Nutrient deficiencies in marijuana plants are not just an annoyance for cannabis growers; they can also kill your plants. If you want to grow the best marijuana possible, you need to learn how to recognize and resolve nutrient deficiencies. Some of my favorite solutions for nutrient deficiencies are easy to do. You simply need to know when to use them.
Cannabis nutrient deficiencies
- Do your plants have a nutrient deficiency?
- Nutrients and pH
- Identifying the lack of nutrients
- The big three: macronutrients
- Other nutrients
- Getting your plants back to health
- FAQs about marijuana deficiencies
Do your plants have a nutrient deficiency?
Deficiencies are not the only possible problems your plants could have with nutrients. They could also have too much of something, including the three essential nutrients (Nitrogen, Phosphorus, and Potassium, or N-P-K). So how can you identify it?
First, reflect on whether what you have been feeding your plant has been entirely balanced, specifically with regards to N-P-K. After that, test the pH value of the soil and water that you’ve already been giving them. The nutrients deficiencies can be caused by many things, but the most significant factor is pH value. If the pH levels aren’t perfect, fix them. If they are balanced and your plants still look unhealthy, the issue may be connected to sunlight. This is an easy fix.
Before you get too confused or overwhelmed by the possibilities, make sure you understand the problem. If your plants are receiving plenty of sunlight and a balanced amount of water, the chances are good that the problem lies with the nutrients.
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Nutrient deficiencies or disorders in marijuana plants can occur with every growing technique and in every growing medium. It doesn’t matter if you use rock wool, soilless, aeroponic and hydroponic or soil.
In fact, within the world of cannabis cultivation, nutrients issues are a constant concern. Although the macronutrients (potassium (K), phosphorus (P), and nitrogen (N)) are the usual offenders there are others to consider. You can also end up with calcium, zinc, magnesium, or other imbalances, although these are slightly less common.
Indoor marijuana growers usually have more problems with nutrient disorders than outdoor marijuana growers. This is problematic because a nutrient deficiency always slows the growth of the cannabis plants down.
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Nutrient disorders sicken the marijuana plant, and a disproportionate amount of nutrients can cause toxicity or nutrient burn. It can also cause the lock-out of other vital minerals. You’ll want to learn how to prevent nutrient deficiencies so that you can increase your chances of success.
Nutrients and pH
How do you know if your plants are deficient? Well, if your plants seem unhealthy, there is a good chance they could have a nutrient deficiency. Usually, you can notice a nutrient deficiency by symptoms in the pH of the water and soil around the plant. A balanced pH can ensure your plants absorb all of the nutrients they need.
The pH scale is how growers measure the acidity or alkalinity of the soil and water around their plant. The scale ranges from 1 to 14, with 7 being neutral pH. 1 is the most acidic while 14 is the most basic (alkaline). When you are watering your plants, you want to be entirely sure that the pH levels are appropriate; otherwise, the plants can be damaged, and their health can deteriorate.
Adjusting the pH is simple. You are simply making the environment (whether soil or water) more alkaline or acidic, depending on its current level. The pH for cannabis should be somewhere near the neutral middle of the pH scale, somewhere around 6 or 7. Although hydroponics systems can sometimes support a cannabis plant with a pH of as low as 5.5, the ideal range is somewhere around 6. Every time you add or remove a nutrient, it affects your plant’s pH and general ability to absorb nutrients. Understanding this relationship will help you grow the healthiest plants.
Testing the pH level is always important, but it is especially so when you need your plants to quickly absorb one or more nutrients. Testing pH levels is also extremely easy. You only need testing strips or a ph meter from a local gardening supply shop. This will help you avoid over or underfeeding your plants. You should also be able to purchase commercial mixes of soil that easily let you modify and stabilize the pH of your own soil. PH strips and meters are also online available at this link.
The closer your pH level is to 7, the faster your plant will absorb nutrients of any kind. With any plant, the best way to feed your plants specific nutrients is through “foliar feeding.” This means making a tea and spraying your plants’ leaves with it. Just be sure to avoid doing this during the middle of the afternoon, when the temperature is at its highest. It is better to do it early in the morning or right when the sun has gone down.
Identifying the lack of nutrients
The most likely explanation for an unhealthy plant is a lack of nutrients in the soil. It can also be due to the roots’ inability to absorb nutrients. That is why it is important to know how to identify which nutrients are posing the issue. In fact, most experienced growers will tell you that the challenge with nutrient deficiencies is not actually providing soil amendments. The challenge is identifying which nutrients are causing the trouble.
You can look at your plant’s symptoms, but just looking can be tricky because many nutrient deficiencies appear the same to the untrained eye. If, after reading this article, you are still unable to identify which nutrient your plant is lacking, try flushing the soil with water. This step will remove any excess nutrients. It also removes the variable of there being a deficiency due to one nutrient being out of balance. Too much potassium, for example, could prevent your plant from taking in iron.
