Cannabis nutrient lockout can occur for various reasons, potentially harming plant health, development, and vitality. Nutrient lockout can happen at any stage of a cannabis plant’s life cycle, ranging from the seedling to the flowering stage.
In this article, I explain what causes cannabis nutrient lockout, tools and equipment to help prevent it from happening, the importance of correct pH management, signs of cannabis nutrient lockout, how to fix it, and the required recovery time.
What Is Nutrient Lockout in Cannabis and Weed Plants?
Cannabis plants require a consistent supply of primary and secondary nutrients, as well as trace minerals. Even where an optimal balance of available cannabis nutrients present, a plant’s ability to uptake nutrients will depend on the pH levels of the water and nutrient solution provided by the grower.
Common Causes of Nutrient Lockout in Weed and Cannabis Plants
Below is a brief list of all the reasons why a cannabis plant may experience nutrient lockout and how you can help prevent it from happening in the first place.
Hot Soils and Nutrient Imbalance in Cannabis Growing
This refers to a situation where a complete soil mix contains excessive nutrients, which can potentially burn plants, especially seedlings and freshly rooted clones. The pH of the rowing medium also has a significant effect on which nutrients become available.
For example, a peat-based growing substrate typically has a pH level of 3.0-5.0, which is acidic and falls outside the ideal range for maximum nutrient uptake.
Incorrect pH Levels and pH Lockout in Cannabis Plants
When growing organic cannabis, aim for a soil pH level between 5.5 and 7.0. Hydroponically grown cannabis requires a pH range between 5.5 and 6.5. The same rule applies to the water source and nutrient solution. Cannabis nutrient lockout occurs when the pH range is not consistent with the above value.
To check the pH level of the soil, use a pH meter that can be inserted into the soil. The other method is to use a digital pH pen or pH test strips to test the water or nutrient solution.
Nutrient Imbalance and Salt Build-Up Causing Lockout in Weed
When there are too many salts present in a growing medium, the result is a nutrient imbalance that will cause a cannabis nutrient lockout. The roots of a cannabis plant will be overwhelmed with the amount of salts present, affecting a plant’s ability to absorb specific nutrients over others. Nutrient imbalance can occur from over feeding cannabis plants.
Best Tools to Prevent Cannabis Nutrient Lockout and pH Lockout
Once you are aware of what causes a nutrient lockout in weed, the next step is to have the right tools and equipment present. Hence, you are in complete control and can effectively monitor pH levels and EC levels. Below is a list of the various tools and equipment available.
● A digital pH meter
● pH testing strip kit
● EC Pen (Electric Conductivity)
● pH Up product
● pH Down product
● Soil pH meter
How to Check pH Levels to Avoid Nutrient Lockout in Cannabis
To keep your plants as healthy as possible and ensure the optimal levels of available nutrients, you will need to check the pH levels of the water source, nutrient solution and growing medium.
How to Check Water pH to Prevent Cannabis Lockout
Use a digital pH pen and insert it into the water to check the value indicated on the pen. Tap water typically ranges from 6.5 to 8.0, depending on your location.
Testing Nutrient Solution pH to Avoid Lockout in Cannabis
After preparing your nutrient solution, insert the pH pen into the solution and verify the pH value. Using pH-up or pH-down products, you can adjust the pH accordingly.
Soil pH Testing to Prevent Nutrient Lockout in Weed Plants
pH meters are designed to be inserted into the soil or growing medium, with a meter on the front. You will be able to view real-time pH levels and determine if they need to be adjusted up or down.
Runoff pH Testing to Detect Cannabis Nutrient Lockout
When watering your plants with water or a nutrient solution, you can collect some of the runoff at the base of the pots. Inserting a pH pen will help you determine the difference between the starting pH level and the current pH level, allowing you to avoid cannabis nutrient lockout.
● 6.0 – 7.0 pH for Soil
● 5.5 – 6.5 pH for Hydroponics
Symptoms of Nutrient Lockout in Cannabis: Yellow Leaves, Curling, and Burn
You may not realise that you have a cannabis nutrient lockout until your plants start to display sure signs and symptoms. Below is a table to help you identify potential nutrient lockout issues and recognise cannabis leaf symptoms.
| Stunted Growth | The plants will slow down growing and may become stunted. Stunted growth can often occur during the flowering period, resulting in a lower yield. |
| Discoloured Leaves | Your once green and healthy leaves will shift to a yellow or brown colour. It will typically occur with older leaves before affecting the newest ones. |
| Wilting Leaves | The ends of the leaves will wilt downwards and lose vigour. |
| Curled Leaf Edges | The edges of the leaves may curl upwards. |
| Leaf Burn | The tips of the leaves will turn orange or brown, indicating tip burn. |
| Weak Plant Structure | Cannabis plants experiencing nutrient lockout will appear weak. In some cases, leaves will become brittle and begin to fall off. |
How to Fix Nutrient Lockout in Cannabis Plants During Flowering
If you have noticed that your cannabis plants are suffering from nutrient lockout, then you should act quickly. The best ways to fix a cannabis nutrient lockout are covered below.
