What are the Signs of Cannabis Nutrient Lockout and How to Fix it?

Nutrient lockout is one of the most common problems that growers can face. It can be frustrating, especially if you’re a beginning grower and you can’t figure out what is wrong.

Nutrient lockout is when nutrient elements like magnesium, zinc, iron, and even potassium are present in the root zone, but your plant can’t absorb them. It can happen in all growing mediums, but it’s more likely to occur in soil, coco coir, or rockwool.

When a plant is not being cared for properly there are warning signs. Things get tricky when plants demonstrate the same warning signs for multiple issues. Droopy branches and leaves, yellowing leaves, or drying out are common issues. These symptoms are signs of not only nutrient lockout, but under-watering, over-watering, wind burn, and general nutrient deficiencies. So how to tell what is happening within the plant is to first check that these others factors are not the problem.

  • are you under-watering your plants?
  • are you over-watering your plants?
  • do your plants have wind burn?
  • are your plants experiencing nutrient deficiencies?

Signs and Symptoms of Nutrients Build Up

nutrient lockout

Marijuana plants require numerous nutrients to grow and thrive. Aside from the ‘big three’ nutrients – nitrogen, phosphorus, and potassium – your crop also needs secondary nutrients and micronutrients. Examples of these include iron, zinc, copper, manganese, magnesium, and cobalt.

Early warning signs

  • An extreme deep green coloration to leaves
  • Bending at the tips of leaves
  • A slight yellowing or browning at the very tips of leaves

Nutrient burn symptoms start at the tips of the leaves because as excess nutrients build up, the plant attempts to pass them along, and the leaf tip is the furthest that they can move. Therefore, it’s important to keep a close eye on changes to a plant’s leaf tips to ensure nutrient burn is caught as early as possible.

Symptoms to worry about

As nutrient burn progresses, it’ll move from the very tips of the leaves back and inward. It’s this point that action must be taken in order to maintain a healthy plant, because nutrient burn left unchecked will continue to progress until entire leaves die and drop off.

Symptoms of advanced nutrient burn

  • Stunted growth
  • The foliage will turn yellow and become limp and lifeless.
  • Yellowing or browning moving back along the edges of the leaf
  • A yellowish halo separating the healthy tissue at the center of the leaf from the edges
  • Leaf edges curling under
  • Leaves twisting

While some or all of these symptoms will be present in a plant suffering from nutrient burn, curling leaves are often an indication of an overabundance of nitrogen, in specific. As soon as these more advanced symptoms are recognized, growers must isolate the nutrient burn and fix the source of the over-fertilization to prevent further damage.

How to Fix Nutrient Lockout?

It’s important to realize this happens even if you’re still feeding them like you’re supposed to using the proper feeding schedule. If your plants are experiencing a nutrient lockout, you must act fast to make the nutrients accessible. Otherwise, your plants will begin to suffer from nutrient deficiency and die.

The first step in remedying nutrient burn is to say goodbye to the parts of the plant that have already been affected. Nutrient burn can’t be reversed, and any leaves or buds that have already yellowed or browned are never going to be green again. Snipping off any damaged leaves and buds will prevent parts of the plant that have already been injured or died from rotting and causing further headaches

To remedy a mineral based lockout, flush the soil. This means watering the soil for an extended period of time to severely dilute the concentration of minerals or pH. Be sure to use pH neutral water when flooding your soil. This will allow for a clean reset and let the plants to come back into a safe and stable state.

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Preventing Nutrients Build Up


To prevent nutrient lockout from happening again, test the soil levels regularly. The importance of proper pH in growing can’t be overstated.

The optimal range (called the ‘sweet spot’) of pH for growing high-value indoor plants is 5.5–6.3. Keeping your plants in the ideal pH range is super important to avoid nutrient lockout.

pH imbalance remains a mystery to novice growers. The pH system is a measure of a substance’s alkalinity or acidity. The pH scale ranges from 0-14. 0 is the level of the most acidic substances on the table. 14 is the level of the most alkaline, and 7.0 is pH neutral. This is the value given to pure water.

If soil is your growing medium, the correct pH range is between 6.0 and 6.8. If you are using a hydroponics system, the best range is between 5.5 and 6.5. Your first duty is to monitor the pH of the water you use. If it is too alkaline, you encourage the growth of algae. If it is too acidic, you can ‘burn’ your crop.

Lighting should also be checked to ensure plants aren’t being under lit, as a plant getting less light generally won’t require the same level of nutrients. In that case, nutrient burn is actually a symptom of a lighting problem, and adjusting light levels will unlock additional nutrient capacity and better growth.

In order to keep plants at their ideal health, we would recommend routine flushes. At least once when moving into the flowering stage and again, about halfway through the flowering cycle.

Advanced growers invest in a Reverse Osmosis (RO) water system to handle that side of things. The amount of nutrients you add to your plants also alters the pH level. Nitrogen, for example, is very much on the acidic side. When you add it to pH neutral water, it should bring the pH down to the right level.

Always use organic nutrients. As well as being a better choice for the environment, organic nutrients will not cause a salt buildup. In contrast, chemical fertilizers are salt-based, which increases the likelihood of a nutrient lockout.

The key for growers looking to keep their crops healthy and to maximize growth is to constantly monitor their grow environments and to make adjustments based on the signs their plants give them. No matter the cannabis plant issue, you must learn from the experience. As crucial as it is to identify and solve nutrient lockout, knowing how to prevent it is even more critical. Whenever you plan to change your nutrient plan, do it gradually. 

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