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1. Copper Deficiency in Cannabis

Copper deficiencies are one of the less frequently seen problems in cannabis cultivation, but that doesn’t mean they can’t pop up from time to time. While less common than say, a nitrogen or calcium issue, they can still have a major impact on the health of your plants.

Copper is typically available from the environment, but if the soil or water used to grow your cannabis has become depleted of copper over time, then your crop may begin to suffer. Copper is one of the many micronutrients (the nutrients required in small doses) that are essential for healthy plant growth. It is important to understand the symptoms of copper deficiency in cannabis so you can properly identify the issue, and so you can know what the correct steps are to take in order to resolve the concern.

Early detection, identification, and treatment will guarantee that your plants bounce back in no time at all. The yield should be unaffected, as long as the issue is caught and treated early.

PRO-TIP: Copper deficiencies are more often caused by a pH imbalance in the root zone than an actual lack of copper in the substrate. We will discuss this further later on in the article.

What Is Copper, And Why Is It Important For Cannabis Crops?

Copper is just one of the many micronutrients vital for healthy cannabis growth and development. It plays a key role in a bunch of metabolic processes and helps to ensure the correct uptake of other essential nutrients. It is also involved in chlorophyll formation and plays an essential role in photosynthesis. It is also a vital component of seed production, although if you are growing weed for the dank, stanky flowers then you won’t be worrying about this.

Plants that have correct levels of copper in their environment will have higher resistance to disease and be more productive. Without the right levels of copper, your crops may begin to suffer from stunted growth, and discoloration – or in severe cases, the crop can die.

What Are The Signs & Symptoms Of Copper Deficiency In Cannabis?

The most common symptom of copper deficiency in cannabis is the tips and edges of the leaf growth turning a pale yellow (or even white). This is combined with a darkening of the inner part of the leaves, or even an almost blueish hue appearing in more extreme cases. The edges of the leaves may also curl downwards, and you may find that your plants are not growing as quickly or robustly as usual. When left untreated, a bad copper deficiency can result in the foliage dying off completely.

If the crop has already reached the flowering growth cycle before the copper deficiency begins, you will likely notice the buds forming much slower than expected, or a complete pause in flower production.

Some other common symptoms of a copper deficiency in weed plants are:

  • The leaves take on a shiny, almost metallic-like sheen
  • The leaves become stiff, slightly more brittle, and may roll inwards and downwards
  • It most commonly affects the leaf growth closest to the lights
  • Copper deficiency is often confused for nutrient burn, as the yellowing tips and edges of the leaves closely resemble over-feeding. With copper issues, the tips and edges shouldn’t turn brown or crispy after they turn pale yellow, which is a clear way to tell the two issues apart.

So, you most likely have a copper issue if

  • if leaves closest to the lights are displaying pale yellow to white tips and edges
  • the inner sections of the leaves are darkening, even turning a blue-to-purple hue
  • the leaves are slightly stiffening, curling inwards, and taking on a slight metallic shine
  • the overall plant robustness seems to have dropped
  • look for wilting, weakened branches and main stem, and growth abnormalities.

What Are The Most Likely Causes Of Copper Deficiency?

Now this is where people sometimes get a little confused.

It is just common sense that a copper deficiency would most often arise from a lack of copper in the environment, or substrate, right?


There is a wide range of factors that can cause copper deficiency in cannabis. The most common cause is an incorrect pH balance within the root zone.

If the pH of the soil or water your cannabis plants are growing in slides outside the ideal range, then certain essential nutrients (including copper) will become much harder for your crops to absorb. 

The ideal pH range is dependent on your style of cultivation.

  • Soil-based substrates should be watered and fed in the range of 6.0 to 7.0 pH
  • Hydroponic crops (coco-coir included) need a slightly more acidic root environment, typically between 5.5 and 6.5 pH

It’s not just pH that needs to be considered, though.

Over-feeding can also result in copper deficiency. 

