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Lack or excess calcium in the marijuana plant

Excess Calcium or Calcium Deficiency in Weed

Dear grower, when you decided to start growing your own cannabis, did you believe that you’d become an amateur plant scientist? This is what it takes to be proficient with growing your own high-quality marijuana. Ask any grower that’s been in the business, and they’ll tell you its takes in-depth knowledge to produce those High Times looking buds.

What’s the most challenging aspect of growing weed isn’t all the information you need to process, it’s coping with the problems you’ll eventually have. No one is perfect, and this means you’ll subsequently scan through Google searching “how to fix x.” Been there, done that, and now it’s your turn. Let’s look through one of the biggest hurdles for newbies and veterans alike: Calcium.

⚠️ What is Calcium?

Calcium is an essential secondary macronutrient. It doesn’t make the cut to hang out with nitrogen, phosphorous, and potassium; but it has a wide range of responsibilities in plant health. Its group of secondary nutrients consists of magnesium and sulfur, and these three aren’t needed in a large quantity as the primary nutrients NPK.

➕ Calcium’s Role in Cannabis Plants

Calcium’s role should never be understated. It’s responsible for keeping cell walls intact and sending messages to activate cellular activities. It’s crucial for many enzymatic processes in cannabis plants. It plays a crucial role in protecting cannabis plants from heat stress.

The list goes on and on, but we’ll leave it here for now. What we want you to understand most of all, is that calcium is an essential nutrient and is responsible for a wide host of aspects with marijuana plant.

Cell walls are responsible for keeping the body of a plant rigid and functioning. Imagine your own body, where our skin is made up of cell walls. If you suddenly managed to destroy your cell walls, then you’d immediately fall apart. The same goes for plants and its with utmost importance that they remain working.

Heat stress is a common problem in the grow room. If a plant lacks a protective measure to shield itself from the heat of an HPS or MH lamp, then it won’t survive for very long. Calcium allows for cannabis plants to regulate themselves so they may continue functioning even in hot climates.

Enzymatic functions are responsible for a plethora of activities in marijuana plants. Enzymatic functions allow for functions such as cloning, apical dominance, the creation of new shoots, and many more. Without these enzymatic functions, we wouldn’t be able to manipulate cannabis plants into growing outwards to create a SCROG setup.

Can you imagine what the cannabis industry would look like if we couldn’t clone? We owe many thanks to calcium for its critical role in the overall functions related to the production of marijuana crops.

✅ The Basics of Calcium While Growing Weed

Now that we have a basic understanding of calcium let’s take a look at what you need to know when you’re growing cannabis.

Calcium isn’t a mobile nutrient when growing cannabis. Mobility/immobility of nutrients plays a critical role in understanding how to identify a calcium deficiency or toxicity. Calcium’s immobility means that when there’s a severe lack or abundant amount, the affected leaves will be new growth at the top of the plant.

Cannabis generally uptakes a lot of calcium and depending on the substrate used, you may need more or less of it.

🔥 Calcium and Growing Medium

Calcium impacts cannabis grown in both soil and soilless mediums. Cannabis that is grown in soil generally has a natural buffer that is found in the mix. This calcium buffer is usually in the form of dolomite lime, which is powdered.

This buffer keeps the pH of the soil in check, and not allowing drastic swings toward too acidic or too basic. This necessary calcium buffer maintains the pH in the perfect range of 6.8-7.2. This is the reason why cannabis plants growing in soil generally don’t require a pH meter. This is also the reason why marijuana plants that are grown in soil usually don’t have high instances of calcium deficiency or toxicity.

On the other hand, cannabis plants growing in a soilless or hydroponic system generally has a higher instance of calcium deficiency or toxicity. The reason for this is because calcium is only available for uptake in a certain pH range. Growing in a soilless medium requires the use of a pH meter for this reason.

An especially important aspect when growing cannabis in soilless mediums is the cation exchange capacity. This chemical exchange is responsible for some of the most significant headaches growers encounter.

Cation exchange is the function of specific cations, like calcium, to be held by the medium. This means that if the cation exchange capacity of calcium is not functioning correctly due to an excess of another nutrient, the medium may hold onto the calcium ions. Calcium ions that are held by the medium will not be able to be utilized by the marijuana plant.

👾 What Does Excessive Calcium Do?