- Flush the soil
- Test the pH level
- Add whatever you think you need
- Check the pH level one more time.
Want to find out which nutrients your plants are missing? Continue reading to learn what each nutrient does, why it is important, and how to fix a deficiency.
The big three: macronutrients
Three types of deficiencies are incredibly common when growing marijuana. These aren’t the only problems your plant might face, however they are a good place to start looking. The big three are what’s called macronutrients. As long as your plants have these three foundational nutrients (nitrogen, phosphorus, and potassium), they will be healthy enough to achieve a decent harvest.
As with most marijuana growing problems, early detection is essential. If you identify problems early, you can make adjustments that keep your plants healthy and guarantee a successful harvest. Here’s how each nutrient functions in the marijuana plant, and how to identify a potential problem.
Nitrogen is one of the most essential nutrients for healthy plant growth, and because it’s so heavily used by cannabis, it’s not uncommon for plants to develop nitrogen deficiencies.
Nitrogen is used for a wide variety of plant processes, from photosynthesis to the production of vital amino acids and chlorophyll. Chlorophyll is essential to the process of photosynthesis while amino acids are what make up proteins so you can understand why this nutrient is vital for a healthy plant.
Symptoms of deficiency
If your plant is experiencing a lack of nitrogen, its symptoms will be mostly seen in older leaves, starting between the base and middle of the plant. In general, the signs of a nitrogen deficiency are yellowing leaves. If the lack is left unchecked, the yellowing leaves can wither and die.
Your nitrogen-deficient cannabis plants will look perfectly green at the top but yellowing more as you look down towards the bottom. Although nitrogen deficiencies will usually begin in the bottom leaves of the plant, they will eventually spread up to the top. Your plant is at the greatest risk for a nitrogen deficiency when it is in its flowering phase. This is because cannabis plants store nutrients in their leaves. The flowering phase will require this stored cache, thus using up all that it has.
Your concern should grow if the plant is in its vegetation phase. This is simply because the plant needs healthy, green leaves to catch the sun’s energy. They need the sun to produce as much energy as possible and grow. If the leaves are yellow, they won’t help in this process.
Some growers describe seeing symptoms such as the leaves curling over like a claw, with the leaf stems going very brittle. The leaves may also turn a very dark shade of green. If it’s during the flowering phase, the flowering will likely have slowed down as well. In this case, it is probably a pH issue that is leading to nitrogen toxicity. That means that your plant actually has too much nitrogen, but not because you are feeding it too much; instead, it is due to a pH imbalance.
How to Treat It
You will need to find a way to quickly increase the amount of nitrogen that your plant is absorbing. Blood meal is one easy way of doing this, as are dried blood, cottonseed meal, and bat guano (also known as bat manure). There’s also fish meal (also known as fish emulsion) and worm castings (worm “manure”). You can pick any of these up at your local gardening store, or purchase them online.
Always make sure you’re using a fertilizer with the right ratio of macronutrients. These vital nutrients are nitrogen, phosphorus, and potassium. Plants require extra nitrogen during the vegetative stage of growth, so make sure they are getting enough! If you need a quick nitrogen boost and don’t have time to worry about long-term fixes, you can use bat guano or compost.
Although the yellow leaves won’t ever return to their green state and will instead simply fall off the plant, this doesn’t mean that your plant won’t recover. If treated correctly and promptly, your plant should recover within a week, and new green leaves will replace the lost yellow ones. Before and after you add the soil amendments, be sure you are testing the pH level, as it could increase or decrease when you are treating the nutrient deficiency.
While not as common as nitrogen deficiencies, phosphorus deficiencies are a definite possibility, especially in hydroponics systems. Phosphorus is primarily responsible for helping your plant grow roots, as well as increasing the strength of its leaves and stems. It also aids in seedling germination, making it an especially essential nutrient during your plant’s flowering phase.
In fact, many would say that phosphorus is actually most important during the flowering phase of growth. If your plant lacks phosphorus during the flowering phase, you will limit the potential yield. Don’t be dainty when providing your plant with phosphorus; it is usually necessary in hefty quantities.
Symptoms of deficiency
If your plant is not taking in enough phosphorus, its growth will slow down, and it will generally appear frailer and lacking life. The initial symptoms of a phosphorus deficiency are darkening foliage and slowing growth. The leaves’ edges on your cannabis plant will lose their vibrant green color – they may even turn brown – and will start to curl in. Other plant parts like petioles will also darken, possibly becoming more blue or red., but it also adds structural strength to the roots and stems of the plant.
These symptoms are more likely to appear during the coldest days of the growing season since this is the time when marijuana plants often have the most difficult time absorbing phosphorus from the soil. In addition to the cold, if the soil is too wet or too alkaline, the same problems will occur.
