plant to thrive.
If the surrounding environment is at sub-50-degree
temperatures, your plants won’t be able to absorb phosphorus very well.
If you can’t avoid colder temperatures, try soluble phosphorus to improve your yield despite the undesirable outside cold.
If your plant exhibits signs of phosphorus deficiency when it is in its
flowering stage, it’s very important to make sure that the leaves nearest to the buds remain green. This is so they can provide as much energy as possible to the buds through the process of photosynthesis.
Since these are often the first leaves affected, you can catch the deficiency early on and prevent it from affecting any of the other leaves. If left unchecked, these buds will never reach their full-size potential.
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As soon as you suspect a phosphorus deficiency in your plant, you should check the
pH level of the soil (or water) near the roots.
If the problem was caused by the wrong pH value near your plant’s roots.
it simply means that the roots are not able to absorb phosphorus at their normal rate.
You, therefore, will need to restore the balance of the
pH level around the roots.
If your plant is being grown in a soil system, the pH level should be between 6.2 and 7.0 for it to absorb phosphorus best.
In a hydro system, keep the pH level between 5.5 and 6.2.
When you are dealing with a phosphorus deficiency caused by a pH problem, flush your whole system with fresh water that is at the desired pH level after mixing in nutrients (which include phosphorus).
This
flushing will remove nutrient salts that could be preventing your plant from absorbing phosphorus, and it will bring the pH level back to normal.
If your plant has too much
iron(Fe) or
zinc(Zn), it will prevent your plant from absorbing phosphorus normally.
There could be a buildup of nutrient salts in the soil or water (depending on your chosen system of growth).
If this is the case, then you can simply do the same flushing process that you would do if the pH level is off.
Use fresh, clean water that is at your desired pH and is infused with a balanced dose of nutrients, and flush your entire system, whether soil or
hydroponic, out with this solution.
It is important to remember that, even once a phosphorus deficiency problem is fixed, the leaves that have already been damaged will never go back to their normal healthy state.
You, therefore, should keep your eyes open for the new growth, which will tell you more about your plant’s current state of health.
You will start to see regular, healthy new leaf growth within one week of fixing a phosphorus deficiency.
It might be a good idea to
prune the damaged leaves once you see the new, healthy ones coming in.
This will allow the new leaves to get plenty of light, and will help the plant focus its energy on those leaves rather than the old, damaged ones.
Whatever you do, make sure you don’t give your plant too much phosphorus.
It generally doesn’t happen, but when it does it makes your plant get “burned”’ or the buds will be “chemical buds.”
It could also harm your plant’s absorption of other nutrients. Don’t add extra phosphorus unless you clearly identify a phosphorus deficiency.
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