Cannabis Nutrient Lockout

If you’ve been nurturing and feeding your plants, but they don’t seem to be growing well, lockout could be the issue. It happens! Just like getting locked out of the house, most cannabis growers have gone through having, recognizing, and fixing cannabis nutrient lockout sat least once. You might be humbled by the experience, but it’s not the end of the world. 

Stick around to find out: 

• How to identify nutrient lockout symptoms in cannabis

• How to fix it

• How to stop nutrient lockout before it starts

What Is Cannabis Nutrient Lockout?

Cannabis nutrient lockout is when there’s plant food in the medium, but the roots can’t absorb it. Nutrient lockout happens when the pH of the area around the roots (for example, the soil) sways away from cannabis’s ideal range between 5.8 and 6.2

Think about it this way: we breathe oxygen, and we know that water has oxygen in it – it’s the “O” in H2O. But can you breathe water? I’ll wait. No? Ok. 

Maintaining the right pH in the area surrounding the roots is like having a universal key to all of their locks.

Nutrient Lockout vs. Deficiency

Cannabis Nutrient deficiency is a symptom of lockout. Cannabis nutrient lockout leads to deficiency because the plant isn’t getting what it needs, but it’s not due to underfeeding. By making that incorrect assumption, a lot of growers worsen their situation by feeding more nutrients that can create toxic imbalances and are ultimately wasted. The pH of your nutrient solution and substrate affect which nutrients are available, and each has its own ideal range. 

What Causes Cannabis Nutrient Lockout?

Outside of the narrow ideal pH range, many nutrients are still available, but deficiencies will show up eventually. As your cannabis experiences nutrient lockout, the deficiencies will appear progressively.  

Salt Buildup: Too Much of a Good Thing

Synthetic fertilizers contain compounds known as chemical salts. In water at the right pH they dissolve, the elements needed for growth separate from each other and are available to be absorbed by the plant. 

This is why nutrients are often sold as “A & B” solutions that you have to mix just before you feed them to your plants. Otherwise some of the ingredients would meet up and reorganize into strongly-bonded, unavailable forms. 

Unused nutrient salts that remain in the substrate can “build up” and later interfer,e causing issues with your pH, “locking out” your plant's ability to uptake nutrients. 

I recommend following a “feed, feed, water only” rotation to regularly flush salts out of your substrate.

Overwatering: Drowning Your Plants

Cannabis roots need access to air in the soil. When the substrate is waterlogged, the plant can’t feed itself properly. While not the same as a cannabis nutrient lockout, overwatering or underwatering are situations where the nutrients might be in good supply but can’t be used. 

Watch Out for Hard Water

Water is “hard” when it contains a lot of minerals (above 200 ppm). This affects pH, and those minerals can quickly interfere with the overall balance of the feed. Making sure you monitor the quality of your water is crucial for a successful homegrow.

Signs of Nutrient Lockout on Your Weed Plants

Cannabis nutrient lockout will affect your plants progressively. Below are some of its most important tell-tale signs.

Stunted Growth 

Soon enough, cannabis nutrient lockout forces plants to slow or even stop growing because they aren’t eating well. They don’t have enough of the building blocks they need to make new cells or do the other things (breathe, photosynthesize) that keep them alive. 

Stunted growth will happen before characteristics of individual nutrient problems show up, so if young plants aren’t growing as quickly as expected, seriously consider nutrient lockout as the possible cause. 

Yellowing Leaves (Chlorosis)

Some nutrients can get moved around inside a plant to where it needs them; others can’t. When experiencing a lockout, cannabis will try and use anything it’s stored up to continue growing. If one of these “mobile” nutrients (Nitrogen, Phosphorus, Potassium, and Magnesium) is locked out, the plant sacrifices its oldest leaves first. They turn yellow and drop off as the nutrient is carried away to where new growth is happening. 

Burnt Leaf Tips

Again, this is a sign that the plant is losing the battle against hunger. Crunchy, burnt-looking leaf tips are a symptom of sacrifice or deficiency. 

Leaf Discoloration and Curling

Cannabis leaves should be evenly bright green and lush. Any kind of warping, discoloration, or curling could be a sign of cannabis nutrient lockout.

How to Fix Nutrient Weed Plants after Nute Lockout

Until you’ve some practice identifying and resolving individual nutrient issues, it’s best to take a simple approach to fix cannabis nutrient lockout. 

Step 1: Stop Feeding and Test the pH

Put down the bottle and pick up the pen (or testing kit). When you’re supplying all the needed nutrients, but the plant is showing signs of deficiencies, chances are good that you’re out of the ideal pH range. 

You should aim to keep it between 5.5 and 6.5. In this zone, all of the most important nutrients are available. If you are using a digital meter for testing, you can optimize with a tighter range of 5.8-6.2. 

Tip: Get yourself a probe-style pH tester. Save yourself frustration and time that could be better spent inspecting your plants and building up data and knowledge rather than struggling with strips and solutions and wide margins of error. 

Step 2: Flush Your Growing Medium

“Flushing” is the name we use for rinsing built-up nutrients out of the growing medium. Pour plain, ph-adjusted water at 77°F/24°C through the substrate and allow it to drain. Do for the next two scheduled feedings with no added fertilizers. On the third, use ½-strength solution. 

In hydroponics systems, drain the reservoir and run it through with clean, pH-adjusted water to clear irrigation lines and rinse the roots. Return to feeding as usual and observe the plants. 