Transplanting Cannabis Plants to Fix Nutrient Lockout
Re-potting cannabis seedlings or large plants from over-fertilised soil or growing medium will allow the plants to recover.
Flushing Cannabis Soil to Remove Nutrient Lockout
You should cut off the nutrient solution and flush the growing medium with pH-adjusted water. Once the undissolved salts have been washed away, you can begin feeding with a mild nutrient solution.
Adjusting pH to Fix pH Lockout in Cannabis Plants
The primary cause of a cannabis nutrient lockout is incorrect pH levels. Using pH-up or pH-down products will be the easiest and most practical way to maintain a constant pH level.
Recovery Time After Fixing Nutrient Lockout in Weed Plants
Once you have reported the plant into a pH-optimal growing medium with the ideal EC level or started to flush your plant, it should take between 7-10 days for nutrient lockout recovery.
Top Tips to Prevent Nutrient Lockout and pH Lockout in Weed Plants
Below are my top tips to consider for preventing cannabis nutrient lockout.
Avoid Chemical-Based Soil to Prevent Nutrient Lockout in Cannabis
It is best to avoid commercial garden centre-bought soils, as they are often over-fertilised and, in some cases, contain chemicals. Always check the NPK levels on the label and avoid anything with a ratio as high as 20-20-20. Buy a reliable substrate with balanced fertilizations like Atami’s ones.
Atami substrates are designed with the ideal balance between air and water, helping to prevent root problems. Choose from our extensive catalogue according to your needs, some examples are:
• Bi Grow Mix: ideal for moisture retention in dry climates.
• Janeco-Light-Mix or High Porosity Cocos: perfect if you need more drainage or work in humid areas.
Always Check Water pH to Prevent Lockout in Weed Plants
If you are using tap water, bottled water or reverse osmosis water, take the time to always check the pH levels before watering your plants.
Monitor Nutrient Runoff to Detect Cannabis Lockout
Getting into the habit of checking the runoff pH levels will let you know if there are too many salts in the growing medium. You will also see if you may need to flush the medium out or potentially translate.
Use a Cannabis Nutrient Feed Chart to Avoid Overfeeding and Lockout
Never guess how much nutrition you think plants need; instead, follow the feeding guide provided by the nutrient manufacturer. Cannabis plants require different electrical conductivity (EC) levels, so be extra careful not to over-fertilise seedlings and flowering plants.
Frequently Asked Questions
What is nutrient lockout in cannabis plants?
Nutrient lockout occurs when cannabis plants are unable to absorb essential nutrients from the soil or growing medium, even if those nutrients are present. This is often caused by incorrect pH levels, salt buildup, or nutrient imbalances.
How do I know if my cannabis plant has nutrient lockout?
Common signs include yellowing or browning leaves, stunted growth, curling leaf edges, tip burn, and weak plant structure. These symptoms often appear during the flowering stage and can resemble nutrient deficiencies.
What causes nutrient lockout during flowering?
During flowering, cannabis plants are more sensitive to pH fluctuations and overfeeding. Causes include:
• Incorrect pH levels
• Excess salts in the medium
• Over-fertilization
• Poor drainage or “hot” soil mixes
How can I fix nutrient lockout in weed plants?
You can fix nutrient lockout by:
• lushing the medium with pH-balanced water
• Adjusting pH levels using pH-up or pH-down products
• Transplanting into fresh, balanced soil
• Following a proper nutrient feed chart
What is the best pH range to prevent lockout in cannabis?
• Soil-grown cannabis: pH 6.0–7.0
• Hydroponic cannabis: pH 5.5–6.5
Maintaining consistent pH levels within these ranges helps prevent nutrient lockout.
Can nutrient lockout affect yield and bud quality?
Yes. If not addressed quickly, nutrient lockout can lead to reduced yields, poor bud development, and long-term damage to plant health.
How long does it take for cannabis plants to recover from nutrient lockout?
Recovery typically takes 7–10 days, depending on the severity and how quickly corrective actions are taken.
Final Thoughts on Preventing Nutrient Lockout in Cannabis
As long as you maintain pH levels between 5.5 and 7.0 for soil-based growth and 5.5 and 6.5 for hydroponics, you should not encounter any issues.
In the event you notice that your crop is suffering from a cannabis nutrient lockout, be prepared to act fast to avoid any long-term problems and potentially affect yields and the quality of the buds.
You should keep a pH pen in the grow room at all times and be as clinical and precise as possible and try creating a nutrient feeding plan.