The feed levels need to be monitored throughout the entire grow, especially for hydroponic crops. Novice cultivators typically fall into the thinking of “a little more is better” when it comes to feeding their crops, but the opposite is actually the case. Over-feeding can result in a build up of both macro and micronutrients, which results in competition between the two for absorption. The excess of macronutrients will be favored by the plant over the copper, leading to a deficiency. This is known as nutrient lockout.

So, make sure you are giving your crops just the right amount of nutrients, and that you keep an eye on the pH level at all times – as this is where most issues with copper deficiency arise from.

Diseases can also result in certain deficient issues, including copper. If the crop is suffering from disease, the plant will begin focusing all of its energy on combatting this issue – and the uptake of other essential nutrients may begin to suffer.

The environment in which the crop is grown also has an impact on nutrient absorption rates. If the environment is too cold, the lights are too close to the canopy, or the humidity and temperature ranges are out of whack then the plant won’t be able to absorb all of the copper it needs to thrive.

One thing to keep in mind is that certain cultivars are more prone to copper issues than others and that it usually builds up quite slowly over time, meaning it is not often life-threatening for the crop, and that it can be rectified in most cases.

Although copper deficiency is one of those issues that can take some time to diagnose, it is not actually that hard to fix and can be done with a few simple steps.

But before we dive into the best ways to treat a copper deficiency, let’s first look at the best practices to prevent one from occurring in the first place.

How To Best Prevent A Copper Deficiency

First things first. As we already mentioned, pH issues are usually at the heart of deficiency issues. To prevent your crop from experiencing copper deficiency due to incorrect pH levels, you need to make sure that the water or soil your plants are growing in has a pH as close to the ideal range as possible.

Keeping your pH levels in check is easy, but it does require some regular monitoring. pH meters are the most accurate way to measure the acidity of your root zone. You will want to check the pH of your feed water or nutrient solution before every watering, and make sure it is within the desired range. If not, you can make the necessary adjustments to bring it back in line. If you suspect that the root zone has a pH level that is too high or low, you can use the pH meter to check the run-off from your pots after watering. This will give you some idea of what the root environment is like.

The next thing to consider is avoiding over-feeding your crop. This is more of an issue for growers using hydroponic methods, as organically soil-grown crops are rarely subjected to over-feeding problems as the soil-grown plants will essentially only take what they need from the soil, and no more. This is a huge simplification, but I’m sure you get the gist.  

But if you are growing in water or using a coco coir substrate, then it is wise to keep an eye on the EC or TDS levels of your feed water. Keep in mind that nutrient companies are businesses, and they make their cash by selling more nutrients. So, we always suggest starting out with around a quarter to a half of the recommended feeding levels displayed on the bottles, and then working your way up from there.

Finally, try to make sure that the environment in which you are growing is as ideal as possible. Keep the lights at the correct distance from your canopy, keep temperatures and humidity levels within range, and make sure that your air circulation is up to scratch. All of these environmental factors will have an impact on nutrient absorption rates, so make sure they are kept as close to optimal as possible.

How To Treat A Copper Deficiency

Ok, you have identified that your crop is suffering from copper deficiency. What now?

The first thing to do is to flush the root zone with fresh, pH-balanced water. This will not only help balance the pH back into the correct range but also help clear out any excess nutrients that could be competing with the copper for absorption. This goes for pretty much all the nutrient deficiency issues that can strike cannabis crops, so flushing is always a pretty good idea for a first step, no matter what you may think the issue is. 

When flushing a cannabis plant, you want to look for around 50% of the water to drain out of the pot. If you are growing in soil or coco-coir, we suggest using about double the amount of fresh aqua as you would for regular watering. For hydro, you can exchange the tank’s feed water with fresh, pH-balanced water for a day or so, and then slowly re-introduce the nutrients.