Flushing formulas (not to be confused with “finishing” solutions) that are made to “clean” or “clear” a substrate are available. They typically contain ingredients that dissolve built-up nutrients so that plain water flushes them more effectively away.  

Step 3: Adjust pH Levels

For the best picture of what’s going on in your rootzone, test what’s going in and what’s coming out – what drains out is called “runoff.” In containers, there should always be some amount of runoff when you feed your plants. 

Test pH in three stages: 

1. Test the water and see what you’re working with. Use a ‘pH up’ or ‘pH down’ solution and adjust it to 6. 
   

2. Test the nutrient solution after you mix it, according to the maker’s instructions, and adjust again to bring it into the 5.8-6.2 range. 
   

3. Test the moistened substrate and/or runoff. Using this measurement, you can make an adjustment in step 1 to account for how much the pH changed between steps 2 and 3. For example, if the pH of your runoff is lower than your fertilizer solution, make sure you “pH up” the initial solution.
   

Before you start messing around with the pH of your nutrient solution, double-check that you’re not simply over-feeding your plants. Follow the manufacturer’s instructions and application schedule, and don’t feel intimidated to call their helpline or email them with questions. It’s what they’re there for!

Safety Note: Be very careful when working with bottles of ‘pH up’ and ‘pH down’ solutions. Wear gloves and measure with pipettes instead of spoons to protect yourself from chemical burns. Always mix them into water before combining with your nutrients.

Step 4: Use Foliar Feeds for Quick Relief

Plants can absorb nutrients through their leaves too! Foliar feeding a weak solution of your scheduled nutrient can help keep plants fed while their substrates are being flushed. Check the manufacturer’s recommendations for mixing, because spraying with something too strong can cause more damage.  

Step 5: Switch to Chelated Nutrients

“Chelated” (pronounced “KEY-lated”) nutrients are engineered to keep essential minerals (e.g. calcium, iron, zinc, and copper) dissolved, for better nutrient absorption. 

Cannabis nutrient lockout-related deficiencies observed in new growth can often be helped by using chelated nutrients. 

How Long Does it Take for Plants to Recover from Cannabis Nutrient Lockout?

About a week depending on the damage. For faster recovery: 

• Remove damaged leaves starting from the bottom of the plant. Don’t take more than half of the total number of leaves until you see new healthy growth.   

• Examine and rinse roots, carefully trim damaged ones, and re-pot if the soil is too compacted.  

• Foliar-feed your plants

Preventing Cannabis Nutrient Lockout

Remember the “locked out of the house” scenario I described up top? Nutrient lockout often happens when growers act before they think. Little shortcuts don’t seem like a big deal in the moment, but can lead to stress for both you and your plants. 

Here are some ways to avoid nutrient lockout in the future:

• Test pH Regularly: Never assume your substrate’s pH is within the ideal range without testing it.

• Use High-Quality Nutrients

Good nutrients work with you to prevent lockout. If you are new to cultivation, keep it simple! Using quality products, made for growing cannabis, can save you from having to guess if your plant has access to the right amounts of its essential nutrients. 

Tip: Look for a brand that gives clear instructions. Some companies offer “self-buffering” nutrient solutions that help keep the mixture’s pH from changing quickly. 

• Avoid Overwatering and Overfeeding

More isn’t better. Cannabis grows well when it has what it needs, not excess – at best overfeeding is a waste, at worst, it causes stress and weakens your plants.

• Go Organic for Better Soil Health

For the best root zone health, choose OMRI (Organic Materials Review Institute)-certified nutrients and substrates or learn to make your own using organic methods. Add beneficial microbes (bacteria and fungi) according to the manufacturer’s instructions. These are your plant’s partners in making the most out of available nutrients and contribute a lot to the overall potential of your harvests. 

Nutrient Lockout in Different Growing Mediums

Nutrient lockout got your plants feeling down? Don't stress! This section's got the lowdown on how to fix it and keep your cannabis thriving in all mediums.

Soil, Coco/Coir and Rockwool

A soilless mix is what you’ll usually find at a garden centre when you’re looking to fill pots with a nice, user-friendly pre-mixed substrate. Bagged soils sometimes come “charged” with nutrients, (and/or beneficial microbes) already – check this before you start your grow cycle to prevent overfeeding and lockout. 

Always test the pH of a new batch of substrate before you use it. Performing this quality control step can save headaches later when you can’t figure out what’s to blame for weird post-feeding pH readings.

When using any of these, it’s a good habit to cycle pH-corrected water through the substrate on a rotation with your nutrient solution to avoid potential lockout.

“True” Soil

If you’re growing in “true” soil, which contains a mixture of dirt and organics like compost, worm castings, etc, nutrient lockout can happen if there is an imbalance in the pH or the mineral content. Beneficial bacteria and fungi help the plant access nutrients, but they also need the pH to be in the ideal range to thrive. Get help from your local agricultural extension to diagnose and resolve pH issues when growing in the ground. 

Rockwool and Water-Only Hydroponics

Make sure you’re filling your reservoirs with only the amount of nutrient solution that will be used within the next 7 days (or as recommended by the manufacturer). Temperature also affects nutrient availability, so keep tabs on this factor to prevent lockout.

Final Thoughts

Nutrient lockout is avoidable – but if it’s already happened, you can handle it. Being mindful, following nutrient-makers instructions, and maintaining good habits will go a long way to keeping your cannabis grow healthy and bountiful.

Until next time, may you and your gardens keep growing together, ever higher!