Too much calcium in your weed plants can lead to some severe consequences. The most obvious problem that you’ll see if you overdo it with a calcium additive is leaf burn. The cannabis plant is reacting to the excessive levels of calcium and is trying to push it out from the leaf tips. This causes necrosis (death) of the leaf tips, and they will be a yellow/brown color.

Besides causing leaf burn, excess calcium doesn’t actually create such drastic symptoms as a deficiency. Instead, too much calcium in your cannabis plants will actually lead to problems in other nutrients, such as magnesium and potassium. This situation presents a very frustrating problem when growing cannabis. Too much calcium will lock out magnesium or potassium, and the only way to correct the problem is by first dealing with the calcium issue.

So, although you’re experiencing potassium and magnesium related symptoms, the actual root of the problem stems from too much calcium. Dealing with an excess calcium problem doubles or triples your work by making it necessary for you to also try and fix your magnesium and potassium issues. It can also lead you astray chasing other nutrients, while the calcium problem remains active..

✨ How to Correct Excessive Calcium in Your Cannabis Garden?

Once you’ve determined that you have excess calcium in your marijuana plants, it’s time for a gentle flush. When I say gentle, I mean a low dose of a balanced nutrient mix. When growers here the word “flush,” they think pouring liters of water through the medium to flush every nutrient out. This is inadvisable because you’re suddenly depleting the cannabis plant of all of its necessary nutrients to function.

Flushing with a low dosage of nutrients allows excess nutrients to be pushed out while leaving a smaller concentration. This method allows your plants to continue taking up critical nutrients for its growth.

Alternatively, you can flush your plant with a low dose of calmag, a combination of calcium and magnesium. By flushing with calmag, you decrease your chances of suddenly locking out potassium and magnesium.

Ata Calmag one of the most effective products when your plants need an extra supply of Calcium and Magnesium…

⛳ What Does a Calcium Deficiency do?

A calcium deficiency is much more noticeable than toxicity. A calcium deficiency will always begin in new growth and the top half of the cannabis plant. The reason for this is because of calciums immobility, and this means it won’t travel to older leaf growth. So, a clear indicator of spotting a calcium deficiency is by evaluating what portion of your plant is being affected.

Visual indicators are light yellow and brown spots that look similar to rust. These spots will generally start near the edge of the leaves or near the veins. As the deficiency expands, these mottled colors will begin to envelop the entire leaf. New leaves will usually curl, and the topmost area of growth will slow down in vigor. Stems will suddenly become flimsy and fall off easily if brushed against. The overall growth of the plant will slow down drastically

A calcium deficiency in cannabis also drastically limits the plants’ ability to fight off pathogens and predators. This means that certain types of fungi and bacteria will be more likely to establish themselves in this time of weakness. Pests such as mites, whiteflies, and gnats will be readily attracted to plants that are already weak and unable to defend themselves.

Since cell walls are weak during a calcium deficiency, the overall plant’s wall structure is fragile. This makes the entire plant brittle and unable to support the weight of buds. Bud development is reduced, as well as the growth of the plant’s root system.

Also, calcium plays a significant role in helping a cannabis plant cope with heat stress. While a calcium deficiency is ongoing, a marijuana plant will be unable to cope with heat stress. This is compounded by the fact that the cell walls are already weakened.

⭐ How You Can Fix a Calcium Deficiency?

Now that you’ve spotted enough symptoms that’s lead you to believe you’re looking at a calcium deficiency, it’s time to act..

First, you’ll need to analyze the nutrients that you’ve been feeding your plants. Are you giving lower doses than what’s recommended? Are you checking pH? These should be the first questions that you answer.

If you realize that you are giving too small of a dose of nutrients, then it’s time to bump up your schedule. Start with a small increase of 10-15%. Allow 2-3 days to notice if the new leaves resume vigorous growth..

Another option is to use calmag specifically in addition to your current nutrient lineup. In this situation, it’s recommended that you cut the recommended dosage of your calmag in half. That means if your calmag bottle suggests 5mL per 4 liters, then cut it to 2.5mL per 4 liters.

If you realized you haven’t checked pH, then its time to do so. If you recognize that your pH is off in the too acidic or basic direction, then it’s time to correct your nutrient pH. You should be aiming for 6.8-7.2 in soil and 5.2-5.8 in hydro. Once you’ve adjusted your pH, then it’s time to start adding nutrients at the right level.

Of course, you won’t be seeing a change instantaneously. Patience is key in growing excellent weed, and when dealing with problems, patience is a virtue. If problems persist after 4-7 days, it’s time to increase the dosage of calmag or your base nutrient.