How to treat it
You may need more phosphorus during colder temperatures. Try buying fertilizers and plant foods with a higher ratio of phosphorus. As long as the N-P-K ratio exceeds 5, the substance will be helpful for your plant’s phosphorus deficiency. Fertilizers developed explicitly for the flowering phase work well, as does bat guano. Water-soluble fertilizers will be your best option for maximum efficiency and ease of use.
Certain all-purpose plant foods (Miracle-gro, for example) work just as well, however, you should only use half of how much is recommended. An overdose could be lethal for your plants.
Bone meal, worm castings, and bat guano also provide quite a bit of phosphorus. A harder-to-find solution would be crab shell or crab meal. Results should be evident within a week.
Potassium deficiencies are relatively common in the world of marijuana growing. This is because, with most fertilizers, potassium occurs in the lowest ratios. Compared to the other macronutrients, less potassium is required by the plant.
However, just like the other two nutrients of the primary three, potassium is vital for your plant to function properly. Potassium is primarily responsible for your plant’s water respiration and resistance of most diseases. Not only that, but it also is helpful in the photosynthesis production and conversion processes. Finally, potassium assists in the water circulation, helping to move water through the entirety of your plant, making it especially important for the flowering and vegetative phases.
Symptoms of deficiency
A potassium deficiency has unusual symptoms: the plant might grow taller more quickly and look healthy at first but keep an eye on the lower foliage. If the plant doesn’t have enough potassium, the leaves can turn brown and begin to die. Ultimately, this will slow your marijuana plants’ growth and development.
Indeed, plants that are lacking in potassium will have very slow-growing leaves that might look like they are burnt on their tips and edges. Marijuana plants that are not as rigid or are easily bent or broken (by you or by the wind) might also be lacking potassium. For existing mature leaves, they might appear mottled and yellow in some specific areas (between the veins at first, then the entire leaf). These leaves may also become wholly yellow and die. One of the most harmful effects of a potassium deficiency is that your flowering phase would be delayed, leading to a disappointing yield.
You also might notice areas where growth slows or becomes irregular. Remember that potassium is very important to the transfer of water and other nutrients throughout the plant. This means that if you have a substantial deficiency, it can affect the health of the whole plant.
Different symptoms will occur if your plant has potassium toxicity; the edges will begin to yellow, then the tips will brown, and finally, there may be some spotting, very yellow edges, and curling over of the leaves.
How to treat it
Because marijuana plants easily and quickly absorb potassium, this particular deficiency should be easily fixed. Even if the pH level isn’t perfect, it still should be able to absorb the nutrient quickly and efficiently. One way to combat a lack of potassium is by adding a fertilizer that has potassium to your store-bought fertilizer (if you are already using it). You can try adjusting the fertilizer mix you are using or add a water-soluble potassium additive as well. If you would prefer an organic method, you can also use wood ashes, kelp meal, granite dust, or sulfate of potash. You should see results within a week.
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Although the big three macronutrients are the easiest to identify and are the most common deficiencies, advanced growers, in particular, are going to want to know about the rarer deficiencies that could affect their marijuana plants. There are tons of nutrients to consider altogether, so keep reading for some helpful tips.
Magnesium encourages strong, healthy veins and stimulus on the creation of marijuana leaves. It also plays a role in producing chlorophyll and breaking down enzymes.
Magnesium deficiencies are relatively rare for outdoor cannabis growers, but it’s found indoors and with hydroponics systems. Usually, it will affect the lowest leaves of the plant at the beginning, causing them to yellow and weaken. Although it rarely occurs when growing outdoors, a magnesium deficiency can happen in any plant medium and hydroponic system.
Deal with a Magnesium deficiency quickly or else it will become a major problem. Magnesium can move around easily, so the plant can move it from the old leaves to new ones. This explains why magnesium deficiency has a tendency to show up towards the bottom of the plant and on the older leaves. Left unchecked, the leaves will die.
This deficiency can also work its way up the plant from bottom to top until it reaches the crown. Magnesium is a crucial element for the development of chlorophyll in the cannabis plant, so don’t let the problem worsen, especially in the early stages of growth.
The easiest and most common way to fix a magnesium deficiency is the application of Epsom salts. Be careful, though, you want to make sure you’ve diagnosed the deficiency correctly before trying to fix it. If you apply too many unneeded nutrients, you could be causing a whole new problem instead of fixing the real issue.
Signs of a magnesium deficiency
Symptoms begin in the lower leaves when they start to turn yellow and show chlorosis. The leaves start turning inward and will soon die. The outlining of the leaves will feel dry and brittle. The deficiency will move up to the middle and upper half of the leaf, and the growing shoots will start going from pale green to white. All of the petioles and stems will also become purple in color.