Once you have flushed the root zone, it is time to build up that nutrient base level again. For soil growers, this is less of a problem, as even very well-flushed soil will hold onto a good level of nutrients. Depending on the stage of growth, you may want to give a very light feed for the first few days.

But for hydro and coco-coir growers, this is an essential step to ensure that the plant has all the macro and micronutrients it needs for healthy growth. All hydroponic growers need to have not only a pH meter but also a nutrient meter (EC or TDS). This will help make sure that you are giving the plant just the right amount of nutrients, in line with its age and stage of growth.

If you are sure that the issue has popped up due to low levels of copper in the root zone, then you should still give the plants a good flush before adding any copper supplement. This is because too much copper can also cause deficiencies in other essential nutrients – so it is better to start with a clean slate and then add a light dose of copper supplement along with the regular feed.

If the plants are showing signs of disease, then it is best to try to treat the disease before adding a copper supplement to the feeding regime. Copper treatments are usually best used as a preventative measure, rather than a cure.

How Long Will It Take To See Results?

It often takes around two to three weeks to see an improvement in the symptoms of copper deficiency. But it is important to understand that copper is classed as a low mobility nutrient, and so it can take some time for the treated plants to absorb enough copper from the root zone and show signs of improvement.

Recovering cannabis

Even then, affected leave growth may never fully recover and will only reach a certain level of improvement. That being said, copper is an essential nutrient in the growth of cannabis plants, so it is still important to make sure that your crop has enough copper in its root zone for optimal health and growth.

You can also look into using a fungicide spray that incorporates copper as an active ingredient. This way, your plants get a direct dose of copper, and the fungicide properties will help to reduce any other issues that could be causing the deficiency, but make sure that you never spray directly onto flower growth. This will result in the flowers dying. 

What to Expect From A Cannabis Crop That Has Recovered From Copper Deficiency?

Once your crop has recovered from copper deficiency, you can expect to see an improvement in overall vigor and plant health. Copper is an essential nutrient that helps to fortify the leaves and stems of your plant, so you will notice an improvement in the growth rate in your crop. But don’t expect them to bounce back 100%, and certainly not instantly.

When it comes to yield, it is very hard to say what you can expect from a crop that has recovered from copper deficiency. If the crop is still in vegetative growth when the issue pops up and is dealt with quickly, then you should be able to expect a similar yield to an unaffected crop.

However, if the copper deficiency is severe, or strikes during the flowering period and is left unattended for more than a week or so, then you can expect a fairly large drop in yield. Try to keep an eye out for copper deficiency and treat it straight away, as this can be the difference between hitting the harvest window or missing it altogether. 

Some growers will just let the crop develop for a week or two longer than it had been unaffected, but this is not a guaranteed way to make up for lost yield, and will most likely change the cannabinoid profile slightly. THC degrades into CBN when allowed to grow past the expected harvest date.

In Conclusion

If you find yourself dealing with a copper deficiency, just remember to take it slow and follow all the steps outlined above. While it can take a heavy toll on your plants, it is anything but a death sentence if you catch it in time. Just keep an eye on your nutrient levels and make sure that your pH range is not too high or low, and you should have a healthy crop of cannabis on your hands in no time.

If you are looking to get the absolute best in worldwide cannabis genetics, you have come to the right place. Here at Premium Cultivars, we have the most comprehensive range of new, classic, and exotic strains to choose from, and our team is standing by to help you find the perfect strain for your needs.

Picture of Ed Rushford

Ed Rushford

Ed Rushford’s impact on cannabis growing is undeniable. Though he tends to focus primarily on 2 areas, plant training techniques and dealing with disease, pests, and other problems, he has offered many insights into how cannabis plants live and grow. That’s not to say that Ed is unfamiliar with the complete life cycle of cannabis, from seed to harvest, but he uses his widespread knowledge to hone in on the minutia and niche areas of growing cannabis. Ed’s goal is to spread knowledge and allow for everyone to become better growers. 𝕏

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