How to Treat Copper Deficiency in Cannabis Plants?

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Added 27 January 2023

Your cannabis plant does not need large amounts of copper, but even in trace amounts, this mineral is crucial for your plant’s health and growth. In fact, it is one of the minerals that help the buds grow bushy and aromatic. 

But sometimes, your plant may fail to get the right amount of copper, which can create various problems for your plant. How can you treat this problem and avoid it in the future? Keep reading to know all about copper deficiency, its causes, and the best treatment methods.

How Does Copper Deficiency Affect Cannabis Plants?

How Does Copper Deficiency Affect Cannabis Plants?

Copper is not a macronutrient, but it is still necessary for the healthy growth of your cannabis plant, especially during the flowering stage. It helps the buds develop flavor and color, which is crucial for many users. 

Additionally, copper also aids in the respiration and photosynthesis processes of the plant, helps in the production of enzymes, and is also a vital nutrient for sugar and protein metabolism. 

But when your plant does not get enough of this micronutrient, it can face various issues related to the production of energy and enzymes, which can affect the plant’s growth in various ways. And during the flowering stage, a lack of copper can hamper bud development, leading to subpar buds that lack flavor and potency. 

If the copper deficiency (Cu deficiency) is not fixed on time, it can not only lead to slow or stunted growth of the plant but also impacted yield. In severe cases, this problem can completely ruin your plant’s yield. Your plant may still grow buds but they will lack flavor and look unappealing.

How to Identify Copper Deficiency in Cannabis?

How to Identify Copper Deficiency in Cannabis?

Copper is an immobile nutrient, i.e., it does not move around within the plant. Once it reaches a part of the plant, it stays there. So, if your plant is experiencing copper deficiency, the symptoms will first show up on new growth like young leaves.

You’ll notice the young leaves turning dark with purple or blue undertones as they fail to produce chlorophyll. And as the leaves turn dark, their tips and edges may turn white or yellow, and the leaves may also appear shiny or metallic. In some cases, young leaves can also start rolling under due to copper deficiency. 

Leaves show the first signs of damage but that’s not all. If the problem is not fixed, other symptoms start showing up, such as the following:

  • Weakened stems and branches as the plant fails to synthesize lignin (the protein that’s a crucial part of stem cells) due to a lack of copper
  • If your cannabis plant is in the flowering stage, even your buds will get affected by copper deficiency. Here, the buds may ripen slowly or not at all
  • There can also be an undergrowth of pistils at the nodes

Do note that during the late flowering stage, it is normal for some leaves to turn yellow and fall off, but if this happens at an unusual rate or is accompanied by other symptoms, you need to act quickly. 

Copper Deficiency vs Nutrient Burn

Copper Deficiency vs Nutrient Burn

While copper deficiency is easy to spot, many new growers end up mistaking it for nutrient burn — the symptoms are quite similar. So, you need to understand how copper deficiency differs from a nutrient burn.

For example, if your plant is experiencing a nutrient burn, the first symptoms will appear on the leaves — the tips will start turning yellow. Over time, the leaves will turn brown and dry. With a copper deficiency, the leaves will first turn white or yellow. 

Another difference between the two problems is that in copper deficiency, the leaves will develop a purple undertone, look shiny, and the tips will appear in stark contrast to the leaf's body. 

It is crucial that you distinguish the two, or you risk working to solve a problem that doesn’t exist while overlooking the one that does. 

What Causes Copper Deficiency in Cannabis?

What Causes Copper Deficiency in Cannabis?

While copper deficiency is not so common, it can cause significant damage to your cannabis plants. This is why you need to fix the problem ASAP. But before that, you need to figure out what is causing the problem.

Here are some of the common causes of copper deficiency in cannabis.

  • pH Imbalance in the Root Zone

The most common cause of most nutrient deficiencies is pH imbalance in the root zone and it can cause copper deficiency, too. When the pH in the grow medium is beyond the ideal range, it can inhibit the roots from absorbing copper properly. 