Sometimes you may notice light brown spotting on the edges if the issue continues to worsen, even though it is possible this could be a little bit of another deficiency that comes along with magnesium deficiency.
One surprising symptom that some growers notice is the development of red stems on their marijuana plants. If you see your plants starting to have stems that are red in color, you can be sure that it is due to a magnesium deficiency. Try to fix the problem with something such as Epsom salts (see below), but even more importantly, test the pH levels of the soil and the runoff. No amount of Epsom salts will help unless the pH levels are balanced.
You can easily avoid and solve magnesium deficiencies once you are aware of how to handle it. We will go into more detail about this below.
How to fix a magnesium deficiency
There are several ways to resolve magnesium deficiency, but one of the better options is a product called Bergman’s Plant Booster. This is one is very popular because it enhances the quality of your yields and provides a good balance of nutrients.
More options are:
- Dolomite lime
- Magnesium sulfate
- Garden lime
- Worm castings
- Epsom salts
Since both Epsom salt and Magnesium sulfate (wiki) are water soluble, they work the best. For hydroponics systems, Epsom salts are by far the simplest solution. For every gallon of water in your tank add a teaspoon of Epsom salts. Give it a quarter of the initial dosage for every consecutive treatment. If you like, you can even add Calcium-Magnesium (available at this link for only $20)
Magnesium and pH levels
If the pH of your plant’s roots drops too low, the marijuana plant could display signs of magnesium deficiency, even more so in hydro (check these hydro ph levels). This occurs as a result of the pH of the roots not being at the right ratio, which causes the plant to fail to receive magnesium properly from the roots.
Usually, with this deficiency, the magnesium is there, but the roots are not able to receive the magnesium efficiently because of the wrong pH. This is why it is necessary to keep the right pH. It is the easiest way to prevent magnesium deficiency.
Providing additional magnesium to a system that has a pH lock-out will most likely not help. The plant can’t take in any magnesium until the pH is corrected. If your plant has plenty of magnesium, giving it more could cause other deficiencies by shutting out other nutrients the plant needs.
If you’re growing marijuana in soil, magnesium is better received by the roots in the 6.0 – 7.0 pH rate. If you’re growing marijuana in hydro, magnesium is better absorbed when the roots have a pH of 6.0 – 6.5.
If suspicion sets in and you begin thinking you plant has a magnesium deficiency, flush the system with pure, pH’d water that has a normal dose of marijuana-friendly nutrients in it (including magnesium). This will remove all nutrient salts that may have damaged the plant’s ability to absorb magnesium and help replenish the pH to the right ratio.
Read the article How to rinse a hydro system for more information about flushing.
One of the rarer deficiencies is boron. It’s not common for cannabis cultivation, but it can certainly damage the plant’s potential growth. The most visible signs of boron deficiency happen on growing leaf tips. These areas may begin to turn brown or gray.
Eventually, if there isn’t enough Boron, your plant’s growth will slow significantly or it will just stop. In addition to the damage to those tips, the leaves may also start to develop dead spots. They will be small and scattered and might go easily unnoticed.
Make sure you take counteractive measures to fix boron deficiencies right away. Fixing the problem usually starts with adjusting irrigation processes and making sure you’re getting the boron back into the environment. Boric acid is a simple and common choice for growers, but compost and natural mixes are also potential options to bring the levels back to normal. Read more about boron deficiencies in marijuana plants.
Calcium deficiencies are relatively uncommon for outdoor growers but are not uncommon when growing indoors or in hydroponics systems. Much of this is due to the water. Some areas have water supplies without sufficient amounts of calcium. In those situations, if growers don’t add calcium to their irrigation reservoirs, there likely won’t be enough for the plants to thrive.
Additionally, if you’re growing in a hydroponics system and you’re only using water and nutrients in a solution, then you might be missing a good source of calcium. Calcium deficiencies will usually display symptoms of big dead patches on unusually dark leaves.
The symptoms of calcium deficiencies usually begin in older growth. Branches may weaken, and any additional weight or stress could cause them to crack or break off. If you don’t address a calcium deficiency early, the plant may also develop issues in the root systems. Thankfully, treating calcium deficiency is usually a pretty simple process. Growers often use lime, applying it to the soil or substrate and letting the plant take it from there. Read more about calcium deficiencies in marijuana plants.
Copper deficiencies in cannabis plants are relatively uncommon, but they can cause a lot of damage to new growth. Initial symptoms typically include necrosis of the plant matter in young leaves. Necrosis causes the leaves to look brownish or blue-gray at the tips. These new leaves, flowers, and other new growth can become limp and weak if there isn’t enough copper.
Copper is essential for marijuana plants. Thankfully, it easy to add to a plant’s environment. You need to make sure you do your part. Many fungicides contain copper, but there are other options, too. We’ll cover more of your copper options farther along. Read more about copper deficiencies in marijuana plants.
