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Nutrient Lockout in Cannabis Plants: How to Identify, Fix, and Prevent

by | Sep 12, 2022 | Cannabis, Environmental Threats, Getting Started, Nutrients, Troubleshooting

Nutrients for cannabis plants are essential to the plant’s health. Nutrients can be mobile or immobile, and nutrient lockout is caused when your growing cannabis doesn’t have enough of either nutrient. So what does nutrient lockout look like? Well, it will show up as yellow leaves with brown spots on them, wilting plants, stunted growth, and nutrient deficiencies in other areas of the plant that you might not even think about – just to name a few symptoms. Luckily there are things that you can do to prevent and fix nutrient lockout and we will detail them for you below.

What are nutrients for a cannabis plant?

All plants need nutrients and cannabis plants are no exception. Nutrients are the building blocks of the plant, without them, your cannabis plants won’t grow. There are many different kinds of nutrients that your cannabis plant will take and there are many different brands of nutrients available at most garden centers. Some of the nutrients necessary for cannabis plants include nitrogen, phosphorus, and potassium, known as “NPK”, and you will see these listed as numbers on most nutrients, for example as 4-4-4 or 3-9-2. Other nutrients are available in liquid nutrient formulations that are easy to use.

What are mobile and immobile nutrients?

Mobile nutrients are ones that can change places within the plant, whereas immobile nutrients cannot. Mobile nutrients include nitrogen and phosphorus while potassium is an example of an immobile nutrient. This means that your cannabis plants will take up all three kinds of these nutrient types at different times during their life cycle.

Mobile nutrients are those that can be easily transported around the plant to other parts where they might not have been taken up originally. An immobile nutrient is something like nitrogen or calcium which cannot be moved once it has been put into place by the roots so your plants will need more of them than a mobile nutrient. If a nutrient is locked out of the plant, it cannot be moved to where it’s needed and this will result in nutrient deficiencies throughout your cannabis plants as well as nutrient lockout.

What is nutrient lockout in cannabis plants?

Nutrient lockout can happen for several reasons but most often it happens because there is a nutrient deficiency in the growing cannabis plant that isn’t provided by the growing medium which results in a lack of nutrients. When there is not enough nutrients, your plants will show signs and symptoms that clearly state their nutrient needs so you can give them what they need to be happy and healthy plants. Nutrient lockout can also be caused by excess nutrients, but it is mostly caused by nutrient deficiencies. If you are being affected by nutrient lockout, you will have nutrient deficiencies in other parts of the plants as well since they cannot use nutrients that aren’t available to them.

Often, nutrient lockout will happen because nutrient salts are building up in the soil and inhibiting nutrient absorption. When nutrient salts build up in the soil, they will accumulate and cause nutrient deficiencies. Eventually, your cannabis plants won’t be able to get enough nutrients and nutrient lockout will result.

The PH of your soil and water are crucial because phenol toxicity or pH lockout-related problems looks like nutrient lockout . Phenolic lockouts are caused by nutrient salts building up in the soil causing excess salts, which inhibits nutrient uptake. The pH may also be too high or low to absorb nutrients properly. This nutrient lockout will often look like nutrient burn, but it is caused by different factors than nutrient deficiencies and toxicity are and is due to the high salt content of the soil.

What are the symptoms of nutrient lockout in cannabis plants?

The signs of nutrient lockout that your marijuana plants will display when they have it are yellow leaves with brown spots on them, wilting plants, stunted growth, and nutrient deficiencies. Leaf burn is also a common symptom. Nutrient deficiencies can look like any number of nutrient deficiencies for other kinds of plants, so it can be difficult to tell the difference. If you are unsure what nutrient deficiency your cannabis plant is suffering from, you should look at them under a magnifying glass or take pictures and contact your local garden center, if legal, for assistance in figuring out exactly what nutrient they need. There are also many charts and forums online that will gladly help you diagnose your deficiency, nutrient lockout, or nutrient excess.

How do I diagnose nutrient lockout in my cannabis plants?

The easiest way to identify and diagnose nutrient lockout is to look at nutrient deficiencies in your cannabis plant. If there is a nutrient deficiency present, it will show up on the parts of the plants that need those nutrients most and these nutrient areas might not be exactly where you would expect them to be if you are new to growing or have never had nutrient lockout before.

How do I fix nutrient lockout in my cannabis plants?

Fixing nutrient lockout is easy but will take time. Make sure you stop all nutrient supplements for a minimum of two weeks so your cannabis plant’s own natural nutrient uptake system has time to correct itself and take over again. Then nutrient flush your plant by giving it nutrient-free water. You will also want to flush the plant with only pure, pH’ed water for a period of time of up to two weeks. This will ensure that nutrient buildup isn’t the problem and your supplements are not at fault for nutrient lockout and remove any salt buildup that could be causing nutrient lockout.

How do I prevent nutrient lockout in my cannabis plants?

There is no way to completely prevent nutrient lockout but there are ways to reduce its likelihood of happening or at least make it easier to recover from should the problem take place. It’s important not to give nutrient supplements in excess of what your cannabis plants can absorb. It’s also important that nutrient supplements are given with the correct nutrient at the correct nutrient levels, pH levels, and at the proper times during the growing cycle for optimum results. Nutrient lockouts most often happen because people try to grow their own weed without doing research about nutrient lockout, nutrient deficiencies, or nutrient supplements. If you are not sure about what kind of nutrient supplement to give your cannabis plant at any given time or how much they need based on the stage they are in during the growth cycle, look online for accurate information before giving them anything else. Give nutrients only when you know it’s safe and effective for your cannabis plant and make sure you are giving the right nutrient at the right time for your particular kind of cannabis.

What other problems look like nutrient lockout in cannabis plants?

Many nutrient deficiency symptoms look alike, so it can be hard to tell nutrient lockout apart from other cannabis problems. The most common nutrient problem that people mistake for nutrient lockout is a magnesium deficiency. Magnesium deficiencies are often caused by overwatering plants, and they will show signs of chlorosis, which is yellowing between the veins on leaves. Other nutrient deficiencies may also cause these symptoms as well, but you can help prevent them with proper care. Other problems that look like nutrient lockout include nutrient toxicity, nutrient burn, and pH lockout.

Nutrient Toxicity: Watch out!

The most common nutrient problem that looks like nutrient lockouts is nutrient toxicity. This means the plant has too much of a certain nutrient type for it to absorb properly or use efficiently enough to keep healthy growth going on your cannabis plants. Nutrients will show up in different parts of your plant in nutrient toxicity, but it will always be the same nutrient that is present to excess.


All plants need nutrients, but new growers tend to run into more problems due to their inexperience. One of the common problems is nutrient lockout. These nutrient problems are most often caused by nutrient deficiencies or nutrient toxicity, but nutrient lockout can also be caused by too much nutrient salts in the soil.

To fix nutrient lockout you will need to flush nutrient lockout plants with pure water that has no nutrient supplements in it. Once the nutrient lockout is fixed you should be careful about the nutrient supplements you are giving plants in the future.

Thank you for reading our article, should you have any further questions please see our articles about PH water and cannabis deficiencies.

To learn more about growing cannabis at home consider checking out our guides on: Getting Started, Troubleshooting, and Optimizing your Grow or search our Knowledge Base.

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