  • Nutrient Lockout in the Root Zone

Copper deficiency can also occur if there is salt buildup around the roots, which may stop the roots from absorbing copper. For example, excess iron, aluminum, or manganese can affect the roots’ ability to absorb copper.

  • Lack of Copper 

Your plant won’t get any copper if there isn’t any copper in the soil. This is unlikely because copper is only required in small quantities, but if your soil is of low quality or if you use RO water, a lack of copper can be a cause of concern.

  • High Organic Matter in the Soil

Copper binds easily to organic matter, which can sometimes affect its solubility and availability to the roots. So, you need to ensure that all the organic matter in the substrate is decomposed well so they don’t get bound to copper. 

Additionally, you need to keep your soil free of harmful bacteria, fungi, and viruses as they can also affect the roots’ ability to absorb copper.

  • Wrong Growth Environment

In rare cases, copper deficiency can also occur if the grow room environment is not right, especially the temperature, relative humidity, and carbon dioxide levels. 

How to Treat Copper Deficiency in Cannabis Plants?

How to Treat Copper Deficiency in Cannabis Plants?

Now that you know what may have caused a copper deficiency in your plant, let’s move on to the most effective treatment methods, which are as follows.

  • Flush the Plant

The most probable cause of copper deficiency in your plant is due to wrong pH or salt buildup in the root zone. So, you first need to flush the plant with RO water. Flushing will clear the substrate of any minerals.

Once the plant is flushed, you need to fix your nutrient solution’s pH — it should be 6.0 to 7.0 for soil-based cannabis and 5.5 to 6.5 for hydroponic cannabis. If the pH is far off, you can use pH up/down solutions to correct it.

Then, feed the plant the solution and check the pH of the runoff water — it should be in the same ballpark as the pre-fed solution.

  • Supplement Copper to Your Plant

Sometimes, you may need to supplement copper to your plant. And it is quite easy to do because your plant only requires copper in small quantities. 

To supplement copper to your plant, you can use copper fungicides that contain copper sulfate or chelated copper, but these may only work as a copper boost instead of a long-term solution.

For a long-term solution, you can use compost, kelp, or greensand as they are all rich in copper. 

But there’s an old farmer’s trick that you can use if you don’t want to rework the entire nutrient routine for copper — it’s only needed in trace quantities, after all. You can use copper coins!

Simply add a few coins that contain copper, like 1p or 2p in the UK and quarters in the US, to the water for a night and feed it to your plant the next day. Just don’t use coins like US pennies as they contain a lot of zinc but not enough copper.

These two methods should fix the copper deficiency in your cannabis plant. However, note that some affected leaves may never recover. If they have completely lost their color, you should consider pruning them and preparing for new growth.

How to Prevent Copper Deficiency in Cannabis?

How to Prevent Copper Deficiency in Cannabis?

Do you know what’s easier than treating copper deficiency in cannabis? It’s preventing copper deficiency. Doing so is straightforward. Follow these tips to prevent copper deficiency in your cannabis plant:

  • Always maintain the pH levels of your nutrient solution and the root zone — this will help you prevent most nutrient deficiencies
  • Use high-quality soil and nutrients that are rich in copper among other nutrients 
  • Your cannabis plant is sensitive to water, so use the correct type of water that contains minerals — tap water is your best bet 
  • Avoid overwatering your roots as this can wash away the copper and at the same time, do not overfeed your plant as it can create nutrient lockout

Follow these steps, keep your plant healthy, and you may never have to worry about copper deficiency ever again in your cannabis garden.

Summary: How to Treat Copper Deficiency in Cannabis Plants?

Isn’t it easy to fix the copper deficiency in cannabis? All you have to do is know what is causing the problem, which is usually wrong pH, nutrient lockout, or lack of copper in the soil. 

Once you know the problem, all you have to do is flush your cannabis plant, rebalance the pH of the soil and solution, and sometimes supplement copper, which you can do so with fungicides that contain copper, copper coins, or compost. 

But in any case, ensure you follow the recommended tips to avoid copper deficiency in the first place. The problem, while it may appear small, can cause significant damage to your plant’s yield and must be avoided.


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