Iron deficiencies are not uncommon for cannabis plants. The first sign of an iron deficiency is in the new growth of the plant, especially the leaves. The upper leaves will usually be the most affected, becoming discolored and yellowing distinctively.
With an iron deficiency, the veins of the leaf will remain green. However, the leaf itself won’t have enough chlorophyll. Iron holds a vital role in the production of chlorophyll in cannabis plants.
Beware: an iron deficiency and a magnesium deficiency can look very similar. What’s the main difference? An iron deficiency will primarily affect new growth on the plant. That means the top leaves will be affected far more than those at the bottom and middle of the plant.
In general, iron deficiencies often occur alongside improper pH levels, so keep that in mind. This type of deficiency also often partners with manganese and zinc deficiencies. Think your plant is low on iron? Read how to treat iron deficiencies in marijuana plants.
Manganese deficiencies are also relatively uncommon in cannabis cultivation. These deficiencies tend to happen in tandem with zinc and iron deficiencies. If you notice this deficiency, remember to carefully test and analyze your plant’s environment so that you don’t miss others.
This type of deficiency will display symptoms in new growth, primarily in the leaves. The leaves will develop dead spots and begin to yellow. On the other hand, too much manganese can inhibit nutrient absorption and cause iron deficiencies.
Manganese is vital for the creation of chlorophyll and the production of nitrates. Make sure you have plenty of manganese in your nutrient solution or plant substrate. Purchasing this nutrient in a water-soluble form is always a good idea since it simplifies the application process. Many growers also prefer compost or greensand. Read more about manganese deficiencies in marijuana plants.
Molybdenum deficiencies are very uncommon. If they do occur, they will cause unpredictable, and likely, negative effects on your cannabis plant. Without enough of this nutrient, the plant’s middle leaves will begin to yellow. Also, any new foliage will grow out warped or stop growing entirely.
The shoots will begin to curl, and the leaves can develop a strange crimson hue at the tips. Molybdenum aids primarily in the development and production of ammonia for the plant.
One of the main reasons why molybdenum deficiencies are so uncommon in cannabis plants is the tiny amount required. Plants don’t need very much of it. That also means you should show restraint when treating this type of deficiency. Growers often favor sprays and infused solutions to treat the plant. Read more about molybdenum deficiencies in marijuana plants.
Silicon deficiencies almost never occur when growing outdoors, but they are possible in controlled indoor environments. This nutrient is highly abundant in nature. It’s also well represented in fertilizers and nutrient solutions.
Silicon is necessary for plant production in general. A deficiency weakens the branches and stems and inhibits the photosynthesis process. This nutrient also deters insects and pests. That’s why you might notice an increase in insects if your plant is deficient.
To treat a silicon deficiency, growers have a number of different options. Many growers favor diatomaceous earth or liquid silicon. Just remember that silicon deficiencies are rare, and it’s always a good idea to check other causes before trying to add more silicon. Read more about silicon deficiencies in marijuana plants.
Sulfur deficiencies don’t occur too often since most fertilizers include enough of this nutrient. Symptoms of a deficiency include yellowing of new and developing foliage, as well as stunted growth.
The new leaves may also be narrower and more brittle than they should be. Sulfur plays an essential role in a number of different vital processes, including chlorophyll development and root system growth.
Checkout or full guide on how to stop sulfur deficiency in marijuana plants!
If your plants develop sulfur deficiencies, treat them with an application of potassium sulfate or Epsom salts. Read more about sulfur deficiencies in marijuana plants.
Despite the moderately small amount of zinc required in the cannabis plant, zinc deficiencies occur fairly regularly. Symptoms of a zinc deficiency include twisted foliage growth and yellowing of the veins of the older leaves.
It’s also possible for the plant to begin to lose color and grow paler. During the flowering phase, you may notice the same issue in the buds. They may even curl or become deformed. Zinc deficiencies often occur in tandem with iron or manganese deficiencies.
Zinc plays an essential role in many different plant processes, including plant development and the production of vital enzymes. Severe deficiencies can cause the plant to wilt or even break the stem. Because of the linkage between zinc, manganese, and iron, it’s important to exercise caution when treating a zinc deficiency. Read more about zinc deficiencies in marijuana plants.
Getting your plants back to health
If you properly resolve a deficiency issue, the yellowing and discoloration of the leaves should cease almost instantly. Damaged leaves can bounce back to a certain extent. What matters most is that you ensure the issue is not still spreading to the other leaves on the plant.
Don’t remove any discolored leaves until you are confident the issue is resolved. The goal is not to spread the condition to the newer leaves. It is better if any continued discoloration occurs on the leaves that were already damaged.