Infographics about Lack or excess of calcium in your marijuana plant

⚠️ Conclusion

Now you’ve learned why calcium is such an important nutrient, even though it’s called a secondary macronutrient. Calcium plays a wide amount of roles, and they are all necessary for the health and happiness of your plants. If you grow your cannabis with the objective of keeping all of these necessary nutrients in line, you’ll have a problem free grow.

Of course, having a problem free grow takes either a lot of luck or a high degree of experience. As a grower, you must keep your plant’s system well fed if you want it to produce high-grade cannabis. Having the necessary knowledge of the things that run your plant is crucial, and you’ll be a better grower for it.

For more information on growing cannabis, join us at PEV Grow to discover a wide range of topics, from nutrient issues to various growing systems.

Get the right level of calcium for your cannabis plants ⭐ Avoid excess or deficiency in your marijuana crop ⭐ Everything you need to know!

Calcium Deficiency

by Nebula Haze & Sirius Fourside

Problem: Calcium is an important nutrient which helps provide structure to the cannabis plant and helps it withstand stress like from heat. When your plant has a calcium deficiency, the main symptom that you’ll be able to notice is brown or bronze splotches or spots on your leaves.

A cannabis calcium deficiency can sometimes be difficult to diagnose since calcium deficiencies are often accompanied by magnesium, iron, and/or other cannabis deficiencies.

Calcium moves relatively slowly through the plant (it is a semi-mobile nutrient), which means it tends to “stay put” after it’s been given to a leaf. It tends to show up on leaves that are actively growing and getting some amount of light.

Calcium deficiencies most often show up in the following places:

  • Newer growth (upper leaves)
  • Parts of fan leaves that have been exposed to the light

Found near the top of the plant under the light

This lower fan leaf is mostly in the shade, but the calcium deficiency appears near the edges that are getting light. Calcium deficiencies often show up on parts of the leaf that are still actively growing.

Calcium Deficiencies Appear on New or Actively Growing Leaves

Calcium deficiencies tend to appear on newer or growing leaves, which means calcium deficiencies first appear on leaves where there’s rapid vegetative growth.

Some of the most noticeable signs of a calcium deficiency will appear on newer or growing leaves which may display:

  • Dead spots
  • Crinkling
  • Spotting / Mottling
  • Small brown spots
  • Stunted growth
  • Small or distorted new leaves
  • Curled tips
  • Leaf die-off
  • Affected leaves may appear green besides the spots

Here’s a close-up of a calcium deficiency that appeared on leaves towards the top of a cannabis plant grown in coco coir:

Other Symptoms of Calcium Cannabis Deficiency

If a cannabis plant is affected by a calcium deficiency for too long, it may begin to show the following symptoms due to the lack of calcium.

  • Stems become weak or flimsy and may crack easily
  • Stems become hollow or show inner signs of decay
  • Plant does not stand up well to heat
  • Flowers/buds do not develop fully, or development is slow
  • Roots appear weak or under-developed
  • In severe calcium deficiencies, parts of roots may even die off or turn brown
  • Roots are more susceptible to root problems like slimy root rot

Cannabis tends to like high levels of calcium, so it is unusual to feed too much calcium when using normal amounts of nutrients and/or regular soil. There are not many known cases of cannabis calcium toxicity (too much calcium), however too much calcium can cause the plant to lock out other nutrients, so it’s important not to go overboard..

Calcium deficiencies are more likely to appear when…

  • Grower is using filtered or reverse osmisis (RO) water to feed plants – the amount of calcium found in tap water varies, but some tap water has enough calcium to prevent calcium deficiencies
  • PH is Too Low – If grow medium is acidic (below 6.2 pH, Calcium can get locked out even if the Calcium is physically there)
  • Growing cannabis in hydroponics or coco coir without supplementing extra Calcium (it’s recommended to use a Calcium supplement in hydro or coco)
  • When growing in soil that hasn’t been supplemented with calcium (usually from dolomite lime)
  • Too much potassium can also sometimes cause the appearance of a calcium deficiency
  • Outdoors – calcium deficiency is more likely to appear in acidic soil (below 6.2 pH)

Different strains of cannabis tend to have different nutrient problems. Some cannabis strains (or even specific plants) tend to use much higher levels of calcium than others, and so you may see calcium deficiency problems with one plant even when all the other plants (which are getting the same nutrients and environment) aren’t showing any signs of deficiency.

