Have you ever found yourself staring at your plants, puzzled by signs of wilting or discoloration even though you give them good amounts of nutrients and love? Your plants may suffer from what is known as nutrient lockout or “nute lock” and it is one of the most frustrating obstacles that can plague novice and advanced growers.
On a personal level, I struggled with nute lock on some of my first runs and it took me some serious work to figure out what the issue was (there was no Google to consult at that time). I don’t want you to hit the same snags that I did so in this article I will cover the causes and common symptoms of nutrient lockout and I’ll teach you how to solve it.
What is Nutrient Lockout?
Nutrient lockout occurs when your plants are unable to absorb essential nutrients, regardless of their availability. Essentially, the substrate has enough nutrients but the plant is unable to receive the nutrients so they get underfed even though the nutes are present.
A nutrient lockout can lead to a range of symptoms, including stunted growth, yellow leaves, less flowering, and poor overall plant health. It can be caused by a variety of issues but most commonly it is due to.
- pH imbalances in the growing medium prevent the plant from absorbing one or more essential nutrients which can lead to a lockout. Cannabis plants prefer a pH of 6.0-7.0 in soil and 5.5-6.5 in hydroponic systems so keep a pH meter around in your grow.
- Over-fertilization of the plants where the substrate starts building up excessive salts and/or specific combinations and ratios of nutrients become incompatible.
How to Identify Nutrient Lockout Symptoms
Recognizing the signs of nutrient lockout can be tricky since they often resemble those of nutrient deficiencies. Symptoms are often exactly the same as nutrient deficiencies because the plant is in fact in a deficiency even though the substrate is not.
Here’s a rundown of the common symptoms that you should learn how to spot.
- Nitrogen Lockout – Yellowing of older leaves, followed by a gradual yellowing of the entire plant.
- Potassium Lockout – Yellowing of leaf margins, followed by browning and curling. Necrotic (dead) spots may also appear.
- Magnesium Lockout – Interveinal chlorosis (yellowing between veins) on older leaves, followed by reddening or purpling of leaf stems and veins.
- Signs of Low pH – Leaf tips and margins turning brown and curling upward on the cannabis plants.
- Signs of Salt Buildup – Stunted growth, leaf tip burn, and an overall decline in plant health with yellowing leaves and lost vigor.
How to Fix Nutrient Lockout
If you think you have an issue with nute lock, you need to take the necessary steps to correct the problem before it kills your batch.
Follow the 4 steps below and take notes on how your plants are improving (or not improving) so you learn for next time.
- Flush the Growing Medium – You need to remove excess salts and reset the pH of the substrate by flushing the growing medium with pH-balanced water. Flushing will remove salt buildup and excess nutrients so you can reapply a balanced nutrient solution. Add a gentle and cannabis specific nutrient system that is easy to use.
- Adjust the pH – Use a pH meter to test your substrate and adjust it to the optimal range. See the pH lockout chart below for guidance. A pH of 6.0-7.0 in soil and 5.5-6.5 in hydroponic systems is usually ideal for cannabis plants.
- Monitor Nutrient Levels – Carefully measure the nutrients you’re providing to avoid over-fertilization. Use high-quality nutrients and supplements to optimize plant health and to create a system that is easy for you to optimize in the long run. Some nutrient companies sell 6-parts or even 9-parts that are very difficult to work with and have too many risks. Organitek has a simple 2-part that is easy to use.
- Provide Supportive Nutrients – Consider introducing supportive nutrients in the form of additives and supplements to help your plants recover. For example, Amplify is a microbial inoculant that can help boost overall plant health by cycling nutrients with living organisms.
|Nutrient||Optimal pH Range|
|Nitrogen (N)||6.0 – 7.0|
|Potassium (K)||6.0 – 7.5|
|Magnesium (Mg)||6.0 – 7.5|
|Calcium (Ca)||6.2 – 7.5|
|Phosphorus (P)||6.0 – 7.5|
|Sulfur (S)||6.0 – 7.5|
|Iron (Fe)||6.0 – 6.5|
Preventing Nutrient Lockout From Happening Again
Now that you know how to spot the symptoms and correct the nutrient lock, you need to make adjustments to your future grows to make sure that it does not happen again.
- Keep a journal – You can learn a lot from your mistakes but only if you know and remember what they were. Keeping a journal with all the inputs and cycles that you give your plants is super important if you want to improve as a grower. A good journal will also help you perform single-variable tests that allow you to develop your own unique growing style.
- Keep an eye on the pH – Consistently monitor and adjust the pH of your nutrient solution, keeping it within the optimal range for your plants. Make this a habit that you never stray from. Some strains are more picky while other strains are more forgiving and ultimately, it’s your job to give all strains the optimal conditions for growth.
- Use a simple nutrient system – Don’t get suckered into a difficult 9-part fertilizer just because the labels look cool. Keep it simple with high-quality, easy-to-use systems like our Flower Republic 2-part. It is used and loved by both beginners and seasoned professionals with commercial facilities.
- Calibrate your equipment – Accurate and calibrated equipment (e.g., pH meters and EC meters) ensures precise monitoring and nutrient control. Don’t blindly trust the tools, but calibrate them regularly to ensure that they are showing accurate readings.
Use microbes to prevent a lockout
Whether you are a beginner or advanced gardener, you should consider adding microbes to your arsenal. Our microbial solution, Amplify, contains living organisms capable of delivering significant benefits to your garden.