Once the issue is resolved, then you can remove the damaged leaves. They should be almost completely discolored. Prune lightly so that you do not stress the plant any further. If your leaves aren’t discolored, make sure to leave your fan leaves intact. They are absolutely crucial to the health of your plants.
Remember, pay close attention to the growth of your plant. If you suspect any issues, use the list of symptoms to determine if there is a deficiency. No matter what type of deficiency your plants had, the new growth will really show you whether they are improving or not. Once you have restored balance, it may take a few days before the deficiency is completely cleared up.
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21 Tips for solving cannabis nutrient deficiencies
There are a variety of things that could go wrong with your cannabis plants. A nitrogen deficiency leads to fewer buds, while calcium and magnesium are more common indoors. Here are 21 ways to address them.
Nitrogen is the most common nutrient deficiency in marijuana and causes severe yellowing on the leaves. If left untreated, it will cause leaves to decay and fall off. The stress also causes plants to enter their flowering stage early with fewer bud sites. The overall result being fewer yields.
Alfalfa and cottonseed meal
To correct nitrogen deficiencies in your marijuana garden, adding granulated products made from alfalfa and/or cottonseed to the soil provides protein which counteracts the deficiency.
Pressed alfalfa hay and the remaining solids after cotton seeds have been pressed for oil act as slow-release nitrogen fertilizers when combined with the soil. Alfalfa meal or pellets are used as animal feed and is also used as a fertilizer to increase organic matter in the soil.
Alfalfa contains trianconatol, which is a fatty acid stimulating growth. Cottonseed meal is high in nitrogen. However, due to the use of pesticides in cotton fields, it is imperative you use pesticide-free products on your cannabis.
Fish emulsion and fish meal
Fish meal, which is the ground up inedible parts of fish into a powdery substance, and fish emulsion, which is the liquid remnant of fish after having been pressed for oil are effective additives available to the marijuana gardener as a correcting measure for nitrogen deficiency. The bonus with fish-based treatments is the additional micronutrients they contain which aids in preventing additional nutritional inadequacies.
Both amenities are soil enhancements. Fish emulsion releases nitrogen to your cannabis quickly, while fish meal provides a slower, steady release. Consult your local garden center (discreetly) to see which option better serves your needs, based on symptoms.
Guano is an effective fertilizer consisting of the feces and urine of seabirds or cave-dwelling bats. It is high in nitrogen, phosphorus and earth salts. Bird guano has a higher fertilizer value than bat guano. Be sure to read labels for the concentration of nutrients you need to correct a particular deficiency.
Guano has a much less pungent odor than animal manure, which makes it an attractive additive in correcting nutritional deficiencies in the soil. It can also be used as a compost activator.
Guano can be applied as a foliar spray or soil drench by mixing one quarter cup guano per one gallon of water. Liquefying the manure allows the nutrients to be more readily absorbed by your marijuana plants. The product is available at garden centers or online.
Urea, made from urine, as the name suggests is high in nitrogen and may be used to correct nitrogen deficiencies. However, once urea mixes with the soil, it undergoes an intensive chemical change releasing ammonia into the soil.
This can burn seeds and seedlings. Follow label directions and do not apply in extreme heat.
Calcium & magnesium deficiencies
Calcium deficiency leads to severe root decay and even root death if left untreated, while magnesium deficiency causes your plants to become sickly and droopy. Both types of plant deficiencies result in severe discoloration in the form of rust and brown spots on your cannabis plant.
This is another option for correcting calcium deficiency. It can be found at larger garden centers as a fertilizer or through scientific supply houses. Calcium nitrate contains fifteen percent nitrogen and can raise the soil pH level if needed. Again, use caution using any calcium correcting control during the flowering stage of your marijuana plant, so as to avoid providing more nitrogen than is needed.
Gypsum is hydrated calcium sulfate, a naturally occurring mineral in most of the United States. It is used in agriculture to correct the sodium levels in soil. Gypsum, when added to the soil, is a ready-made source of calcium and sulfur and reduces the aluminum toxicity, along with ammonia which may be present due to the application of certain fertilizers.
Additionally, if your cannabis grow site has experienced soil crusting, adding gypsum to the surface will break it up, allowing the emergence of tender seedlings. If your crop is in an area with clay soil, applying gypsum before planting has been known to prevent crusting.
Otherwise known as Epsom salts, magnesium sulfate can quickly correct magnesium and sulfur deficits. In hydroponic gardens, add a solution of one teaspoon Epsom salts per gallon of water to the reservoir or use as a foliar spray. This recipe can be applied to outdoor cannabis gardens, as well.
Epsom salt granules can also be mixed in with the soil when preparing the garden for planting. Magnesium is critical for seed germination and the production of chlorophyll in marijuana plants. It strengthens cell walls, which is one reason the use of Epsom salts (discovered in Epsom, England) is such a popular fertilizer for the organic gardener.