Solution For Calcium Deficiency in Cannabis

Your cannabis plant may show signs of a calcium deficiency if the pH at the roots is too high or too low. That is because when the pH of your root zone is off, your cannabis cannot properly absorb calcium through its roots. Therefore the first step is to ensure that you have the correct pH for your growth medium. Learn more about pH and cannabis.

Please note: After a calcium deficiency is cleared up, the problem (brown spots and unhealthy new leaves) will stop appearing on new growth, usually within a week. Please note that leaves which have been damaged by a calcium deficiency will probably not recover or turn green, so you want to pay attention to new growth for signs of recovery.

  • In soil, calcium is best absorbed by the roots in the 6.2 – 7.0 pH range (in soil, it’s generally recommended to keep the pH between 6.0 – 7.0, but calcium specifically tends to be best absorbed above 6.2)
  • In hydro, calcium is best absorbed by the roots in the 6.2 – 6.5 pH range (in hydro, it’s generally recommended to keep the pH between 5.5 – 6.5, but calcium specifically tends to be best absorbed above 6.2)

If you suspect your growing cannabis plant has a calcium deficiency, flush your system with clean, pH’d water that contains a regular dose of cannabis-friendly nutrients that includes calcium. This will remove any nutrient salts that may be affected the uptake of calcium and help restore pH to the proper levels.

To supplement with extra Calcium… (it’s very rare to give a cannabis plant too much calcium, however, too much calcium can lock out other nutrients so don’t go overboard)

Calcium and magnesium deficiencies often appear together in cannabis. Many growers decide to purchase some sort of Calcium-Magnesium (often called Cal-Mag) supplement for their grow room in case this common deficiency appears.

Listed below are common cannabis Calcium supplements, along with some general information about each one. After supplementing with Cal-Mag and correcting the pH, you should expect to see new healthy growth within a week. Remember, the old leaves will probably not recover, but new growth should be green and healthy.

CaliMagic is Well Suited For Hydro, Coco Coir, or Soil

General Hydroponics CaliMagic is a calcium and magnesium plant nutrient supplement. General application is to mix 1 tsp (5ml) of CaliMagic into each gallon of water. I have used Calimagic several times with great results.

Dolomite Lime – For Soil Growers (Organic)

If you’re looking for a way to supplement calcium in your organic or soil setup, I highly recommend a product called “Dolomite Lime.”

Dolomite is a good source of calcium and magnesium and can be mixed with your soil. The great thing about dolomite is it works slowly over the course of a few months.

Dolomite has a neutral pH of about 7.0 and will help keep soil at the correct neutral pH range which is optimum for cannabis growth.

You can buy Dolomite Lime online, but with shipping, it’s almost always waaaay cheaper to pick up a bag at a home improvement or gardening store such as Lowes, Home Depot, gardening centers, etc. If possible, try to get a finer grade of dolomite compared to something that is more coarse.

How to Use Dolomite Lime for Cannabis: When growing cannabis indoors, add 6-7 teaspoons of fine dolomite lime to each gallon’s worth of soil. So if you’re mixing enough soil to fill a 5 gallon container, you want to add 30-35 teaspoons (about 2/3 cup) of dolomite lime to the mix. Mix the dolomite lime and the dry soil thoroughly, then lightly water it with water that has been pH’ed to 6.5. After getting the soil wet, mix the soil well and wait a day or two to let the soil settle before checking the pH and adding plants. When growing in an outdoor garden, follow the dolomite lime manufacturers instructions.

If you cannot get rid of your calcium deficiency, please consult our 7-Step Cure to 99% of Cannabis Growing Problems

Plant Symptoms

  • Bronze or brown patches
  • Brown or slimy roots
  • Brown or yellow leaf tips/edges
  • Buds dying
  • Buds look odd
  • Bugs are visible
  • Curling or clawing leaves
  • Dark leaves
  • Drooping plant
  • Holes in leaves
  • Mold or powder
  • Pink or purple on leaves
  • Red stems
  • Shiny or smooth leaves
  • Spots or markings
  • Twisted growth
  • Webbing
  • Wilting leaves
  • Yellow between leaf veins
  • Yellow leaves

This page is part of our Plant Doctor series. You can use our tool to filter by symptom and help diagnose your plant.

Calcium deficiencies cause tiny brown spots that appear on new and middle growth. Learn how to fix this problem for good!