The following fixes are techniques used when there’s more than one type of nutrient deficiency in your marijuana garden. Try these tips for treating multiple problems at once.
Cal-Mag (calcium – magnesium)
As the name suggests, Cal-Mag contains calcium and magnesium, along with nitrogen, phosphorus and potassium, so be careful when considering this control method. Do not use Cal-Mag during the flowering stage or the flowers will receive too much nitrogen.
This treatment should be applied during the vegetative stage. Cannabis roots absorb calcium and magnesium in a proper pH level (6.5). If the pH is off, calcium deficiency can result in the forming of dead spots in the leaves, then crinkling or spotting. Follow instructions and don’t over-apply or you can end up raising the essential nutrient levels too high.
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Inorganic nitrate salts are water soluble, which allows for quicker penetration. Nitrates used in agricultural fertilizers are ammonium, sodium, potassium and calcium. They can be purchased as a mixture, or with greater concentration of the specific deficiency requiring attention.
Lime is a readily available (in store or online) compound used to adjust soil pH levels upward or to correct calcium and manganese deficiencies, due to its high alkaline properties. You should avoid fertilizing and liming simultaneously, as they will cancel each other out and cause an unfavorable reaction in the soil. Made from pulverized limestone or chalk, lime comes in several variations; choose the form that most suits the needs of your marijuana garden:
- Hydrated lime (slaked lime). Very small amounts are needed to correct the pH level of your soil, as it is the highest alkaline form suitable for gardening. The chemical name is calcium hydroxide – Ca(OH)2.
- Garden lime is crushed limestone or oyster shells. The main component is calcium carbonate – CaCO3, which is also found in eggshells. This may be why eggshells are recommended as a component when making homemade compost. It will raise the soil pH levels and is less alkaline, thus safer to use than hydrated lime.
- Dolomite lime is high in magnesium. Dolomite has a neutral pH level of 7.0, which when mixed with the soil, creates the optimum pH levels for cannabis growth. Dolomite lime is available at local garden centers.
- Liquid lime blends with the soil quicker than the powders. Both garden lime and dolomite are available in liquid form.
Although unrelated to macronutrients found in NPK fertilizers, these micronutrients are still crucial to your plants. They support the many metabolic functions cannabis needs to develop properly, such as photosynthesis, protein synthesis, N fixation, and oxidation-reduction reactions.
Chelated minerals have bonded together by organic compounds and are necessary to a marijuana plant’s ability to transport oxygen and nutrients. Because minerals are inorganic, the chelating process facilitates absorption by plant life. Use them to correct certain mineral deficiencies, while correcting imbalanced pH levels.
The most common usage is liquid fertilizers targeting copper, iron, manganese and zinc deficiencies. Many hydroponic formulas contain a blend of chelated minerals. Single metal chelates are also available to address specific deficiencies in the marijuana garden.
In the beginning of this section, we mentioned the importance of amending soil with compost as a preventative measure in preparing the soil for your outdoor marijuana garden. Compost is a rich source of beneficial microbes and micronutrients providing a strong immune system for your cannabis crop.
Nutritious soil not only provides a healthy foundation for growth but supplies many insecticidal and anti-fungal properties, diminishing the possibility of blight thwarting your efforts. We will discuss compost in depth towards the end of this segment.
Obviously, you cannot add compost to a hydroponic system. However, you can still obtain the benefits of compost in a hydroponic environment with compost tea. However, special care must be taken when doing so. Use compost tea should as a foliar spray or add it directly in drip to drain systems.
Although compost tea can be applied at soil level in addition to its use as a foliar spray, we hope you are a conscientious gardener and have amended your in-ground or container grown plants with compost. As such, this particular discussion is geared towards the hydroponic gardener.
Compost tea is available for purchase through most hydroponic shops. They will either prepare the tea and sell it fresh, or offer kits to enable you to make your own. Or, if you have a green (brown, in this case!) thumb, we will offer a condensed version to create this nutrient packed food source for your soilless cannabis garden.
The kits available at your local hydroponic center will come with instructions, so there is no need for this article to duplicate the information provided on the packaging. Use this recipe to make a spray.
To make compost tea, assemble the following:
- 1 one gallon bucket w/handle
- Aquarium air pump with hose and bubbler attached
- 1 nylon stocking
- Organic, sterilized compost (buy at your local garden center if you don’t have a cured compost pile)
Fill the stocking with the equivalent of one quarter the bucket’s capacity. Tie the end of the stocking onto the handle and flip the loaded stocking into the bucket. Fill the bucket with water then place the air hose and bubbler in the bottom. Run the bubbler for a day in order to aerate the solution. When this step is complete, turn off the pump and let the tea settle. The liquid should be dark brown with no unpleasant odor.
Strain the mixture through cheesecloth and add to a spray bottle or add it to the irrigation water. Do not use it if it has an ammonia scent or smells rotten. Apply the spray within hours of aeration or it will lose oxygen, at which point you’ll be defeating the purpose; oxygen is the conductor enabling plants to receive nutrition.
Spread the unused compost on the soil around your marijuana plants (any plants, not just cannabis) and work into the soil or allow it to dry in the sun and return to the compost pile for future use.
Granite dust is a slow-release source of potassium and may contain other micronutrients that stabilize the alkaline levels in the soil. For maximum effectiveness, mix granite dust (rock dust) with a fifty percent mixture of compost. Till into the soil when preparing your cannabis bed.
When added to the soil, rock dust stimulates the growth of organic matter which feeds the beneficial microorganisms. An added benefit to incorporating rock dust in your plant bed is it results in holding the soil in place and conserving water. Rock dust carries the benefit of revitalizing the soil with minerals.
Greensand is the result of crumbling sandstone, a soft rock form rich in potassium and iron. It derives its name from the color and is not ‘sand’ per se. Greensand forms in marine environments and are typically rich in clay minerals and marine fossils. This is a slow-release application benefiting cannabis in the flowering stage. It is most beneficial when mixed with compost. (Are you beginning to see a pattern here?)
Hydroponic micronutrient products
These are available at any hydroponic supply house. Micronutrient products will correct deficiencies in copper, iron and various other micronutrients. Be aware that many products also contain levels of the necessary macronutrients, nitrogen, phosphorus and potassium. Read all labels to ensure proper balance of each nutrient when applying to your hydroponic marijuana garden.
See Chelated Minerals for more on this topic. Iron deficiency appears as a yellowing of the cannabis leaves, although the veins remain green. If your pH levels are correct, iron deficiencies are uncommon. When the need arises to apply an iron supplement, it is advisable to withhold using a fertilizer as they can counteract each other. Read the labels of both products before combining.
Kelp, otherwise known as seaweed, is useful in treating potassium and copper deficiencies. It is available in granular or liquid form. Kelp contains more than seventy vitamins, minerals and enzymes providing a wealth of health to the soil. Adding kelp to the compost pile aids in the decomposition process.
An added benefit is the deterrence of (unwanted) weeds in the marijuana bed. Kelp has been used for centuries as a soil amendment for all types of gardens. When using the liquid form, it is best to apply in the early morning or early evening and to avoid application when the temperature exceeds eighty five degrees.
This strange word means ‘fungus roots’. So why are we including this in the controls section? Mycorrhizae are an important component of soil life in the relationship they build with plant roots.
Essentially, Mycorrhizae fungi extract nutrients from microbes growing along the root surfaces and transport them to the roots. Mycorrhizae actually become an extension of the root system, working deep within the soil to provide nutrients and water to the roots, resulting in healthier marijuana plants. Mycorrhizae inoculants are available online.
Zinc is an enzyme aiding in the formation of chlorophyll. Zinc deficiency often is the result of the soil pH being too high. Too little zinc in cannabis will make itself known by producing smaller leaves than normal. Conversely, too much zinc is toxic and will kill the marijuana plant rapidly. Correcting the pH level of the soil often solves the problem. Foliar treatments are available if necessary.
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Rock phosphate is a naturally mined mineral often used as a soil amendment. It offers a slow release of phosphate, which is the second most abundant macronutrient essential to well-balanced soil in your cannabis garden. Check your pH levels before applying rock phosphate. It is usually only necessary as a soil amendment in pH levels above 7.0, which is optimal for Mary Jane’s garden to thrive.
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Final advice: Fixing nutrient deficiencies when growing weed
Fixing a nutrient problem in your plants depends on how well you recognize issues and when you attempt to fix them. Timing is important! Just before harvest is not the time to start thinking about a nitrogen deficiency. You must correct all nutrient deficiencies during the vegetative stage and properly flush your plant before harvesting. If you don’t fix the problem when the plant can make changes, you can’t expect your efforts to work!
FAQs about marijuana deficiencies
Deficiences typically appear as discoloration as an early sign. Look for yellowing leaves or brown/rust spots. The only exception is magnesium deficiency, which is tricky because symptoms of it don’t appear until 3-6 weeks after it has started. Other signs of deficiency include the curling and distortion of leaves, root rot, and finally, leaf decay.
Look in their leaves. The early signs of deficiency usually appear on the leaves of your plants. For more on the process of leaf checking, check out our cannabis leaf symptom checker.
Indoors, you should buy the right soil and know the pH level of the water you’re using. Outdoors, check the quality of the soil in your dedicated garden and use strong genetics. Germination is the most challenging part for outdoor setups, but ILGM has you covered with its high-quality seeds and guaranteed germination.
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Which cannabis nutrient deficiencies have you dealt with? Please feel free to share with us in the comments!